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Commit 2bf22b39 authored by Paul Walmsley's avatar Paul Walmsley Committed by Chris Ball
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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: default avatarPaul Walmsley <paul@pwsan.com>
Cc: Dave Hylands <dhylands@gmail.com>
Tested-by: default avatarSteve Sakoman <sakoman@gmail.com>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent b6ad726e

drivers/mmc/card/block.c

+14 −7
Original line number Diff line number Diff line
@@ -1030,14 +1030,21 @@ 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;



	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.

		 * 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)

		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

		 * token, not a STOP_TRANSMISSION request.

include/linux/mmc/host.h

+1 −0
Original line number Diff line number Diff line
@@ -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;