// SPDX-License-Identifier: GPL-2.0
/*
 * An example software sink buffer for Intel TH MSU.
 *
 * Copyright (C) 2019 Intel Corporation.
 */

#include <linux/intel_th.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>

#define MAX_SGTS 16

struct msu_sink_private {
        struct device   *dev;
        struct sg_table **sgts;
        unsigned int    nr_sgts;
};

static void *msu_sink_assign(struct device *dev, int *mode)
{
        struct msu_sink_private *priv;

        priv = kzalloc_obj(*priv);
        if (!priv)
                return NULL;

        priv->sgts = kcalloc(MAX_SGTS, sizeof(void *), GFP_KERNEL);
        if (!priv->sgts) {
                kfree(priv);
                return NULL;
        }

        priv->dev = dev;
        *mode = MSC_MODE_MULTI;

        return priv;
}

static void msu_sink_unassign(void *data)
{
        struct msu_sink_private *priv = data;

        kfree(priv->sgts);
        kfree(priv);
}

/* See also: msc.c: __msc_buffer_win_alloc() */
static int msu_sink_alloc_window(void *data, struct sg_table **sgt, size_t size)
{
        struct msu_sink_private *priv = data;
        unsigned int nents;
        struct scatterlist *sg_ptr;
        void *block;
        int ret, i;

        if (priv->nr_sgts == MAX_SGTS)
                return -ENOMEM;

        nents = DIV_ROUND_UP(size, PAGE_SIZE);

        ret = sg_alloc_table(*sgt, nents, GFP_KERNEL);
        if (ret)
                return -ENOMEM;

        priv->sgts[priv->nr_sgts++] = *sgt;

        for_each_sg((*sgt)->sgl, sg_ptr, nents, i) {
                block = dma_alloc_coherent(priv->dev->parent->parent,
                                           PAGE_SIZE, &sg_dma_address(sg_ptr),
                                           GFP_KERNEL);
                if (!block)
                        return -ENOMEM;

                sg_set_buf(sg_ptr, block, PAGE_SIZE);
        }

        return nents;
}

/* See also: msc.c: __msc_buffer_win_free() */
static void msu_sink_free_window(void *data, struct sg_table *sgt)
{
        struct msu_sink_private *priv = data;
        struct scatterlist *sg_ptr;
        int i;

        for_each_sg(sgt->sgl, sg_ptr, sgt->nents, i) {
                dma_free_coherent(priv->dev->parent->parent, PAGE_SIZE,
                                  sg_virt(sg_ptr), sg_dma_address(sg_ptr));
        }

        sg_free_table(sgt);
        priv->nr_sgts--;
}

static int msu_sink_ready(void *data, struct sg_table *sgt, size_t bytes)
{
        struct msu_sink_private *priv = data;

        intel_th_msc_window_unlock(priv->dev, sgt);

        return 0;
}

static const struct msu_buffer sink_mbuf = {
        .name           = "sink",
        .assign         = msu_sink_assign,
        .unassign       = msu_sink_unassign,
        .alloc_window   = msu_sink_alloc_window,
        .free_window    = msu_sink_free_window,
        .ready          = msu_sink_ready,
};

module_intel_th_msu_buffer(sink_mbuf);

MODULE_DESCRIPTION("example software sink buffer for Intel TH MSU");
MODULE_LICENSE("GPL v2");