[PATCH 5/5] mmc: meson-gx: switch to descriptor chain mode

Heiner Kallweit
2017-03-15T19:35:04Z

Switch the driver from using a linearized bounce buffer to descriptor
chain mode. This drastically improves performance.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
drivers/mmc/host/meson-gx-mmc.c | 207 ++++++++++++++++++++++------------------
1 file changed, 116 insertions(+), 91 deletions(-)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 425060da..d561065b 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -121,6 +121,13 @@
#define SD_EMMC_CFG_CMD_GAP 16 /* in clock cycles */
#define MUX_CLK_NUM_PARENTS 2

+struct sd_emmc_desc {
+ u32 cmd_cfg;
+ u32 cmd_arg;
+ u32 cmd_data;
+ u32 cmd_resp;
+};
+
struct meson_host {
struct device *dev;
struct mmc_host *mmc;
@@ -136,19 +143,12 @@ struct meson_host {
struct clk_divider cfg_div;
struct clk *cfg_div_clk;

- unsigned int bounce_buf_size;
- void *bounce_buf;
- dma_addr_t bounce_dma_addr;
+ struct sd_emmc_desc *descs;
+ dma_addr_t descs_dma_addr;

bool vqmmc_enabled;
};

-struct sd_emmc_desc {
- u32 cmd_cfg;
- u32 cmd_arg;
- u32 cmd_data;
- u32 cmd_resp;
-};
#define CMD_CFG_LENGTH_SHIFT 0
#define CMD_CFG_LENGTH_MASK 0x1ff
#define CMD_CFG_BLOCK_MODE BIT(9)
@@ -185,6 +185,36 @@ static struct mmc_command *meson_mmc_get_next_command(struct mmc_command *cmd)
return NULL;
}

+static enum dma_data_direction meson_mmc_get_data_dir(struct mmc_data *data)
+{
+ return data->flags & MMC_DATA_WRITE ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+}
+
+static void meson_mmc_pre_req(struct mmc_host *mmc, struct mmc_request *mrq)
+{
+ struct mmc_data *data = mrq->data;
+
+ if (!data)
+ return;
+
+ data->host_cookie = true;
+
+ data->sg_count = dma_map_sg(mmc_dev(mmc), data->sg, data->sg_len,
+ meson_mmc_get_data_dir(data));
+ if (!data->sg_count)
+ dev_err(mmc_dev(mmc), "dma_map_sg failed");
+}
+
+static void meson_mmc_post_req(struct mmc_host *mmc, struct mmc_request *mrq,
+ int err)
+{
+ struct mmc_data *data = mrq->data;
+
+ if (data && data->sg_count)
+ dma_unmap_sg(mmc_dev(mmc), data->sg, data->sg_len,
+ meson_mmc_get_data_dir(data));
+}
+
static int meson_mmc_clk_set(struct meson_host *host, unsigned long clk_rate)
{
struct mmc_host *mmc = host->mmc;
@@ -434,94 +464,91 @@ static void meson_mmc_request_done(struct mmc_host *mmc,
static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
{
struct meson_host *host = mmc_priv(mmc);
- struct sd_emmc_desc *desc, desc_tmp;
- u32 cfg;
- u8 blk_len, cmd_cfg_timeout;
- unsigned int xfer_bytes = 0;
-
- /* Setup descriptors */
- dma_rmb();
- desc = &desc_tmp;
- memset(desc, 0, sizeof(struct sd_emmc_desc));
+ struct sd_emmc_desc *desc = host->descs;
+ struct mmc_data *data;
+ struct scatterlist *sg;
+ u32 cfg, cmd_cfg = 0;
+ u8 blk_len;
+ int i;

- desc->cmd_cfg |= (cmd->opcode & CMD_CFG_CMD_INDEX_MASK) <<
- CMD_CFG_CMD_INDEX_SHIFT;
- desc->cmd_cfg |= CMD_CFG_OWNER; /* owned by CPU */
- desc->cmd_arg = cmd->arg;
+ cmd_cfg |= (cmd->opcode & CMD_CFG_CMD_INDEX_MASK) <<
+ CMD_CFG_CMD_INDEX_SHIFT;
+ cmd_cfg |= CMD_CFG_OWNER; /* owned by CPU */

