On Mon, 28 Mar 2022 at 16:51, Yann Gautier <yann.gautier@xxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxx>
Queued up for v5.19 on the devel branch, thanks!
Kind regards
Uffe
> ---
> Changes since v1:
> - allocate bounce buffer in sdmmc_idma_validate_data()
> - realign on top of mmc/devel branch
> (25e14a52d35928a1831ca98889a8a25ac3017990)
>
> 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 4566d7fc9055..60bca78a72b1 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);
> --
> 2.25.1
>
