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 78187699467a11cb6ad43b9fb2298aaeee933a13..79a0c26e14190077d707f9e0141ca230e6d13d2d 100644 (file)
--- 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;