/* Response */
if (cmd->flags & MMC_RSP_PRESENT) {
- desc->cmd_cfg &= ~CMD_CFG_NO_RESP;
+ cmd_cfg &= ~CMD_CFG_NO_RESP;
if (cmd->flags & MMC_RSP_136)
- desc->cmd_cfg |= CMD_CFG_RESP_128;
- desc->cmd_cfg |= CMD_CFG_RESP_NUM;
- desc->cmd_resp = 0;
+ cmd_cfg |= CMD_CFG_RESP_128;
+ cmd_cfg |= CMD_CFG_RESP_NUM;

if (!(cmd->flags & MMC_RSP_CRC))
- desc->cmd_cfg |= CMD_CFG_RESP_NOCRC;
+ cmd_cfg |= CMD_CFG_RESP_NOCRC;

if (cmd->flags & MMC_RSP_BUSY)
- desc->cmd_cfg |= CMD_CFG_R1B;
+ cmd_cfg |= CMD_CFG_R1B;
} else {
- desc->cmd_cfg |= CMD_CFG_NO_RESP;
+ cmd_cfg |= CMD_CFG_NO_RESP;
}

- /* data? */
- if (cmd->data) {
- desc->cmd_cfg |= CMD_CFG_DATA_IO | CMD_CFG_BLOCK_MODE;
- desc->cmd_cfg |= (cmd->data->blocks & CMD_CFG_LENGTH_MASK) <<
- CMD_CFG_LENGTH_SHIFT;
+ data = cmd->data;
+ if (data) {
+ data->bytes_xfered = 0;
+ cmd_cfg |= CMD_CFG_DATA_IO | CMD_CFG_BLOCK_MODE;
+ cmd_cfg |= ilog2(SD_EMMC_CMD_TIMEOUT_DATA) <<
+ CMD_CFG_TIMEOUT_SHIFT;
+
+ if (data->flags & MMC_DATA_WRITE)
+ cmd_cfg |= CMD_CFG_DATA_WR;

/* check if block-size matches, if not update */
cfg = readl(host->regs + SD_EMMC_CFG);
blk_len = cfg & (CFG_BLK_LEN_MASK << CFG_BLK_LEN_SHIFT);
blk_len >>= CFG_BLK_LEN_SHIFT;
- if (blk_len != ilog2(cmd->data->blksz)) {
+ if (blk_len != ilog2(data->blksz)) {
dev_dbg(host->dev, "%s: update blk_len %d -> %d\n",
- __func__, blk_len, ilog2(cmd->data->blksz));
- blk_len = ilog2(cmd->data->blksz);
+ __func__, blk_len, ilog2(data->blksz));
+ blk_len = ilog2(data->blksz);
cfg &= ~(CFG_BLK_LEN_MASK << CFG_BLK_LEN_SHIFT);
cfg |= blk_len << CFG_BLK_LEN_SHIFT;
writel(cfg, host->regs + SD_EMMC_CFG);
}

