// SPDX-License-Identifier: GPL-2.0-only
/*
 * ispstat.c
 *
 * TI OMAP3 ISP - Statistics core
 *
 * Copyright (C) 2010 Nokia Corporation
 * Copyright (C) 2009 Texas Instruments, Inc
 *
 * Contacts: David Cohen <dacohen@gmail.com>
 *           Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *           Sakari Ailus <sakari.ailus@iki.fi>
 */

#include <linux/dma-mapping.h>
#include <linux/slab.h>
#include <linux/timekeeping.h>
#include <linux/uaccess.h>

#include "isp.h"

#define ISP_STAT_USES_DMAENGINE(stat)   ((stat)->dma_ch != NULL)

/*
 * MAGIC_SIZE must always be the greatest common divisor of
 * AEWB_PACKET_SIZE and AF_PAXEL_SIZE.
 */
#define MAGIC_SIZE              16
#define MAGIC_NUM               0x55

/* HACK: AF module seems to be writing one more paxel data than it should. */
#define AF_EXTRA_DATA           OMAP3ISP_AF_PAXEL_SIZE

/*
 * HACK: H3A modules go to an invalid state after have a SBL overflow. It makes
 * the next buffer to start to be written in the same point where the overflow
 * occurred instead of the configured address. The only known way to make it to
 * go back to a valid state is having a valid buffer processing. Of course it
 * requires at least a doubled buffer size to avoid an access to invalid memory
 * region. But it does not fix everything. It may happen more than one
 * consecutive SBL overflows. In that case, it might be unpredictable how many
 * buffers the allocated memory should fit. For that case, a recover
 * configuration was created. It produces the minimum buffer size for each H3A
 * module and decrease the change for more SBL overflows. This recover state
 * will be enabled every time a SBL overflow occur. As the output buffer size
 * isn't big, it's possible to have an extra size able to fit many recover
 * buffers making it extreamily unlikely to have an access to invalid memory
 * region.
 */
#define NUM_H3A_RECOVER_BUFS    10

/*
 * HACK: Because of HW issues the generic layer sometimes need to have
 * different behaviour for different statistic modules.
 */
#define IS_H3A_AF(stat)         ((stat) == &(stat)->isp->isp_af)
#define IS_H3A_AEWB(stat)       ((stat) == &(stat)->isp->isp_aewb)
#define IS_H3A(stat)            (IS_H3A_AF(stat) || IS_H3A_AEWB(stat))

static void __isp_stat_buf_sync_magic(struct ispstat *stat,
                                      struct ispstat_buffer *buf,
                                      u32 buf_size, enum dma_data_direction dir,
                                      void (*dma_sync)(struct device *,
                                        dma_addr_t, unsigned long, size_t,
                                        enum dma_data_direction))
{
        /* Sync the initial and final magic words. */
        dma_sync(stat->isp->dev, buf->dma_addr, 0, MAGIC_SIZE, dir);
        dma_sync(stat->isp->dev, buf->dma_addr + (buf_size & PAGE_MASK),
                 buf_size & ~PAGE_MASK, MAGIC_SIZE, dir);
}

static void isp_stat_buf_sync_magic_for_device(struct ispstat *stat,
                                               struct ispstat_buffer *buf,
                                               u32 buf_size,
                                               enum dma_data_direction dir)
{
        if (ISP_STAT_USES_DMAENGINE(stat))
                return;

        __isp_stat_buf_sync_magic(stat, buf, buf_size, dir,
                                  dma_sync_single_range_for_device);
}

static void isp_stat_buf_sync_magic_for_cpu(struct ispstat *stat,
                                            struct ispstat_buffer *buf,
                                            u32 buf_size,
                                            enum dma_data_direction dir)
{
        if (ISP_STAT_USES_DMAENGINE(stat))
                return;

        __isp_stat_buf_sync_magic(stat, buf, buf_size, dir,
                                  dma_sync_single_range_for_cpu);
}

static int isp_stat_buf_check_magic(struct ispstat *stat,
                                    struct ispstat_buffer *buf)
{
        const u32 buf_size = IS_H3A_AF(stat) ?
                             buf->buf_size + AF_EXTRA_DATA : buf->buf_size;
        u8 *w;
        u8 *end;
        int ret = -EINVAL;

        isp_stat_buf_sync_magic_for_cpu(stat, buf, buf_size, DMA_FROM_DEVICE);

        /* Checking initial magic numbers. They shouldn't be here anymore. */
        for (w = buf->virt_addr, end = w + MAGIC_SIZE; w < end; w++)
                if (likely(*w != MAGIC_NUM))
                        ret = 0;

        if (ret) {
                dev_dbg(stat->isp->dev,
                        "%s: beginning magic check does not match.\n",
                        stat->subdev.name);
                return ret;
        }

