// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Management Interface (SCMI) Message SMC/HVC
 * Transport driver
 *
 * Copyright 2020 NXP
 */

#include <linux/arm-smccc.h>
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/limits.h>
#include <linux/platform_device.h>
#include <linux/processor.h>
#include <linux/slab.h>

#include "../common.h"

/*
 * The shmem address is split into 4K page and offset.
 * This is to make sure the parameters fit in 32bit arguments of the
 * smc/hvc call to keep it uniform across smc32/smc64 conventions.
 * This however limits the shmem address to 44 bit.
 *
 * These optional parameters can be used to distinguish among multiple
 * scmi instances that are using the same smc-id.
 * The page parameter is passed in r1/x1/w1 register and the offset parameter
 * is passed in r2/x2/w2 register.
 */

#define SHMEM_SIZE (SZ_4K)
#define SHMEM_SHIFT 12
#define SHMEM_PAGE(x) (_UL((x) >> SHMEM_SHIFT))
#define SHMEM_OFFSET(x) ((x) & (SHMEM_SIZE - 1))

/**
 * struct scmi_smc - Structure representing a SCMI smc transport
 *
 * @irq: An optional IRQ for completion
 * @cinfo: SCMI channel info
 * @shmem: Transmit/Receive shared memory area
 * @io_ops: Transport specific I/O operations
 * @shmem_lock: Lock to protect access to Tx/Rx shared memory area.
 *              Used when NOT operating in atomic mode.
 * @inflight: Atomic flag to protect access to Tx/Rx shared memory area.
 *            Used when operating in atomic mode.
 * @func_id: smc/hvc call function id
 * @param_page: 4K page number of the shmem channel
 * @param_offset: Offset within the 4K page of the shmem channel
 * @cap_id: smc/hvc doorbell's capability id to be used on Qualcomm virtual
 *          platforms
 */

struct scmi_smc {
        int irq;
        struct scmi_chan_info *cinfo;
        struct scmi_shared_mem __iomem *shmem;
        struct scmi_shmem_io_ops *io_ops;
        /* Protect access to shmem area */
        struct mutex shmem_lock;
#define INFLIGHT_NONE   MSG_TOKEN_MAX
        atomic_t inflight;
        unsigned long func_id;
        unsigned long param_page;
        unsigned long param_offset;
        unsigned long cap_id;
};

static struct scmi_transport_core_operations *core;

static irqreturn_t smc_msg_done_isr(int irq, void *data)
{
        struct scmi_smc *scmi_info = data;

        core->rx_callback(scmi_info->cinfo,
                          core->shmem->read_header(scmi_info->shmem), NULL);

        return IRQ_HANDLED;
}

static bool smc_chan_available(struct device_node *of_node, int idx)
{
        struct device_node *np __free(device_node) =
                                        of_parse_phandle(of_node, "shmem", 0);
        if (!np)
                return false;

        return true;
}

static inline void smc_channel_lock_init(struct scmi_smc *scmi_info)
{
        if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
                atomic_set(&scmi_info->inflight, INFLIGHT_NONE);
        else
                mutex_init(&scmi_info->shmem_lock);
}

static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight)
{
        int ret;

        ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq);

        return ret == INFLIGHT_NONE;
}

static inline void
smc_channel_lock_acquire(struct scmi_smc *scmi_info,
                         struct scmi_xfer *xfer __maybe_unused)
{
        if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
                spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight));
        else
                mutex_lock(&scmi_info->shmem_lock);
}

static inline void smc_channel_lock_release(struct scmi_smc *scmi_info)
{
        if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
                atomic_set(&scmi_info->inflight, INFLIGHT_NONE);
        else
                mutex_unlock(&scmi_info->shmem_lock);
}

static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
                          bool tx)
{
        struct device *cdev = cinfo->dev;
        unsigned long cap_id = ULONG_MAX;
        struct scmi_smc *scmi_info;
        struct resource res = {};
        u32 func_id;
        int ret;

        if (!tx)
                return -ENODEV;

        scmi_info = devm_kzalloc(dev, sizeof(*scmi_info), GFP_KERNEL);
        if (!scmi_info)
                return -ENOMEM;

        scmi_info->shmem = core->shmem->setup_iomap(cinfo, dev, tx, &res,
                                                    &scmi_info->io_ops);
        if (IS_ERR(scmi_info->shmem))
                return PTR_ERR(scmi_info->shmem);

        ret = of_property_read_u32(dev->of_node, "arm,smc-id", &func_id);
        if (ret < 0)
                return ret;

        if (of_device_is_compatible(dev->of_node, "qcom,scmi-smc")) {
                resource_size_t size = resource_size(&res);
                void __iomem *ptr = (void __iomem *)scmi_info->shmem + size - 8;
                /* The capability-id is kept in last 8 bytes of shmem.
                 *     +-------+ <-- 0
                 *     | shmem |
                 *     +-------+ <-- size - 8
                 *     | capId |
                 *     +-------+ <-- size
                 */
                memcpy_fromio(&cap_id, ptr, sizeof(cap_id));
        }

