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From:   Tuowen Zhao <ztuowen@gmail.com>
To:     lee.jones@linaro.org, linux-kernel@vger.kernel.org
Cc:     andriy.shevchenko@linux.intel.com, mika.westerberg@linux.intel.com,
        acelan.kao@canonical.com, bhelgaas@google.com,
        kai.heng.feng@canonical.com, mcgrof@kernel.org,
        Tuowen Zhao <ztuowen@gmail.com>
Subject: [PATCH v3 2/2] mfd: intel-lpss: use devm_ioremap_uc for MMIO
Date:   Wed,  9 Oct 2019 21:03:35 -0600
Message-Id: <20191010030335.204974-2-ztuowen@gmail.com>
In-Reply-To: <20191010030335.204974-1-ztuowen@gmail.com>
References: <20191010030335.204974-1-ztuowen@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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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@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>
---
 drivers/mfd/intel-lpss.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
index bfe4ff337581..b0f0781a6b9c 100644
--- 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;
-- 
2.23.0