On 17/02/21 7:22 am, DooHyun Hwang wrote:
> This makes to handle read errors faster by not retrying
> multiple block read(CMD18) errors with single block reads(CMD17).
>
> On some bad SD Cards that have problem with read operations,
> it is not helpful to retry multiple block read errors with
> several single block reads, and it is delayed to treat read
> operations as I/O error as much as retrying single block reads.
If the issue is that it takes too long, then maybe it would be better to get
mmc_blk_read_single() to give up after a certain amount of time.
>
> Signed-off-by: DooHyun Hwang <dh0421.hwang@xxxxxxxxxxx>
> ---
> drivers/mmc/core/block.c | 3 ++-
> drivers/mmc/core/host.c | 6 ++++++
> include/linux/mmc/host.h | 3 +++
> 3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index d666e24fbe0e..e25aaf8fca34 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -1809,7 +1809,8 @@ static void mmc_blk_mq_rw_recovery(struct mmc_queue *mq, struct request *req)
>
> /* FIXME: Missing single sector read for large sector size */
> if (!mmc_large_sector(card) && rq_data_dir(req) == READ &&
> - brq->data.blocks > 1) {
> + brq->data.blocks > 1 &&
> + !card->host->no_single_read_retry) {
> /* Read one sector at a time */
> mmc_blk_read_single(mq, req);
> return;
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 9b89a91b6b47..3bf5b2fc111b 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -352,6 +352,12 @@ int mmc_of_parse(struct mmc_host *host)
> if (device_property_read_bool(dev, "no-mmc"))
> host->caps2 |= MMC_CAP2_NO_MMC;
>
> + if (device_property_read_bool(dev, "no-single-read-retry")) {
> + dev_info(host->parent,
> + "Single block read retrying is not supported\n");
> + host->no_single_read_retry = true;
> + }
> +
> /* Must be after "non-removable" check */
> if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
> if (host->caps & MMC_CAP_NONREMOVABLE)
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 26a3c7bc29ae..faec55035a63 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -502,6 +502,9 @@ struct mmc_host {
> /* Host Software Queue support */
> bool hsq_enabled;
>
> + /* Do not retry multi block read as single block read */
> + bool no_single_read_retry;
> +
> unsigned long private[] ____cacheline_aligned;
> };
>
>
