• Brian Norris's avatar
    mmc: core: Set HS clock speed before sending HS CMD13 · 4bc31ede
    Brian Norris authored
    Way back in commit 4f25580f ("mmc: core: changes frequency to
    hs_max_dtr when selecting hs400es"), Rockchip engineers noticed that
    some eMMC don't respond to SEND_STATUS commands very reliably if they're
    still running at a low initial frequency. As mentioned in that commit,
    JESD84-B51 P49 suggests a sequence in which the host:
    1. sets HS_TIMING
    2. bumps the clock ("<= 52 MHz")
    3. sends further commands
    
    It doesn't exactly require that we don't use a lower-than-52MHz
    frequency, but in practice, these eMMC don't like it.
    
    The aforementioned commit tried to get that right for HS400ES, although
    it's unclear whether this ever truly worked as committed into mainline,
    as other changes/refactoring adjusted the sequence in conflicting ways:
    
    08573eaf ("mmc: mmc: do not use CMD13 to get status after speed mode
    switch")
    
    53e60650 ("mmc: core: Allow CMD13 polling when switching to HS mode
    for mmc")
    
    In any case, today we do step 3 before step 2. Let's fix that, and also
    apply the same logic to HS200/400, where this eMMC has problems too.
    
    Resolves errors like this seen when booting some RK3399 Gru/Scarlet
    systems:
    
    [    2.058881] mmc1: CQHCI version 5.10
    [    2.097545] mmc1: SDHCI controller on fe330000.mmc [fe330000.mmc] using ADMA
    [    2.209804] mmc1: mmc_select_hs400es failed, error -84
    [    2.215597] mmc1: error -84 whilst initialising MMC card
    [    2.417514] mmc1: mmc_select_hs400es failed, error -110
    [    2.423373] mmc1: error -110 whilst initialising MMC card
    [    2.605052] mmc1: mmc_select_hs400es failed, error -110
    [    2.617944] mmc1: error -110 whilst initialising MMC card
    [    2.835884] mmc1: mmc_select_hs400es failed, error -110
    [    2.841751] mmc1: error -110 whilst initialising MMC card
    
    Ealier versions of this patch bumped to 200MHz/HS200 speeds too early,
    which caused issues on, e.g., qcom-msm8974-fairphone-fp2. (Thanks for
    the report Luca!) After a second look, it appears that aligns with
    JESD84 / page 45 / table 28, so we need to keep to lower (HS / 52 MHz)
    rates first.
    
    Fixes: 08573eaf ("mmc: mmc: do not use CMD13 to get status after speed mode switch")
    Fixes: 53e60650 ("mmc: core: Allow CMD13 polling when switching to HS mode for mmc")
    Fixes: 4f25580f ("mmc: core: changes frequency to hs_max_dtr when selecting hs400es")
    Cc: Shawn Lin <shawn.lin@rock-chips.com>
    Link: https://lore.kernel.org/linux-mmc/11962455.O9o76ZdvQC@g550jk/Reported-by: default avatarLuca Weiss <luca@z3ntu.xyz>
    Signed-off-by: default avatarBrian Norris <briannorris@chromium.org>
    Tested-by: default avatarLuca Weiss <luca@z3ntu.xyz>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/r/20220422100824.v4.1.I484f4ee35609f78b932bd50feed639c29e64997e@changeidSigned-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
    4bc31ede
mmc.c 61.2 KB