Re: [PATCH v3 2/2] mfd: intel-lpss: use devm_ioremap_uc for MMIO
From: Luis Chamberlain
Date: Thu Oct 10 2019 - 08:08:27 EST
On Wed, Oct 09, 2019 at 09:03:35PM -0600, Tuowen Zhao wrote:
> 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
> Tested-by: AceLan Kao <acelan.kao@xxxxxxxxxxxxx>
> Signed-off-by: Tuowen Zhao <ztuowen@xxxxxxxxx>
> Acked-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
I think you'll want to Cc stable for this, as well as the last patch.
LTS kernels with the ioremap_uc will be able to leverage the fix.