        /* Checking magic numbers at the end. They must be still here. */
        for (w = buf->virt_addr + buf_size, end = w + MAGIC_SIZE;
             w < end; w++) {
                if (unlikely(*w != MAGIC_NUM)) {
                        dev_dbg(stat->isp->dev,
                                "%s: ending magic check does not match.\n",
                                stat->subdev.name);
                        return -EINVAL;
                }
        }

        isp_stat_buf_sync_magic_for_device(stat, buf, buf_size,
                                           DMA_FROM_DEVICE);

        return 0;
}

static void isp_stat_buf_insert_magic(struct ispstat *stat,
                                      struct ispstat_buffer *buf)
{
        const u32 buf_size = IS_H3A_AF(stat) ?
                             stat->buf_size + AF_EXTRA_DATA : stat->buf_size;

        isp_stat_buf_sync_magic_for_cpu(stat, buf, buf_size, DMA_FROM_DEVICE);

        /*
         * Inserting MAGIC_NUM at the beginning and end of the buffer.
         * buf->buf_size is set only after the buffer is queued. For now the
         * right buf_size for the current configuration is pointed by
         * stat->buf_size.
         */
        memset(buf->virt_addr, MAGIC_NUM, MAGIC_SIZE);
        memset(buf->virt_addr + buf_size, MAGIC_NUM, MAGIC_SIZE);

        isp_stat_buf_sync_magic_for_device(stat, buf, buf_size,
                                           DMA_BIDIRECTIONAL);
}

static void isp_stat_buf_sync_for_device(struct ispstat *stat,
                                         struct ispstat_buffer *buf)
{
        if (ISP_STAT_USES_DMAENGINE(stat))
                return;

        dma_sync_sgtable_for_device(stat->isp->dev, &buf->sgt, DMA_FROM_DEVICE);
}

static void isp_stat_buf_sync_for_cpu(struct ispstat *stat,
                                      struct ispstat_buffer *buf)
{
        if (ISP_STAT_USES_DMAENGINE(stat))
                return;

        dma_sync_sgtable_for_cpu(stat->isp->dev, &buf->sgt, DMA_FROM_DEVICE);
}

static void isp_stat_buf_clear(struct ispstat *stat)
{
        int i;

        for (i = 0; i < STAT_MAX_BUFS; i++)
                stat->buf[i].empty = 1;
}

static struct ispstat_buffer *
__isp_stat_buf_find(struct ispstat *stat, int look_empty)
{
        struct ispstat_buffer *found = NULL;
        int i;

        for (i = 0; i < STAT_MAX_BUFS; i++) {
                struct ispstat_buffer *curr = &stat->buf[i];

                /*
                 * Don't select the buffer which is being copied to
                 * userspace or used by the module.
                 */
                if (curr == stat->locked_buf || curr == stat->active_buf)
                        continue;

                /* Don't select uninitialised buffers if it's not required */
                if (!look_empty && curr->empty)
                        continue;

                /* Pick uninitialised buffer over anything else if look_empty */
                if (curr->empty) {
                        found = curr;
                        break;
                }

                /* Choose the oldest buffer */
                if (!found ||
                    (s32)curr->frame_number - (s32)found->frame_number < 0)
                        found = curr;
        }

        return found;
}

static inline struct ispstat_buffer *
isp_stat_buf_find_oldest(struct ispstat *stat)
{
        return __isp_stat_buf_find(stat, 0);
}

static inline struct ispstat_buffer *
isp_stat_buf_find_oldest_or_empty(struct ispstat *stat)
{
        return __isp_stat_buf_find(stat, 1);
}

static int isp_stat_buf_queue(struct ispstat *stat)
{
        if (!stat->active_buf)
                return STAT_NO_BUF;

        ktime_get_ts64(&stat->active_buf->ts);

        stat->active_buf->buf_size = stat->buf_size;
        if (isp_stat_buf_check_magic(stat, stat->active_buf)) {
                dev_dbg(stat->isp->dev, "%s: data wasn't properly written.\n",
                        stat->subdev.name);
                return STAT_NO_BUF;
        }
        stat->active_buf->config_counter = stat->config_counter;
        stat->active_buf->frame_number = stat->frame_number;
        stat->active_buf->empty = 0;
        stat->active_buf = NULL;

        return STAT_BUF_DONE;
}

/* Get next free buffer to write the statistics to and mark it active. */
static void isp_stat_buf_next(struct ispstat *stat)
{
        if (unlikely(stat->active_buf))
                /* Overwriting unused active buffer */
                dev_dbg(stat->isp->dev,
                        "%s: new buffer requested without queuing active one.\n",
                        stat->subdev.name);
        else
                stat->active_buf = isp_stat_buf_find_oldest_or_empty(stat);
}

static void isp_stat_buf_release(struct ispstat *stat)
{
        unsigned long flags;

        isp_stat_buf_sync_for_device(stat, stat->locked_buf);
        spin_lock_irqsave(&stat->isp->stat_lock, flags);
        stat->locked_buf = NULL;
        spin_unlock_irqrestore(&stat->isp->stat_lock, flags);
}

