Due to hardware bugs, some MMC host controllers don't support multiple-block reads[1]. To resolve, add a new MMC capability flag, MMC_CAP_NO_MULTI_READ, which can be set by affected host controller drivers. When this capability is set, all reads will be issued one sector at a time.
1. See for example Advisory 2.1.1.128 "MMC: Multiple Block Read Operation Issue" in _OMAP3530/3525/3515/3503 Silicon Errata_ Revision F (October 2010) (SPRZ278F), available from http://focus.ti.com/lit/er/sprz278f/sprz278f.pdf Signed-off-by: Paul Walmsley <p...@pwsan.com> Cc: Dave Hylands <dhyla...@gmail.com> Cc: Steve Sakoman <sako...@gmail.com> Cc: Chris Ball <c...@laptop.org> --- drivers/mmc/card/block.c | 21 ++++++++++++++------- include/linux/mmc/host.h | 1 + 2 files changed, 15 insertions(+), 7 deletions(-) diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c index 1ff5486..927f9d5 100644 --- a/drivers/mmc/card/block.c +++ b/drivers/mmc/card/block.c @@ -954,13 +954,20 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq, if (brq->data.blocks > card->host->max_blk_count) brq->data.blocks = card->host->max_blk_count; - /* - * After a read error, we redo the request one sector at a time - * in order to accurately determine which sectors can be read - * successfully. - */ - if (disable_multi && brq->data.blocks > 1) - brq->data.blocks = 1; + if (brq->data.blocks > 1) { + /* + * After a read error, we redo the request one sector + * at a time in order to accurately determine which + * sectors can be read successfully. + */ + if (disable_multi) + brq->data.blocks = 1; + + /* Some controllers can't do multiblock reads due to hw bugs */ + if (card->host->caps & MMC_CAP_NO_MULTI_READ && + rq_data_dir(req) == READ) + brq->data.blocks = 1; + } if (brq->data.blocks > 1 || do_rel_wr) { /* SPI multiblock writes terminate using a special diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index 1d09562..745f506 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -229,6 +229,7 @@ struct mmc_host { #define MMC_CAP_MAX_CURRENT_600 (1 << 28) /* Host max current limit is 600mA */ #define MMC_CAP_MAX_CURRENT_800 (1 << 29) /* Host max current limit is 800mA */ #define MMC_CAP_CMD23 (1 << 30) /* CMD23 supported. */ +#define MMC_CAP_NO_MULTI_READ (1 << 31) /* Multiblock reads don't work */ mmc_pm_flag_t pm_caps; /* supported pm features */ -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
