• Raul E Rangel's avatar
    mmc: core: Verify SD bus width · 48b759f4
    Raul E Rangel authored
    [ Upstream commit 9e4be8d0 ]
    
    The SD Physical Layer Spec says the following: Since the SD Memory Card
    shall support at least the two bus modes 1-bit or 4-bit width, then any SD
    Card shall set at least bits 0 and 2 (SD_BUS_WIDTH="0101").
    
    This change verifies the card has specified a bus width.
    
    AMD SDHC Device 7806 can get into a bad state after a card disconnect
    where anything transferred via the DATA lines will always result in a
    zero filled buffer. Currently the driver will continue without error if
    the HC is in this condition. A block device will be created, but reading
    from it will result in a zero buffer. This makes it seem like the SD
    device has been erased, when in actuality the data is never getting
    copied from the DATA lines to the data buffer.
    
    SCR is the first command in the SD initialization sequence that uses the
    DATA lines. By checking that the response was invalid, we can abort
    mounting the card.
    Reviewed-by: default avatarAvri Altman <avri.altman@wdc.com>
    Signed-off-by: default avatarRaul E Rangel <rrangel@chromium.org>
    Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    48b759f4
sd.c 29.5 KB