/* Get buffer to userspace. */
static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
                                               struct omap3isp_stat_data *data)
{
        int rval = 0;
        unsigned long flags;
        struct ispstat_buffer *buf;

        spin_lock_irqsave(&stat->isp->stat_lock, flags);

        while (1) {
                buf = isp_stat_buf_find_oldest(stat);
                if (!buf) {
                        spin_unlock_irqrestore(&stat->isp->stat_lock, flags);
                        dev_dbg(stat->isp->dev, "%s: cannot find a buffer.\n",
                                stat->subdev.name);
                        return ERR_PTR(-EBUSY);
                }
                if (isp_stat_buf_check_magic(stat, buf)) {
                        dev_dbg(stat->isp->dev,
                                "%s: current buffer has corrupted data\n.",
                                stat->subdev.name);
                        /* Mark empty because it doesn't have valid data. */
                        buf->empty = 1;
                } else {
                        /* Buffer isn't corrupted. */
                        break;
                }
        }

        stat->locked_buf = buf;

        spin_unlock_irqrestore(&stat->isp->stat_lock, flags);

        if (buf->buf_size > data->buf_size) {
                dev_warn(stat->isp->dev,
                         "%s: userspace's buffer size is not enough.\n",
                         stat->subdev.name);
                isp_stat_buf_release(stat);
                return ERR_PTR(-EINVAL);
        }

        isp_stat_buf_sync_for_cpu(stat, buf);

        rval = copy_to_user(data->buf,
                            buf->virt_addr,
                            buf->buf_size);

        if (rval) {
                dev_info(stat->isp->dev,
                         "%s: failed copying %d bytes of stat data\n",
                         stat->subdev.name, rval);
                buf = ERR_PTR(-EFAULT);
                isp_stat_buf_release(stat);
        }

        return buf;
}

static void isp_stat_bufs_free(struct ispstat *stat)
{
        struct device *dev = ISP_STAT_USES_DMAENGINE(stat)
                           ? NULL : stat->isp->dev;
        unsigned int i;

        for (i = 0; i < STAT_MAX_BUFS; i++) {
                struct ispstat_buffer *buf = &stat->buf[i];

                if (!buf->virt_addr)
                        continue;

                sg_free_table(&buf->sgt);

                dma_free_coherent(dev, stat->buf_alloc_size, buf->virt_addr,
                                  buf->dma_addr);

                buf->dma_addr = 0;
                buf->virt_addr = NULL;
                buf->empty = 1;
        }

        dev_dbg(stat->isp->dev, "%s: all buffers were freed.\n",
                stat->subdev.name);

        stat->buf_alloc_size = 0;
        stat->active_buf = NULL;
}

static int isp_stat_bufs_alloc_one(struct device *dev,
                                   struct ispstat_buffer *buf,
                                   unsigned int size)
{
        int ret;

        buf->virt_addr = dma_alloc_coherent(dev, size, &buf->dma_addr,
                                            GFP_KERNEL);
        if (!buf->virt_addr)
                return -ENOMEM;

        ret = dma_get_sgtable(dev, &buf->sgt, buf->virt_addr, buf->dma_addr,
                              size);
        if (ret < 0) {
                dma_free_coherent(dev, size, buf->virt_addr, buf->dma_addr);
                buf->virt_addr = NULL;
                buf->dma_addr = 0;
                return ret;
        }

        return 0;
}

/*
 * The device passed to the DMA API depends on whether the statistics block uses
 * ISP DMA, external DMA or PIO to transfer data.
 *
 * The first case (for the AEWB and AF engines) passes the ISP device, resulting
 * in the DMA buffers being mapped through the ISP IOMMU.
 *
 * The second case (for the histogram engine) should pass the DMA engine device.
 * As that device isn't accessible through the OMAP DMA engine API the driver
 * passes NULL instead, resulting in the buffers being mapped directly as
 * physical pages.
 *
 * The third case (for the histogram engine) doesn't require any mapping. The
 * buffers could be allocated with kmalloc/vmalloc, but we still use
 * dma_alloc_coherent() for consistency purpose.
 */
static int isp_stat_bufs_alloc(struct ispstat *stat, u32 size)
{
        struct device *dev = ISP_STAT_USES_DMAENGINE(stat)
                           ? NULL : stat->isp->dev;
        unsigned long flags;
        unsigned int i;

        spin_lock_irqsave(&stat->isp->stat_lock, flags);