        if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param")) {
                scmi_info->param_page = SHMEM_PAGE(res.start);
                scmi_info->param_offset = SHMEM_OFFSET(res.start);
        }
        /*
         * If there is an interrupt named "a2p", then the service and
         * completion of a message is signaled by an interrupt rather than by
         * the return of the SMC call.
         */
        scmi_info->irq = of_irq_get_byname(cdev->of_node, "a2p");
        if (scmi_info->irq > 0) {
                ret = request_irq(scmi_info->irq, smc_msg_done_isr,
                                  IRQF_NO_SUSPEND, dev_name(dev), scmi_info);
                if (ret) {
                        dev_err(dev, "failed to setup SCMI smc irq\n");
                        return ret;
                }
        } else {
                cinfo->no_completion_irq = true;
        }

        scmi_info->func_id = func_id;
        scmi_info->cap_id = cap_id;
        scmi_info->cinfo = cinfo;
        smc_channel_lock_init(scmi_info);
        cinfo->transport_info = scmi_info;

        return 0;
}

static int smc_chan_free(int id, void *p, void *data)
{
        struct scmi_chan_info *cinfo = p;
        struct scmi_smc *scmi_info = cinfo->transport_info;

        /*
         * Different protocols might share the same chan info, so a previous
         * smc_chan_free call might have already freed the structure.
         */
        if (!scmi_info)
                return 0;

        /* Ignore any possible further reception on the IRQ path */
        if (scmi_info->irq > 0)
                free_irq(scmi_info->irq, scmi_info);

        cinfo->transport_info = NULL;
        scmi_info->cinfo = NULL;

        return 0;
}

static int smc_send_message(struct scmi_chan_info *cinfo,
                            struct scmi_xfer *xfer)
{
        struct scmi_smc *scmi_info = cinfo->transport_info;
        struct arm_smccc_res res;

        /*
         * Channel will be released only once response has been
         * surely fully retrieved, so after .mark_txdone()
         */
        smc_channel_lock_acquire(scmi_info, xfer);

        core->shmem->tx_prepare(scmi_info->shmem, xfer, cinfo,
                                scmi_info->io_ops->toio);

        if (scmi_info->cap_id != ULONG_MAX)
                arm_smccc_1_1_invoke(scmi_info->func_id, scmi_info->cap_id, 0,
                                     0, 0, 0, 0, 0, &res);
        else
                arm_smccc_1_1_invoke(scmi_info->func_id, scmi_info->param_page,
                                     scmi_info->param_offset, 0, 0, 0, 0, 0,
                                     &res);

        /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
        if (res.a0) {
                smc_channel_lock_release(scmi_info);
                return -EOPNOTSUPP;
        }

        return 0;
}

static void smc_fetch_response(struct scmi_chan_info *cinfo,
                               struct scmi_xfer *xfer)
{
        struct scmi_smc *scmi_info = cinfo->transport_info;

        core->shmem->fetch_response(scmi_info->shmem, xfer,
                                    scmi_info->io_ops->fromio);
}

static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret,
                            struct scmi_xfer *__unused)
{
        struct scmi_smc *scmi_info = cinfo->transport_info;

        smc_channel_lock_release(scmi_info);
}

static const struct scmi_transport_ops scmi_smc_ops = {
        .chan_available = smc_chan_available,
        .chan_setup = smc_chan_setup,
        .chan_free = smc_chan_free,
        .send_message = smc_send_message,
        .mark_txdone = smc_mark_txdone,
        .fetch_response = smc_fetch_response,
};

static struct scmi_desc scmi_smc_desc = {
        .ops = &scmi_smc_ops,
        .max_rx_timeout_ms = 30,
        .max_msg = 20,
        .max_msg_size = SCMI_SHMEM_MAX_PAYLOAD_SIZE,
        /*
         * Setting .sync_cmds_atomic_replies to true for SMC assumes that,
         * once the SMC instruction has completed successfully, the issued
         * SCMI command would have been already fully processed by the SCMI
         * platform firmware and so any possible response value expected
         * for the issued command will be immmediately ready to be fetched
         * from the shared memory area.
         */
        .sync_cmds_completed_on_ret = true,
        .atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE),
};

static const struct of_device_id scmi_of_match[] = {
        { .compatible = "arm,scmi-smc" },
        { .compatible = "arm,scmi-smc-param" },
        { .compatible = "qcom,scmi-smc" },
        { /* Sentinel */ },
};
MODULE_DEVICE_TABLE(of, scmi_of_match);

DEFINE_SCMI_TRANSPORT_DRIVER(scmi_smc, scmi_smc_driver, scmi_smc_desc,
                             scmi_of_match, core);
module_platform_driver(scmi_smc_driver);

MODULE_AUTHOR("Peng Fan <peng.fan@nxp.com>");
MODULE_AUTHOR("Nikunj Kela <quic_nkela@quicinc.com>");
MODULE_DESCRIPTION("SCMI SMC Transport driver");
MODULE_LICENSE("GPL");