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Date:   Tue, 8 Oct 2019 12:18:04 +0300
From:   Mika Westerberg <mika.westerberg@linux.intel.com>
To:     Tuowen Zhao <ztuowen@gmail.com>
Cc:     lee.jones@linaro.org, linux-kernel@vger.kernel.org,
        andriy.shevchenko@linux.intel.com, acelan.kao@canonical.com,
        bhelgaas@google.com, kai.heng.feng@canonical.com, mcgrof@kernel.org
Subject: Re: [PATCH v2] mfd: intel-lpss: use devm_ioremap_uc for MMIO
Message-ID: <20191008091804.GB2819@lahna.fi.intel.com>
References: <20191007184231.13256-1-ztuowen@gmail.com>
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On Mon, Oct 07, 2019 at 12:42:31PM -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 adds devm_ioremap_uc as a new managed wrapper to ioremap_uc
> and with it overwrite the MTRR settings to force 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
> Signed-off-by: Tuowen Zhao <ztuowen@gmail.com>

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>