Re: [PATCH v3] PCI/ASPM: Disable L1 before disabling L1ss

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jun 05, 2025 at 11:23:02AM +0000, Macpaul Lin (林智斌) wrote:
> On Tue, 2024-10-22 at 17:30 -0500, Bjorn Helgaas wrote:
> > On Mon, Oct 07, 2024 at 08:59:17AM +0530, Ajay Agarwal wrote:
> > > The current sequence in the driver for L1ss update is as follows.
> > > 
> > > Disable L1ss
> > > Disable L1
> > > Enable L1ss as required
> > > Enable L1 if required
> > > 
> > > With this sequence, a bus hang is observed during the L1ss
> > > disable sequence when the RC CPU attempts to clear the RC L1ss
> > > register after clearing the EP L1ss register. It looks like the
> > > RC attempts to enter L1ss again and at the same time, access to
> > > RC L1ss register fails because aux clk is still not active.
> > > 
> > > PCIe spec r6.2, section 5.5.4, recommends that setting either
> > > or both of the enable bits for ASPM L1 PM Substates must be done
> > > while ASPM L1 is disabled. My interpretation here is that
> > > clearing L1ss should also be done when L1 is disabled. Thereby,
> > > change the sequence as follows.
> > > 
> > > Disable L1
> > > Disable L1ss
> > > Enable L1ss as required
> > > Enable L1 if required
> > > 
> > > Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
> > 
> > Applied to pci/aspm for v6.13, thank you, Ajay!
> 
> Thanks! MediaTek also found this issue will happen on some old kernel,
> for example 6.11 or 6.12. would you please pick this patch also to some
> stable tree?
> 
> LINK:https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/pci/pcie/aspm.c?id=7447990137bf06b2aeecad9c6081e01a9f47f2aa

Please submit it properly, with your signed-off-by and we will be glad
to consider it.

thanks,

greg k-h