- cmd->data->bytes_xfered = 0;
- xfer_bytes = cmd->data->blksz * cmd->data->blocks;
- if (cmd->data->flags & MMC_DATA_WRITE) {
- desc->cmd_cfg |= CMD_CFG_DATA_WR;
- WARN_ON(xfer_bytes > host->bounce_buf_size);
- sg_copy_to_buffer(cmd->data->sg, cmd->data->sg_len,
- host->bounce_buf, xfer_bytes);
- cmd->data->bytes_xfered = xfer_bytes;
- dma_wmb();
- } else {
- desc->cmd_cfg &= ~CMD_CFG_DATA_WR;
+ for_each_sg(data->sg, sg, data->sg_len, i) {
+ desc[i].cmd_cfg = cmd_cfg;
+ sg_dma_len(sg) = sg->length;
+ desc[i].cmd_cfg |= (sg_dma_len(sg) / data->blksz)
+ << CMD_CFG_LENGTH_SHIFT;
+ if (i > 0)
+ desc[i].cmd_cfg |= CMD_CFG_NO_CMD;
+ desc[i].cmd_arg = cmd->arg;
+ desc[i].cmd_resp = 0;
+ desc[i].cmd_data = sg_dma_address(sg);
}
-
- desc->cmd_data = host->bounce_dma_addr & CMD_DATA_MASK;
-
- cmd_cfg_timeout = ilog2(SD_EMMC_CMD_TIMEOUT_DATA);
+ desc[data->sg_len - 1].cmd_cfg |= CMD_CFG_END_OF_CHAIN;
} else {
- desc->cmd_cfg &= ~CMD_CFG_DATA_IO;
- cmd_cfg_timeout = ilog2(SD_EMMC_CMD_TIMEOUT);
+ cmd_cfg |= ilog2(SD_EMMC_CMD_TIMEOUT) << CMD_CFG_TIMEOUT_SHIFT;
+ cmd_cfg |= CMD_CFG_END_OF_CHAIN;
+ desc[0].cmd_cfg = cmd_cfg;
+ desc[0].cmd_arg = cmd->arg;
+ desc[0].cmd_resp = 0;
+ desc[0].cmd_data = 0;
}
- desc->cmd_cfg |= (cmd_cfg_timeout & CMD_CFG_TIMEOUT_MASK) <<
- CMD_CFG_TIMEOUT_SHIFT;

host->cmd = cmd;

- /* Last descriptor */
- desc->cmd_cfg |= CMD_CFG_END_OF_CHAIN;
- writel(desc->cmd_cfg, host->regs + SD_EMMC_CMD_CFG);
- writel(desc->cmd_data, host->regs + SD_EMMC_CMD_DAT);
- writel(desc->cmd_resp, host->regs + SD_EMMC_CMD_RSP);
wmb(); /* ensure descriptor is written before kicked */
- writel(desc->cmd_arg, host->regs + SD_EMMC_CMD_ARG);
+ cfg = host->descs_dma_addr | START_DESC_BUSY;
+ writel(cfg, host->regs + SD_EMMC_START);
}

static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
{
struct meson_host *host = mmc_priv(mmc);
+ bool needs_pre_post_req = mrq->data && !mrq->data->host_cookie;
+
+ if (needs_pre_post_req)
+ meson_mmc_pre_req(mmc, mrq);

/* Stop execution */
writel(0, host->regs + SD_EMMC_START);
@@ -530,6 +557,9 @@ static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
meson_mmc_start_cmd(mmc, mrq->sbc);
else
meson_mmc_start_cmd(mmc, mrq->cmd);
+
+ if (needs_pre_post_req)
+ meson_mmc_post_req(mmc, mrq, 0);
}

static void meson_mmc_read_resp(struct mmc_host *mmc, struct mmc_command *cmd)
@@ -550,6 +580,7 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
{
struct meson_host *host = dev_id;
struct mmc_command *cmd;
+ struct mmc_data *data;
u32 irq_en, status, raw_status;
irqreturn_t ret = IRQ_HANDLED;

@@ -561,6 +592,8 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
if (WARN_ON(!cmd))
return IRQ_NONE;

+ data = cmd->data;
+
spin_lock(&host->lock);
irq_en = readl(host->regs + SD_EMMC_IRQ_EN);
raw_status = readl(host->regs + SD_EMMC_STATUS);
@@ -598,12 +631,17 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
dev_dbg(host->dev, "Unhandled IRQ: Descriptor timeout\n");
cmd->error = -ETIMEDOUT;
}
+
+ if (data && !cmd->error)
+ data->bytes_xfered = data->blksz * data->blocks;
+
if (status & IRQ_SDIO)
dev_dbg(host->dev, "Unhandled IRQ: SDIO.\n");

