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    Subject[PATCH 5.4 35/50] mfd: intel-lpss: Use devm_ioremap_uc for MMIO
    Date
    From: Tuowen Zhao <ztuowen@gmail.com>

    commit a8ff78f7f773142eb8a8befe5a95dd6858ebd635 upstream.

    Some BIOS erroneously specifies write-combining BAR for intel-lpss-pci
    in MTRR. This will cause the system to hang during boot. If possible,
    this bug could be corrected with a firmware update.

    This patch use devm_ioremap_uc to overwrite/ignore the MTRR settings
    by forcing the use of strongly uncachable pages for intel-lpss.

    The BIOS bug is present on Dell XPS 13 7390 2-in-1:

    [ 0.001734] 5 base 4000000000 mask 6000000000 write-combining

    4000000000-7fffffffff : PCI Bus 0000:00
    4000000000-400fffffff : 0000:00:02.0 (i915)
    4010000000-4010000fff : 0000:00:15.0 (intel-lpss-pci)

    Link: https://bugzilla.kernel.org/show_bug.cgi?id=203485
    Cc: <stable@vger.kernel.org> # v4.19+
    Tested-by: AceLan Kao <acelan.kao@canonical.com>
    Signed-off-by: Tuowen Zhao <ztuowen@gmail.com>
    Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
    Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Tested-by: Roman Gilg <subdiff@gmail.com>
    Signed-off-by: Lee Jones <lee.jones@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/mfd/intel-lpss.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/mfd/intel-lpss.c
    +++ b/drivers/mfd/intel-lpss.c
    @@ -384,7 +384,7 @@ int intel_lpss_probe(struct device *dev,
    if (!lpss)
    return -ENOMEM;

    - lpss->priv = devm_ioremap(dev, info->mem->start + LPSS_PRIV_OFFSET,
    + lpss->priv = devm_ioremap_uc(dev, info->mem->start + LPSS_PRIV_OFFSET,
    LPSS_PRIV_SIZE);
    if (!lpss->priv)
    return -ENOMEM;

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