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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, AceLan Kao <acelan.kao@canonical.com>,
        Tuowen Zhao <ztuowen@gmail.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Roman Gilg <subdiff@gmail.com>,
        Lee Jones <lee.jones@linaro.org>
Subject: [PATCH 5.4 35/50] mfd: intel-lpss: Use devm_ioremap_uc for MMIO
Date:   Fri,  8 May 2020 14:35:41 +0200
Message-Id: <20200508123048.223733664@linuxfoundation.org>
In-Reply-To: <20200508123043.085296641@linuxfoundation.org>
References: <20200508123043.085296641@linuxfoundation.org>
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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;