Hi, In $subject, use MMIO instead of mmio.
On Fri, Sep 27, 2019 at 11:55:13AM -0600, Tuowen Zhao wrote: > Write-combining BAR for intel-lpss-pci in MTRR causes system hangs > during boot. > > This patch adds devm_ioremap_uc as a new managed wrapper to ioremap_uc > and with it forces the use of strongly uncachable mmio in intel-lpss. > > This bahavior is seen on Dell XPS 13 7390 2-in-1: > > [ 0.001734] 5 base 4000000000 mask 6000000000 write-combining I think it is worth mentioning that this is actually a BIOS bug and fixed by some vendors via BIOS upgrade. > 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 <[email protected]> > --- > drivers/mfd/intel-lpss.c | 2 +- > include/linux/io.h | 2 ++ > lib/devres.c | 19 +++++++++++++++++++ > 3 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c > index 277f48f1cc1c..06106c9320bb 100644 > --- a/drivers/mfd/intel-lpss.c > +++ b/drivers/mfd/intel-lpss.c > @@ -395,7 +395,7 @@ 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); Can you add a comment here explaining why this particular driver needs to use _uc version? Normally drivers call the plain devm_ioremap() and expect to get non-cached memory, however ioremap() (which resolves to ioremap_nocache()) does not touch x86 PAT configuration which is the reason we need to call _uc variant here. Otherwise looks good to me.
