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mmc: core: add workaround for controllers with broken multiblock reads 

Due to hardware bugs, some MMC host controllers don't support
multiple-block reads[1].  To resolve, add a new MMC capability flag,
MMC_CAP2_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 <paul@pwsan.com>
Cc: Dave Hylands <dhylands@gmail.com>
Tested-by: Steve Sakoman <sakoman@gmail.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Paul Walmsley 2011-10-06 14:50:33 -06:00 committed by Chris Ball
parent b6ad726e3f
commit 2bf22b3982
2 changed files with 15 additions and 7 deletions
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21
drivers/mmc/card/block.c
View File

@ -1030,13 +1030,20 @@ 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->caps2 & MMC_CAP2_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

1
include/linux/mmc/host.h
View File

@ -241,6 +241,7 @@ struct mmc_host {
#define MMC_CAP2_BOOTPART_NOACC (1 << 0) /* Boot partition no access */
#define MMC_CAP2_CACHE_CTRL (1 << 1) /* Allow cache control */
#define MMC_CAP2_POWEROFF_NOTIFY (1 << 2) /* Notify poweroff supported */
#define MMC_CAP2_NO_MULTI_READ (1 << 3) /* Multiblock reads don't work */
mmc_pm_flag_t pm_caps; /* supported pm features */
unsigned int power_notify_type;