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    Subject[PATCH 4.4 136/342] mmc: mmc: Fix incorrect use of driver strength switching HS200 and HS400
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Wenkai Du <wenkai.du@intel.com>

    commit adb24d42a516bca8b9741ed21206509daaab5b13 upstream.

    Commit cc4f414c885c ("mmc: mmc: Add driver strength selection")
    added driver strength selection for eMMC HS200 and HS400 modes.
    That patch also set the driver stength when transitioning through
    High Speed mode to HS200/HS400, but driver strength is not defined
    for High Speed mode. While the JEDEC specification is not clear
    on this point it has been observed to cause problems for some eMMC,
    and removing the driver strength setting in this case makes it
    consistent with the normal use of High Speed mode.

    Signed-off-by: Wenkai Du <wenkai.du@intel.com>
    Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
    Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/mmc/core/mmc.c | 6 ++----
    1 file changed, 2 insertions(+), 4 deletions(-)

    --- a/drivers/mmc/core/mmc.c
    +++ b/drivers/mmc/core/mmc.c
    @@ -1076,8 +1076,7 @@ static int mmc_select_hs400(struct mmc_c
    mmc_set_clock(host, max_dtr);

    /* Switch card to HS mode */
    - val = EXT_CSD_TIMING_HS |
    - card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
    + val = EXT_CSD_TIMING_HS;
    err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
    EXT_CSD_HS_TIMING, val,
    card->ext_csd.generic_cmd6_time,
    @@ -1160,8 +1159,7 @@ int mmc_hs400_to_hs200(struct mmc_card *
    mmc_set_clock(host, max_dtr);

    /* Switch HS400 to HS DDR */
    - val = EXT_CSD_TIMING_HS |
    - card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
    + val = EXT_CSD_TIMING_HS;
    err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
    val, card->ext_csd.generic_cmd6_time,
    true, send_status, true);
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