[PATCH 5.10 01/73] mmc: mmci: stm32: use a buffer for unaligned DMA requests

Sasha Levin
2024-03-13T16:46:44Z

From: Yann Gautier <yann.gautier@foss.st.com>

[ Upstream commit 970dc9c11a17994ab878016b536612ab00d1441d ]

In SDIO mode, the sg list for requests can be unaligned with what the
STM32 SDMMC internal DMA can support. In that case, instead of failing,
use a temporary bounce buffer to copy from/to the sg list.
This buffer is limited to 1MB. But for that we need to also limit
max_req_size to 1MB. It has not shown any throughput penalties for
SD-cards or eMMC.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Link: https://lore.kernel.org/r/20220328145114.334577-1-yann.gautier@foss.st.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Stable-dep-of: 6b1ba3f9040b ("mmc: mmci: stm32: fix DMA API overlapping mappings warning")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/mmc/host/mmci_stm32_sdmmc.c | 88 +++++++++++++++++++++++------
1 file changed, 71 insertions(+), 17 deletions(-)

diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
index 4cceb9bab0361..11ae0cb479239 100644
--- a/drivers/mmc/host/mmci_stm32_sdmmc.c
+++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
@@ -43,6 +43,9 @@ struct sdmmc_lli_desc {
struct sdmmc_idma {
dma_addr_t sg_dma;
void *sg_cpu;
+ dma_addr_t bounce_dma_addr;
+ void *bounce_buf;
+ bool use_bounce_buffer;
};

struct sdmmc_dlyb {
@@ -54,6 +57,8 @@ struct sdmmc_dlyb {
static int sdmmc_idma_validate_data(struct mmci_host *host,
struct mmc_data *data)
{
+ struct sdmmc_idma *idma = host->dma_priv;
+ struct device *dev = mmc_dev(host->mmc);
struct scatterlist *sg;
int i;

@@ -61,41 +66,69 @@ static int sdmmc_idma_validate_data(struct mmci_host *host,
* idma has constraints on idmabase & idmasize for each element
* excepted the last element which has no constraint on idmasize
*/
+ idma->use_bounce_buffer = false;
for_each_sg(data->sg, sg, data->sg_len - 1, i) {
if (!IS_ALIGNED(sg->offset, sizeof(u32)) ||
!IS_ALIGNED(sg->length, SDMMC_IDMA_BURST)) {
- dev_err(mmc_dev(host->mmc),
+ dev_dbg(mmc_dev(host->mmc),
"unaligned scatterlist: ofst:%x length:%d\n",
data->sg->offset, data->sg->length);
- return -EINVAL;
+ goto use_bounce_buffer;
}
}

if (!IS_ALIGNED(sg->offset, sizeof(u32))) {
- dev_err(mmc_dev(host->mmc),
+ dev_dbg(mmc_dev(host->mmc),
"unaligned last scatterlist: ofst:%x length:%d\n",
data->sg->offset, data->sg->length);
- return -EINVAL;
+ goto use_bounce_buffer;
}

+ return 0;
+
+use_bounce_buffer:
+ if (!idma->bounce_buf) {
+ idma->bounce_buf = dmam_alloc_coherent(dev,
+ host->mmc->max_req_size,
+ &idma->bounce_dma_addr,
+ GFP_KERNEL);
+ if (!idma->bounce_buf) {
+ dev_err(dev, "Unable to map allocate DMA bounce buffer.\n");
+ return -ENOMEM;
+ }
+ }
+
+ idma->use_bounce_buffer = true;
+
return 0;
}

static int _sdmmc_idma_prep_data(struct mmci_host *host,
struct mmc_data *data)
{
- int n_elem;
+ struct sdmmc_idma *idma = host->dma_priv;

- n_elem = dma_map_sg(mmc_dev(host->mmc),
- data->sg,
- data->sg_len,
- mmc_get_dma_dir(data));
+ if (idma->use_bounce_buffer) {
+ if (data->flags & MMC_DATA_WRITE) {
+ unsigned int xfer_bytes = data->blksz * data->blocks;

- if (!n_elem) {
- dev_err(mmc_dev(host->mmc), "dma_map_sg failed\n");
- return -EINVAL;
- }
+ sg_copy_to_buffer(data->sg, data->sg_len,
+ idma->bounce_buf, xfer_bytes);
+ dma_wmb();
+ }
+ } else {
+ int n_elem;
+
+ n_elem = dma_map_sg(mmc_dev(host->mmc),
+ data->sg,
+ data->sg_len,
+ mmc_get_dma_dir(data));

+ if (!n_elem) {
+ dev_err(mmc_dev(host->mmc), "dma_map_sg failed\n");
+ return -EINVAL;
+ }
+ }
return 0;
}

@@ -112,8 +145,19 @@ static int sdmmc_idma_prep_data(struct mmci_host *host,
static void sdmmc_idma_unprep_data(struct mmci_host *host,
struct mmc_data *data, int err)
{
- dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
- mmc_get_dma_dir(data));
+ struct sdmmc_idma *idma = host->dma_priv;
+
+ if (idma->use_bounce_buffer) {
+ if (data->flags & MMC_DATA_READ) {
+ unsigned int xfer_bytes = data->blksz * data->blocks;
+
+ sg_copy_from_buffer(data->sg, data->sg_len,
+ idma->bounce_buf, xfer_bytes);
+ }
+ } else {
+ dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
+ mmc_get_dma_dir(data));
+ }
}

static int sdmmc_idma_setup(struct mmci_host *host)
@@ -137,6 +181,8 @@ static int sdmmc_idma_setup(struct mmci_host *host)
host->mmc->max_segs = SDMMC_LLI_BUF_LEN /
sizeof(struct sdmmc_lli_desc);
host->mmc->max_seg_size = host->variant->stm32_idmabsize_mask;
+
+ host->mmc->max_req_size = SZ_1M;
} else {
host->mmc->max_segs = 1;
host->mmc->max_seg_size = host->mmc->max_req_size;
@@ -154,8 +200,16 @@ static int sdmmc_idma_start(struct mmci_host *host, unsigned int *datactrl)
struct scatterlist *sg;
int i;

- if (!host->variant->dma_lli || data->sg_len == 1) {
- writel_relaxed(sg_dma_address(data->sg),
+ if (!host->variant->dma_lli || data->sg_len == 1 ||
+ idma->use_bounce_buffer) {
+ u32 dma_addr;
+
+ if (idma->use_bounce_buffer)
+ dma_addr = idma->bounce_dma_addr;
+ else
+ dma_addr = sg_dma_address(data->sg);
+
+ writel_relaxed(dma_addr,
host->base + MMCI_STM32_IDMABASE0R);
writel_relaxed(MMCI_STM32_IDMAEN,
host->base + MMCI_STM32_IDMACTRLR);
--
2.43.0