        BUG_ON(stat->locked_buf != NULL);

        /* Are the old buffers big enough? */
        if (stat->buf_alloc_size >= size) {
                spin_unlock_irqrestore(&stat->isp->stat_lock, flags);
                return 0;
        }

        if (stat->state != ISPSTAT_DISABLED || stat->buf_processing) {
                dev_info(stat->isp->dev,
                         "%s: trying to allocate memory when busy\n",
                         stat->subdev.name);
                spin_unlock_irqrestore(&stat->isp->stat_lock, flags);
                return -EBUSY;
        }

        spin_unlock_irqrestore(&stat->isp->stat_lock, flags);

        isp_stat_bufs_free(stat);

        stat->buf_alloc_size = size;

        for (i = 0; i < STAT_MAX_BUFS; i++) {
                struct ispstat_buffer *buf = &stat->buf[i];
                int ret;

                ret = isp_stat_bufs_alloc_one(dev, buf, size);
                if (ret < 0) {
                        dev_err(stat->isp->dev,
                                "%s: Failed to allocate DMA buffer %u\n",
                                stat->subdev.name, i);
                        isp_stat_bufs_free(stat);
                        return ret;
                }

                buf->empty = 1;

                dev_dbg(stat->isp->dev,
                        "%s: buffer[%u] allocated. dma=%pad virt=%p",
                        stat->subdev.name, i, &buf->dma_addr, buf->virt_addr);
        }

        return 0;
}

static void isp_stat_queue_event(struct ispstat *stat, int err)
{
        struct video_device *vdev = stat->subdev.devnode;
        struct v4l2_event event;
        struct omap3isp_stat_event_status *status = (void *)event.u.data;

        memset(&event, 0, sizeof(event));
        if (!err) {
                status->frame_number = stat->frame_number;
                status->config_counter = stat->config_counter;
        } else {
                status->buf_err = 1;
        }
        event.type = stat->event_type;
        v4l2_event_queue(vdev, &event);
}


/*
 * omap3isp_stat_request_statistics - Request statistics.
 * @data: Pointer to return statistics data.
 *
 * Returns 0 if successful.
 */
int omap3isp_stat_request_statistics(struct ispstat *stat,
                                     struct omap3isp_stat_data *data)
{
        struct ispstat_buffer *buf;

        if (stat->state != ISPSTAT_ENABLED) {
                dev_dbg(stat->isp->dev, "%s: engine not enabled.\n",
                        stat->subdev.name);
                return -EINVAL;
        }

        mutex_lock(&stat->ioctl_lock);
        buf = isp_stat_buf_get(stat, data);
        if (IS_ERR(buf)) {
                mutex_unlock(&stat->ioctl_lock);
                return PTR_ERR(buf);
        }

        data->ts.tv_sec = buf->ts.tv_sec;
        data->ts.tv_usec = buf->ts.tv_nsec / NSEC_PER_USEC;
        data->config_counter = buf->config_counter;
        data->frame_number = buf->frame_number;
        data->buf_size = buf->buf_size;

        buf->empty = 1;
        isp_stat_buf_release(stat);
        mutex_unlock(&stat->ioctl_lock);

        return 0;
}

int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
                                        struct omap3isp_stat_data_time32 *data)
{
        struct omap3isp_stat_data data64 = { };
        int ret;

        ret = omap3isp_stat_request_statistics(stat, &data64);
        if (ret)
                return ret;

        data->ts.tv_sec = data64.ts.tv_sec;
        data->ts.tv_usec = data64.ts.tv_usec;
        data->buf = (uintptr_t)data64.buf;
        memcpy(&data->frame, &data64.frame, sizeof(data->frame));

        return 0;
}

/*
 * omap3isp_stat_config - Receives new statistic engine configuration.
 * @new_conf: Pointer to config structure.
 *
 * Returns 0 if successful, -EINVAL if new_conf pointer is NULL, -ENOMEM if
 * was unable to allocate memory for the buffer, or other errors if parameters
 * are invalid.
 */
int omap3isp_stat_config(struct ispstat *stat, void *new_conf)
{
        int ret;
        unsigned long irqflags;
        struct ispstat_generic_config *user_cfg = new_conf;
        u32 buf_size = user_cfg->buf_size;

