linux-kernel - [PATCH 3.12 65/78] mmc: Allow forward compatibility for eMMC

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Message-Id: <6f6abe510fc7cb0f6933c1b99ab059b1899e9cdb.1461323133.git.jslaby@suse.cz>
Date:	Fri, 22 Apr 2016 13:05:48 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Romain Izard <romain.izard.pro@...il.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 65/78] mmc: Allow forward compatibility for eMMC

From: Romain Izard <romain.izard.pro@...il.com>

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

===============

commit 03a59437ef6b6ad7fb0165cb9b96c08d6bf057fc upstream.

As stated by the eMMC 5.0 specification, a chip should not be rejected
only because of the revision stated in the EXT_CSD_REV field of the
EXT_CSD register.

Remove the control on this value, the control of the CSD_STRUCTURE field
should be sufficient to reject future incompatible changes.

Signed-off-by: Romain Izard <romain.izard.pro@...il.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/mmc/core/mmc.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 6d02012a1d0b..36d6701de972 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -292,13 +292,12 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 		}
 	}
 
+	/*
+	 * The EXT_CSD format is meant to be forward compatible. As long
+	 * as CSD_STRUCTURE does not change, all values for EXT_CSD_REV
+	 * are authorized, see JEDEC JESD84-B50 section B.8.
+	 */
 	card->ext_csd.rev = ext_csd[EXT_CSD_REV];
-	if (card->ext_csd.rev > 7) {
-		pr_err("%s: unrecognised EXT_CSD revision %d\n",
-			mmc_hostname(card->host), card->ext_csd.rev);
-		err = -EINVAL;
-		goto out;
-	}
 
 	card->ext_csd.raw_sectors[0] = ext_csd[EXT_CSD_SEC_CNT + 0];
 	card->ext_csd.raw_sectors[1] = ext_csd[EXT_CSD_SEC_CNT + 1];
-- 
2.8.1