Comment 0 for bug 1845584

AceLan Kao (acelankao) wrote :

[Impact]
The memory region intel-lpss-pci uses has been declared as
write-combining
[ 0.001728] 5 base 4000000000 mask 6000000000 write-combining
This leads to the system hangs up during booting up.

This is a BIOS issue, but there are some platforms on the market and users are struggling on booting up the machines. So, we may have to fix this in the kernel.

[Fix]
Tuowen Zhao(<email address hidden>)[1] provides a diff patch for intel-lpss
driver to claim to use un-catchable memory while calling
__devm_ioremap(), and it works well.

To avoid the potential impact on other machines, I add a quirk to list
the machines which has the write-combining area in MTRR which overlaps
with the address that intel-lpss uses, only the machines in the list
pass the DEVM_IOREMAP_UC to __devm_ioremap().

[Test]
Verified on Dell XPS 13 7390 2-in-1

[Regression Potential]
Low, without this patch, the machine even can't boot. And the quirk only for specific machines, so the modification won't affect other machines.

1. https://bugzilla.kernel.org/show_bug.cgi?id=203485#c23