        mutex_lock(&stat->ioctl_lock);

        dev_dbg(stat->isp->dev,
                "%s: configuring module with buffer size=0x%08lx\n",
                stat->subdev.name, (unsigned long)buf_size);

        ret = stat->ops->validate_params(stat, new_conf);
        if (ret) {
                mutex_unlock(&stat->ioctl_lock);
                dev_dbg(stat->isp->dev, "%s: configuration values are invalid.\n",
                        stat->subdev.name);
                return ret;
        }

        if (buf_size != user_cfg->buf_size)
                dev_dbg(stat->isp->dev,
                        "%s: driver has corrected buffer size request to 0x%08lx\n",
                        stat->subdev.name,
                        (unsigned long)user_cfg->buf_size);

        /*
         * Hack: H3A modules may need a doubled buffer size to avoid access
         * to a invalid memory address after a SBL overflow.
         * The buffer size is always PAGE_ALIGNED.
         * Hack 2: MAGIC_SIZE is added to buf_size so a magic word can be
         * inserted at the end to data integrity check purpose.
         * Hack 3: AF module writes one paxel data more than it should, so
         * the buffer allocation must consider it to avoid invalid memory
         * access.
         * Hack 4: H3A need to allocate extra space for the recover state.
         */
        if (IS_H3A(stat)) {
                buf_size = user_cfg->buf_size * 2 + MAGIC_SIZE;
                if (IS_H3A_AF(stat))
                        /*
                         * Adding one extra paxel data size for each recover
                         * buffer + 2 regular ones.
                         */
                        buf_size += AF_EXTRA_DATA * (NUM_H3A_RECOVER_BUFS + 2);
                if (stat->recover_priv) {
                        struct ispstat_generic_config *recover_cfg =
                                stat->recover_priv;
                        buf_size += recover_cfg->buf_size *
                                    NUM_H3A_RECOVER_BUFS;
                }
                buf_size = PAGE_ALIGN(buf_size);
        } else { /* Histogram */
                buf_size = PAGE_ALIGN(user_cfg->buf_size + MAGIC_SIZE);
        }

        ret = isp_stat_bufs_alloc(stat, buf_size);
        if (ret) {
                mutex_unlock(&stat->ioctl_lock);
                return ret;
        }

        spin_lock_irqsave(&stat->isp->stat_lock, irqflags);
        stat->ops->set_params(stat, new_conf);
        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);

        /*
         * Returning the right future config_counter for this setup, so
         * userspace can *know* when it has been applied.
         */
        user_cfg->config_counter = stat->config_counter + stat->inc_config;

        /* Module has a valid configuration. */
        stat->configured = 1;
        dev_dbg(stat->isp->dev,
                "%s: module has been successfully configured.\n",
                stat->subdev.name);

        mutex_unlock(&stat->ioctl_lock);

        return 0;
}

/*
 * isp_stat_buf_process - Process statistic buffers.
 * @buf_state: points out if buffer is ready to be processed. It's necessary
 *             because histogram needs to copy the data from internal memory
 *             before be able to process the buffer.
 */
static int isp_stat_buf_process(struct ispstat *stat, int buf_state)
{
        int ret = STAT_NO_BUF;

        if (!atomic_add_unless(&stat->buf_err, -1, 0) &&
            buf_state == STAT_BUF_DONE && stat->state == ISPSTAT_ENABLED) {
                ret = isp_stat_buf_queue(stat);
                isp_stat_buf_next(stat);
        }

        return ret;
}

int omap3isp_stat_pcr_busy(struct ispstat *stat)
{
        return stat->ops->busy(stat);
}

int omap3isp_stat_busy(struct ispstat *stat)
{
        return omap3isp_stat_pcr_busy(stat) | stat->buf_processing |
                (stat->state != ISPSTAT_DISABLED);
}

/*
 * isp_stat_pcr_enable - Disables/Enables statistic engines.
 * @pcr_enable: 0/1 - Disables/Enables the engine.
 *
 * Must be called from ISP driver when the module is idle and synchronized
 * with CCDC.
 */
static void isp_stat_pcr_enable(struct ispstat *stat, u8 pcr_enable)
{
        if ((stat->state != ISPSTAT_ENABLING &&
             stat->state != ISPSTAT_ENABLED) && pcr_enable)
                /* Userspace has disabled the module. Aborting. */
                return;

        stat->ops->enable(stat, pcr_enable);
        if (stat->state == ISPSTAT_DISABLING && !pcr_enable)
                stat->state = ISPSTAT_DISABLED;
        else if (stat->state == ISPSTAT_ENABLING && pcr_enable)
                stat->state = ISPSTAT_ENABLED;
}

