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

Commit 577fb13199 ("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: 577fb13199 ("mmc: rework selection of bus speed mode")
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Anssi Hannula 2017-02-13 13:46:41 +02:00 committed by Ulf Hansson
parent 7089db84e3
commit 3d4ef32975
1 changed files with 2 additions and 2 deletions
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4
drivers/mmc/core/mmc.c
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@ -1706,10 +1706,10 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
err = mmc_select_hs400(card); err = mmc_select_hs400(card);
if (err) if (err)
goto free_card; goto free_card;
} else if (mmc_card_hs(card)) { } else {
/* Select the desired bus width optionally */ /* Select the desired bus width optionally */
err = mmc_select_bus_width(card); err = mmc_select_bus_width(card);
if (err > 0) { if (err > 0 && mmc_card_hs(card)) {
err = mmc_select_hs_ddr(card); err = mmc_select_hs_ddr(card);
if (err) if (err)
goto free_card; goto free_card;