FAILED: patch "[PATCH] mmc: core: fix multi-bit bus width without high-speed mode" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Anssi Hannula <[email protected]>
Date: Mon, 13 Feb 2017 13:46:41 +0200
Subject: [PATCH] mmc: core: fix multi-bit bus width without high-speed mode

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.

index b61b52f9da3d..0fccca075e29 100644
@@ -1706,10 +1706,10 @@ 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 (err > 0) {
+		if (err > 0 && mmc_card_hs(card)) {
 			err = mmc_select_hs_ddr(card);
 			if (err)
 				goto free_card;

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.

[[email protected]: backported for the different err variable
check on v4.4 and tested]
---

Here is a trivial backport as the upstream commit did not apply cleanly to 4.4-stable.

 drivers/mmc/core/mmc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 7818769..79a0c26 100644
@@ -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;

2.8.3