void omap3isp_stat_suspend(struct ispstat *stat)
{
        unsigned long flags;

        spin_lock_irqsave(&stat->isp->stat_lock, flags);

        if (stat->state != ISPSTAT_DISABLED)
                stat->ops->enable(stat, 0);
        if (stat->state == ISPSTAT_ENABLED)
                stat->state = ISPSTAT_SUSPENDED;

        spin_unlock_irqrestore(&stat->isp->stat_lock, flags);
}

void omap3isp_stat_resume(struct ispstat *stat)
{
        /* Module will be re-enabled with its pipeline */
        if (stat->state == ISPSTAT_SUSPENDED)
                stat->state = ISPSTAT_ENABLING;
}

static void isp_stat_try_enable(struct ispstat *stat)
{
        unsigned long irqflags;

        if (stat->priv == NULL)
                /* driver wasn't initialised */
                return;

        spin_lock_irqsave(&stat->isp->stat_lock, irqflags);
        if (stat->state == ISPSTAT_ENABLING && !stat->buf_processing &&
            stat->buf_alloc_size) {
                /*
                 * Userspace's requested to enable the engine but it wasn't yet.
                 * Let's do that now.
                 */
                stat->update = 1;
                isp_stat_buf_next(stat);
                stat->ops->setup_regs(stat, stat->priv);
                isp_stat_buf_insert_magic(stat, stat->active_buf);

                /*
                 * H3A module has some hw issues which forces the driver to
                 * ignore next buffers even if it was disabled in the meantime.
                 * On the other hand, Histogram shouldn't ignore buffers anymore
                 * if it's being enabled.
                 */
                if (!IS_H3A(stat))
                        atomic_set(&stat->buf_err, 0);

                isp_stat_pcr_enable(stat, 1);
                spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                dev_dbg(stat->isp->dev, "%s: module is enabled.\n",
                        stat->subdev.name);
        } else {
                spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
        }
}

void omap3isp_stat_isr_frame_sync(struct ispstat *stat)
{
        isp_stat_try_enable(stat);
}

void omap3isp_stat_sbl_overflow(struct ispstat *stat)
{
        unsigned long irqflags;

        spin_lock_irqsave(&stat->isp->stat_lock, irqflags);
        /*
         * Due to a H3A hw issue which prevents the next buffer to start from
         * the correct memory address, 2 buffers must be ignored.
         */
        atomic_set(&stat->buf_err, 2);

        /*
         * If more than one SBL overflow happen in a row, H3A module may access
         * invalid memory region.
         * stat->sbl_ovl_recover is set to tell to the driver to temporarily use
         * a soft configuration which helps to avoid consecutive overflows.
         */
        if (stat->recover_priv)
                stat->sbl_ovl_recover = 1;
        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
}

/*
 * omap3isp_stat_enable - Disable/Enable statistic engine as soon as possible
 * @enable: 0/1 - Disables/Enables the engine.
 *
 * Client should configure all the module registers before this.
 * This function can be called from a userspace request.
 */
int omap3isp_stat_enable(struct ispstat *stat, u8 enable)
{
        unsigned long irqflags;

        dev_dbg(stat->isp->dev, "%s: user wants to %s module.\n",
                stat->subdev.name, enable ? "enable" : "disable");

        /* Prevent enabling while configuring */
        mutex_lock(&stat->ioctl_lock);

        spin_lock_irqsave(&stat->isp->stat_lock, irqflags);

        if (!stat->configured && enable) {
                spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                mutex_unlock(&stat->ioctl_lock);
                dev_dbg(stat->isp->dev,
                        "%s: cannot enable module as it's never been successfully configured so far.\n",
                        stat->subdev.name);
                return -EINVAL;
        }

        if (enable) {
                if (stat->state == ISPSTAT_DISABLING)
                        /* Previous disabling request wasn't done yet */
                        stat->state = ISPSTAT_ENABLED;
                else if (stat->state == ISPSTAT_DISABLED)
                        /* Module is now being enabled */
                        stat->state = ISPSTAT_ENABLING;
        } else {
                if (stat->state == ISPSTAT_ENABLING) {
                        /* Previous enabling request wasn't done yet */
                        stat->state = ISPSTAT_DISABLED;
                } else if (stat->state == ISPSTAT_ENABLED) {
                        /* Module is now being disabled */
                        stat->state = ISPSTAT_DISABLING;
                        isp_stat_buf_clear(stat);
                }
        }

