• Russell King's avatar
    mmc: sdhci-of-esdhc: set DMA snooping based on DMA coherence · 121bd08b
    Russell King authored
    We must not unconditionally set the DMA snoop bit; if the DMA API is
    assuming that the device is not DMA coherent, and the device snoops the
    CPU caches, the device can see stale cache lines brought in by
    speculative prefetch.
    This leads to the device seeing stale data, potentially resulting in
    corrupted data transfers.  Commonly, this results in a descriptor fetch
    error such as:
    mmc0: ADMA error
    mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
    mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00002202
    mmc0: sdhci: Blk size:  0x00000008 | Blk cnt:  0x00000001
    mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
    mmc0: sdhci: Present:   0x01f50008 | Host ctl: 0x00000038
    mmc0: sdhci: Power:     0x00000003 | Blk gap:  0x00000000
    mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x000040d8
    mmc0: sdhci: Timeout:   0x00000003 | Int stat: 0x00000001
    mmc0: sdhci: Int enab:  0x037f108f | Sig enab: 0x037f108b
    mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00002202
    mmc0: sdhci: Caps:      0x35fa0000 | Caps_1:   0x0000af00
    mmc0: sdhci: Cmd:       0x0000333a | Max curr: 0x00000000
    mmc0: sdhci: Resp[0]:   0x00000920 | Resp[1]:  0x001d8a33
    mmc0: sdhci: Resp[2]:   0x325b5900 | Resp[3]:  0x3f400e00
    mmc0: sdhci: Host ctl2: 0x00000000
    mmc0: sdhci: ADMA Err:  0x00000009 | ADMA Ptr: 0x000000236d43820c
    mmc0: sdhci: ============================================
    mmc0: error -5 whilst initialising SD card
    but can lead to other errors, and potentially direct the SDHCI
    controller to read/write data to other memory locations (e.g. if a valid
    descriptor is visible to the device in a stale cache line.)
    Fix this by ensuring that the DMA snoop bit corresponds with the
    behaviour of the DMA API.  Since the driver currently only supports DT,
    use of_dma_is_coherent().  Note that device_get_dma_attr() can not be
    used as that risks re-introducing this bug if/when the driver is
    converted to ACPI.
    Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
    Acked-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>