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[PATCH 4.4 15/15] mmc: core: fix multi-bit bus width without high-speed mode

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

------------------

From: Anssi Hannula <anssi.hannula@bitwise.fi>

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>
---

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(-)

--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1581,10 +1581,10 @@ static int mmc_init_card(struct mmc_host
 		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;

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[PATCH 4.4 00/15] 4.4.51-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 11/15] printk: use rcuidle console tracepoint Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 09/15] futex: Move futex_init() to core_initcall Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 06/15] Input: elan_i2c - add ELAN0605 to the ACPI table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 12/15] NTB: ntb_transport: fix debugfs_remove_recursive Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 10/15] ARM: 8658/1: uaccess: fix zeroing of 64-bit get_user() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.4 02/15] [media] siano: make it work again with CONFIG_VMAP_STACK Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
    Re: [PATCH 4.4 02/15] [media] siano: make it work again with  CONFIG_VMAP_STACK Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-02-22 22:40 +0100
    Re: [PATCH 4.4 02/15] [media] siano: make it work again with  CONFIG_VMAP_STACK Eddie Chapman <eddie@ehuk.net> - 2017-02-22 22:50 +0100
  [PATCH 4.4 05/15] Fix missing sanity check in /dev/sg Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 04/15] scsi: dont BUG_ON() empty DMA transfers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 03/15] fuse: fix use after free issue in fuse_dev_do_read() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 14/15] bcache: Make gc wakeup sane, remove set_task_state() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 15/15] mmc: core: fix multi-bit bus width without high-speed mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 13/15] ntb_transport: Pick an unused queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  [PATCH 4.4 08/15] drm/dp/mst: fix kernel oops when turning off secondary monitor Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  Re: [PATCH 4.4 00/15] 4.4.51-stable review Guenter Roeck <linux@roeck-us.net> - 2017-02-21 17:20 +0100
  Re: [PATCH 4.4 00/15] 4.4.51-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-02-22 00:50 +0100

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