        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
        mutex_unlock(&stat->ioctl_lock);

        return 0;
}

int omap3isp_stat_s_stream(struct v4l2_subdev *subdev, int enable)
{
        struct ispstat *stat = v4l2_get_subdevdata(subdev);

        if (enable) {
                /*
                 * Only set enable PCR bit if the module was previously
                 * enabled through ioctl.
                 */
                isp_stat_try_enable(stat);
        } else {
                unsigned long flags;
                /* Disable PCR bit and config enable field */
                omap3isp_stat_enable(stat, 0);
                spin_lock_irqsave(&stat->isp->stat_lock, flags);
                stat->ops->enable(stat, 0);
                spin_unlock_irqrestore(&stat->isp->stat_lock, flags);

                /*
                 * If module isn't busy, a new interrupt may come or not to
                 * set the state to DISABLED. As Histogram needs to read its
                 * internal memory to clear it, let interrupt handler
                 * responsible of changing state to DISABLED. If the last
                 * interrupt is coming, it's still safe as the handler will
                 * ignore the second time when state is already set to DISABLED.
                 * It's necessary to synchronize Histogram with streamoff, once
                 * the module may be considered idle before last SDMA transfer
                 * starts if we return here.
                 */
                if (!omap3isp_stat_pcr_busy(stat))
                        omap3isp_stat_isr(stat);

                dev_dbg(stat->isp->dev, "%s: module is being disabled\n",
                        stat->subdev.name);
        }

        return 0;
}

/*
 * __stat_isr - Interrupt handler for statistic drivers
 */
static void __stat_isr(struct ispstat *stat, int from_dma)
{
        int ret = STAT_BUF_DONE;
        int buf_processing;
        unsigned long irqflags;
        struct isp_pipeline *pipe;

        /*
         * stat->buf_processing must be set before disable module. It's
         * necessary to not inform too early the buffers aren't busy in case
         * of SDMA is going to be used.
         */
        spin_lock_irqsave(&stat->isp->stat_lock, irqflags);
        if (stat->state == ISPSTAT_DISABLED) {
                spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                return;
        }
        buf_processing = stat->buf_processing;
        stat->buf_processing = 1;
        stat->ops->enable(stat, 0);

        if (buf_processing && !from_dma) {
                if (stat->state == ISPSTAT_ENABLED) {
                        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                        dev_err(stat->isp->dev,
                                "%s: interrupt occurred when module was still processing a buffer.\n",
                                stat->subdev.name);
                        ret = STAT_NO_BUF;
                        goto out;
                } else {
                        /*
                         * Interrupt handler was called from streamoff when
                         * the module wasn't busy anymore to ensure it is being
                         * disabled after process last buffer. If such buffer
                         * processing has already started, no need to do
                         * anything else.
                         */
                        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                        return;
                }
        }
        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);

        /* If it's busy we can't process this buffer anymore */
        if (!omap3isp_stat_pcr_busy(stat)) {
                if (!from_dma && stat->ops->buf_process)
                        /* Module still need to copy data to buffer. */
                        ret = stat->ops->buf_process(stat);
                if (ret == STAT_BUF_WAITING_DMA)
                        /* Buffer is not ready yet */
                        return;

                spin_lock_irqsave(&stat->isp->stat_lock, irqflags);

                /*
                 * Histogram needs to read its internal memory to clear it
                 * before be disabled. For that reason, common statistic layer
                 * can return only after call stat's buf_process() operator.
                 */
                if (stat->state == ISPSTAT_DISABLING) {
                        stat->state = ISPSTAT_DISABLED;
                        spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
                        stat->buf_processing = 0;
                        return;
                }
                pipe = to_isp_pipeline(&stat->subdev.entity);
                stat->frame_number = atomic_read(&pipe->frame_number);

                /*
                 * Before this point, 'ret' stores the buffer's status if it's
                 * ready to be processed. Afterwards, it holds the status if
                 * it was processed successfully.
                 */
                ret = isp_stat_buf_process(stat, ret);

                if (likely(!stat->sbl_ovl_recover)) {
                        stat->ops->setup_regs(stat, stat->priv);
                } else {
                        /*
                         * Using recover config to increase the chance to have
                         * a good buffer processing and make the H3A module to
                         * go back to a valid state.
                         */
                        stat->update = 1;
                        stat->ops->setup_regs(stat, stat->recover_priv);
                        stat->sbl_ovl_recover = 0;

                        /*
                         * Set 'update' in case of the module needs to use
                         * regular configuration after next buffer.
                         */
                        stat->update = 1;
                }

                isp_stat_buf_insert_magic(stat, stat->active_buf);

