From: Anssi Hannula <anssi.hannula@bitwise.fi>
Date: Mon, 13 Feb 2017 11:46:41 +0000 (+0200)
Subject: mmc: core: fix multi-bit bus width without high-speed mode
X-Git-Tag: v4.4.51~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5a86b1150f6ce88c43d669bfe14c96b312a1cceb;p=profile%2Fcommon%2Fplatform%2Fkernel%2Flinux-artik7.git

mmc: core: fix multi-bit bus width without high-speed mode

commit 3d4ef329757cfd5e0b23cce97cdeca7e2df89c99 upstream.

Commit 577fb13199b1 ("mmc: rework selection of bus speed mode")
refactored bus width selection code to mmc_select_bus_width().

However, it also altered the behavior to not call the selection code in
non-high-speed modes anymore.

This causes 1-bit mode to always be used when the high-speed mode is not
enabled, even though 4-bit and 8-bit bus are valid bus widths in the
backwards-compatibility (legacy) mode as well (see e.g. 5.3.2 Bus Speed
Modes in JEDEC 84-B50). This results in a significant regression in
transfer speeds.

Fix the code to allow 4-bit and 8-bit widths even without high-speed
mode, as before.

Tested with a Zynq-7000 PicoZed 7020 board.

Fixes: 577fb13199b1 ("mmc: rework selection of bus speed mode")
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[anssi.hannula@bitwise.fi: backported for the different err variable
 check on v4.4 and tested]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 7818769..79a0c26 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1581,10 +1581,10 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		err = mmc_select_hs400(card);
 		if (err)
 			goto free_card;
-	} else if (mmc_card_hs(card)) {
+	} else {
 		/* Select the desired bus width optionally */
 		err = mmc_select_bus_width(card);
-		if (!IS_ERR_VALUE(err)) {
+		if (!IS_ERR_VALUE(err) && mmc_card_hs(card)) {
 			err = mmc_select_hs_ddr(card);
 			if (err)
 				goto free_card;