[PATCH v4 2/2] mfd: intel-lpss: use devm_ioremap_uc for MMIO

From: Tuowen Zhao
Date: Mon Oct 14 2019 - 11:36:28 EST


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@xxxxxxxxxxxxxxx>
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>
Acked-for-MFD-by: Lee Jones <lee.jones@xxxxxxxxxx>
---
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