- if (status & (IRQ_END_OF_CHAIN | IRQ_RESP_STATUS))
- ret = IRQ_WAKE_THREAD;
- else {
+ if (status & (IRQ_END_OF_CHAIN | IRQ_RESP_STATUS)) {
+ if (meson_mmc_get_next_command(cmd))
+ ret = IRQ_WAKE_THREAD;
+ } else {
dev_warn(host->dev, "Unknown IRQ! status=0x%04x: MMC CMD%u arg=0x%08x flags=0x%08x stop=%d\n",
status, cmd->opcode, cmd->arg,
cmd->flags, cmd->mrq->stop ? 1 : 0);
@@ -632,26 +670,12 @@ static irqreturn_t meson_mmc_irq_thread(int irq, void *dev_id)
{
struct meson_host *host = dev_id;
struct mmc_command *next_cmd, *cmd = host->cmd;
- struct mmc_data *data;
- unsigned int xfer_bytes;

if (WARN_ON(!cmd))
return IRQ_NONE;

- data = cmd->data;
- if (data && data->flags & MMC_DATA_READ) {
- xfer_bytes = data->blksz * data->blocks;
- WARN_ON(xfer_bytes > host->bounce_buf_size);
- sg_copy_from_buffer(data->sg, data->sg_len,
- host->bounce_buf, xfer_bytes);
- data->bytes_xfered = xfer_bytes;
- }
-
next_cmd = meson_mmc_get_next_command(cmd);
- if (next_cmd)
- meson_mmc_start_cmd(host->mmc, next_cmd);
- else
- meson_mmc_request_done(host->mmc, cmd->mrq);
+ meson_mmc_start_cmd(host->mmc, next_cmd);

return IRQ_HANDLED;
}
@@ -685,6 +709,8 @@ static const struct mmc_host_ops meson_mmc_ops = {
.request = meson_mmc_request,
.set_ios = meson_mmc_set_ios,
.get_cd = meson_mmc_get_cd,
+ .pre_req = meson_mmc_pre_req,
+ .post_req = meson_mmc_post_req,
};

static int meson_mmc_probe(struct platform_device *pdev)
@@ -764,15 +790,14 @@ static int meson_mmc_probe(struct platform_device *pdev)

mmc->caps |= MMC_CAP_CMD23;
mmc->max_blk_count = CMD_CFG_LENGTH_MASK;
- mmc->max_req_size = mmc->max_blk_count * mmc->max_blk_size;
-
- /* data bounce buffer */
- host->bounce_buf_size = mmc->max_req_size;
- host->bounce_buf =
- dma_alloc_coherent(host->dev, host->bounce_buf_size,
- &host->bounce_dma_addr, GFP_KERNEL);
- if (host->bounce_buf == NULL) {
- dev_err(host->dev, "Unable to map allocate DMA bounce buffer.\n");
+ mmc->max_segs = PAGE_SIZE / sizeof(struct sd_emmc_desc);
+ mmc->max_seg_size = mmc->max_blk_count * mmc->max_blk_size;
+ mmc->max_req_size = mmc->max_seg_size * mmc->max_segs;
+
+ host->descs = dma_alloc_coherent(host->dev, PAGE_SIZE,
+ &host->descs_dma_addr, GFP_KERNEL);
+ if (!host->descs) {
+ dev_err(host->dev, "Allocating descriptor DMA buffer failed\n");
ret = -ENOMEM;
goto err_div_clk;
}
@@ -797,8 +822,8 @@ static int meson_mmc_remove(struct platform_device *pdev)
/* disable interrupts */
writel(0, host->regs + SD_EMMC_IRQ_EN);

- dma_free_coherent(host->dev, host->bounce_buf_size,
- host->bounce_buf, host->bounce_dma_addr);
+ dma_free_coherent(host->dev, PAGE_SIZE, host->descs,
+ host->descs_dma_addr);

clk_disable_unprepare(host->cfg_div_clk);
clk_disable_unprepare(host->core_clk);
--
2.12.0