                /*
                 * Hack: H3A modules may access invalid memory address or send
                 * corrupted data to userspace if more than 1 SBL overflow
                 * happens in a row without re-writing its buffer's start memory
                 * address in the meantime. Such situation is avoided if the
                 * module is not immediately re-enabled when the ISR misses the
                 * timing to process the buffer and to setup the registers.
                 * Because of that, pcr_enable(1) was moved to inside this 'if'
                 * block. But the next interruption will still happen as during
                 * pcr_enable(0) the module was busy.
                 */
                isp_stat_pcr_enable(stat, 1);
                spin_unlock_irqrestore(&stat->isp->stat_lock, irqflags);
        } else {
                /*
                 * If a SBL overflow occurs and the H3A driver misses the timing
                 * to process the buffer, stat->buf_err is set and won't be
                 * cleared now. So the next buffer will be correctly ignored.
                 * It's necessary due to a hw issue which makes the next H3A
                 * buffer to start from the memory address where the previous
                 * one stopped, instead of start where it was configured to.
                 * Do not "stat->buf_err = 0" here.
                 */

                if (stat->ops->buf_process)
                        /*
                         * Driver may need to erase current data prior to
                         * process a new buffer. If it misses the timing, the
                         * next buffer might be wrong. So should be ignored.
                         * It happens only for Histogram.
                         */
                        atomic_set(&stat->buf_err, 1);

                ret = STAT_NO_BUF;
                dev_dbg(stat->isp->dev,
                        "%s: cannot process buffer, device is busy.\n",
                        stat->subdev.name);
        }

out:
        stat->buf_processing = 0;
        isp_stat_queue_event(stat, ret != STAT_BUF_DONE);
}

void omap3isp_stat_isr(struct ispstat *stat)
{
        __stat_isr(stat, 0);
}

void omap3isp_stat_dma_isr(struct ispstat *stat)
{
        __stat_isr(stat, 1);
}

int omap3isp_stat_subscribe_event(struct v4l2_subdev *subdev,
                                  struct v4l2_fh *fh,
                                  struct v4l2_event_subscription *sub)
{
        struct ispstat *stat = v4l2_get_subdevdata(subdev);

        if (sub->type != stat->event_type)
                return -EINVAL;

        return v4l2_event_subscribe(fh, sub, STAT_NEVENTS, NULL);
}

void omap3isp_stat_unregister_entities(struct ispstat *stat)
{
        v4l2_device_unregister_subdev(&stat->subdev);
}

int omap3isp_stat_register_entities(struct ispstat *stat,
                                    struct v4l2_device *vdev)
{
        stat->subdev.dev = vdev->mdev->dev;

        return v4l2_device_register_subdev(vdev, &stat->subdev);
}

static int isp_stat_init_entities(struct ispstat *stat, const char *name,
                                  const struct v4l2_subdev_ops *sd_ops)
{
        struct v4l2_subdev *subdev = &stat->subdev;
        struct media_entity *me = &subdev->entity;

        v4l2_subdev_init(subdev, sd_ops);
        snprintf(subdev->name, sizeof(subdev->name), "OMAP3 ISP %s", name);
        subdev->grp_id = BIT(16);       /* group ID for isp subdevs */
        subdev->flags |= V4L2_SUBDEV_FL_HAS_EVENTS | V4L2_SUBDEV_FL_HAS_DEVNODE;
        v4l2_set_subdevdata(subdev, stat);

        stat->pad.flags = MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_MUST_CONNECT;
        me->ops = NULL;
        me->function = MEDIA_ENT_F_PROC_VIDEO_STATISTICS;

        return media_entity_pads_init(me, 1, &stat->pad);
}

int omap3isp_stat_init(struct ispstat *stat, const char *name,
                       const struct v4l2_subdev_ops *sd_ops)
{
        int ret;

        stat->buf = kzalloc_objs(*stat->buf, STAT_MAX_BUFS);
        if (!stat->buf)
                return -ENOMEM;

        isp_stat_buf_clear(stat);
        mutex_init(&stat->ioctl_lock);
        atomic_set(&stat->buf_err, 0);

        ret = isp_stat_init_entities(stat, name, sd_ops);
        if (ret < 0) {
                mutex_destroy(&stat->ioctl_lock);
                kfree(stat->buf);
        }

        return ret;
}

void omap3isp_stat_cleanup(struct ispstat *stat)
{
        media_entity_cleanup(&stat->subdev.entity);
        mutex_destroy(&stat->ioctl_lock);
        isp_stat_bufs_free(stat);
        kfree(stat->buf);
        kfree(stat->priv);
        kfree(stat->recover_priv);
}