linux-kernel - [PATCH 4.18 128/135] mmc: block: avoid multiblock reads for the last sector in SPI mode

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Date:   Tue, 16 Oct 2018 19:05:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chris Boot <bootc@...tc.net>,
        Clément Péron <peron.clem@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 4.18 128/135] mmc: block: avoid multiblock reads for the last sector in SPI mode

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Boot <bootc@...tc.net>

commit 41591b38f5f8f78344954b68582b5f00e56ffe61 upstream.

On some SD cards over SPI, reading with the multiblock read command the last
sector will leave the card in a bad state.

Remove last sectors from the multiblock reading cmd.

Signed-off-by: Chris Boot <bootc@...tc.net>
Signed-off-by: Clément Péron <peron.clem@...il.com>
Cc: stable@...r.kernel.org # v4.10+
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/core/block.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1371,6 +1371,16 @@ static void mmc_blk_data_prep(struct mmc
 
 	if (brq->data.blocks > 1) {
 		/*
+		 * Some SD cards in SPI mode return a CRC error or even lock up
+		 * completely when trying to read the last block using a
+		 * multiblock read command.
+		 */
+		if (mmc_host_is_spi(card->host) && (rq_data_dir(req) == READ) &&
+		    (blk_rq_pos(req) + blk_rq_sectors(req) ==
+		     get_capacity(md->disk)))
+			brq->data.blocks--;
+
+		/*
 		 * After a read error, we redo the request one sector
 		 * at a time in order to accurately determine which
 		 * sectors can be read successfully.