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    Subject[PATCH 4.14 014/100] mmc: sdhci-pci: Try "cd" for card-detect lookup before using NULL
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Rajat Jain <rajatja@google.com>

    commit cdcefe6bd9df754f528ffc339d3cc143cea4ddf6 upstream.

    Problem:

    The card detect IRQ does not work with modern BIOS (that want
    to use _DSD to provide the card detect GPIO to the driver).

    Details:

    The mmc core provides the mmc_gpiod_request_cd() API to let host drivers
    request the gpio descriptor for the "card detect" pin.
    This pin is specified in the ACPI for the SDHC device:

    * Either as a resource using _CRS. This is a method used by legacy BIOS.
    (The driver needs to tell which resource index).

    * Or as a named property ("cd-gpios"/"cd-gpio") in _DSD (which internally
    points to an entry in _CRS). This way, the driver can lookup using a
    string. This is what modern BIOS prefer to use.

    This API finally results in a call to the following code:

    struct gpio_desc *acpi_find_gpio(..., const char *con_id,...)
    {
    ...
    /* Lookup gpio (using "<con_id>-gpio") in the _DSD */
    ...
    if (!acpi_can_fallback_to_crs(adev, con_id))
    return ERR_PTR(-ENOENT);
    ...
    /* Falling back to _CRS is allowed, Lookup gpio in the _CRS */
    ...
    }

    Note that this means that if the ACPI has _DSD properties, the kernel
    will never use _CRS for the lookup (Because acpi_can_fallback_to_crs()
    will always be false for any device hat has _DSD entries).

    The SDHCI driver is thus currently broken on a modern BIOS, even if
    BIOS provides both _CRS (for index based lookup) and _DSD entries (for
    string based lookup). Ironically, none of these will be used for the
    lookup currently because:

    * Since the con_id is NULL, acpi_find_gpio() does not find a matching
    entry in DSDT. (The _DSDT entry has the property name = "cd-gpios")

    * Because ACPI contains DSDT entries, thus acpi_can_fallback_to_crs()
    returns false (because device properties have been populated from
    _DSD), thus the _CRS is never used for the lookup.

    Fix:

    Try "cd" for lookup in the _DSD before falling back to using NULL so
    as to try looking up in the _CRS.

    I've tested this patch successfully with both Legacy BIOS (that
    provide only _CRS method) as well as modern BIOS (that provide both
    _CRS and _DSD). Also the use of "cd" appears to be fairly consistent
    across other users of this API (other MMC host controller drivers).

    Link: https://lkml.org/lkml/2018/9/25/1113
    Signed-off-by: Rajat Jain <rajatja@google.com>
    Acked-by: Adrian Hunter <adrian.hunter@intel.com>
    Fixes: f10e4bf6632b ("gpio: acpi: Even more tighten up ACPI GPIO lookups")
    Cc: stable@vger.kernel.org
    Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/mmc/host/sdhci-pci-core.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/drivers/mmc/host/sdhci-pci-core.c
    +++ b/drivers/mmc/host/sdhci-pci-core.c
    @@ -1607,8 +1607,13 @@ static struct sdhci_pci_slot *sdhci_pci_
    host->mmc->caps2 |= MMC_CAP2_NO_PRESCAN_POWERUP;

    if (slot->cd_idx >= 0) {
    - ret = mmc_gpiod_request_cd(host->mmc, NULL, slot->cd_idx,
    + ret = mmc_gpiod_request_cd(host->mmc, "cd", slot->cd_idx,
    slot->cd_override_level, 0, NULL);
    + if (ret && ret != -EPROBE_DEFER)
    + ret = mmc_gpiod_request_cd(host->mmc, NULL,
    + slot->cd_idx,
    + slot->cd_override_level,
    + 0, NULL);
    if (ret == -EPROBE_DEFER)
    goto remove;


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