PCI/ASPM: Fix L1SS issues

[PATCH 0/3] PCI/ASPM: Fix L1SS issues

Posted by Bjorn Helgaas 3 years, 6 months ago

From: Bjorn Helgaas <bhelgaas@google.com>

This is really late, but I think we have two significant issues with L1SS:

  1) pcie_aspm_cap_init() reads from the L1SS capability even when it
  doesn't exist, so it reads PCI_COMMAND and PCI_STATUS instead and treats
  those as an L1SS Capability value.

  2) encode_l12_threshold() encodes LTR_L1.2_THRESHOLD as smaller than
  requested, so ports may enter L1.2 when they should not.

These patches are intended to fix both issues.

Bjorn Helgaas (3):
  PCI/ASPM: Factor out L1 PM Substates configuration
  PCI/ASPM: Ignore L1 PM Substates if device lacks capability
  PCI/ASPM: Correct LTR_L1.2_THRESHOLD computation

 drivers/pci/pcie/aspm.c | 155 +++++++++++++++++++++++-----------------
 1 file changed, 90 insertions(+), 65 deletions(-)

-- 
2.25.1

Re: [PATCH 0/3] PCI/ASPM: Fix L1SS issues

Posted by Sathyanarayanan Kuppuswamy 3 years, 6 months ago


On 10/4/22 7:58 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> This is really late, but I think we have two significant issues with L1SS:
> 
>   1) pcie_aspm_cap_init() reads from the L1SS capability even when it
>   doesn't exist, so it reads PCI_COMMAND and PCI_STATUS instead and treats
>   those as an L1SS Capability value.
> 
>   2) encode_l12_threshold() encodes LTR_L1.2_THRESHOLD as smaller than
>   requested, so ports may enter L1.2 when they should not.
> 
> These patches are intended to fix both issues.

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

> 
> Bjorn Helgaas (3):
>   PCI/ASPM: Factor out L1 PM Substates configuration
>   PCI/ASPM: Ignore L1 PM Substates if device lacks capability
>   PCI/ASPM: Correct LTR_L1.2_THRESHOLD computation
> 
>  drivers/pci/pcie/aspm.c | 155 +++++++++++++++++++++++-----------------
>  1 file changed, 90 insertions(+), 65 deletions(-)
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

Re: [PATCH 0/3] PCI/ASPM: Fix L1SS issues

Posted by Bjorn Helgaas 3 years, 6 months ago

On Tue, Oct 04, 2022 at 08:28:07PM -0700, Sathyanarayanan Kuppuswamy wrote:
> On 10/4/22 7:58 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> > 
> > This is really late, but I think we have two significant issues with L1SS:
> > 
> >   1) pcie_aspm_cap_init() reads from the L1SS capability even when it
> >   doesn't exist, so it reads PCI_COMMAND and PCI_STATUS instead and treats
> >   those as an L1SS Capability value.
> > 
> >   2) encode_l12_threshold() encodes LTR_L1.2_THRESHOLD as smaller than
> >   requested, so ports may enter L1.2 when they should not.
> > 
> > These patches are intended to fix both issues.
> 
> Looks good to me.
> 
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Thanks a lot for taking a look at these!  I put them on pci/aspm for
v6.1.

> > Bjorn Helgaas (3):
> >   PCI/ASPM: Factor out L1 PM Substates configuration
> >   PCI/ASPM: Ignore L1 PM Substates if device lacks capability
> >   PCI/ASPM: Correct LTR_L1.2_THRESHOLD computation
> > 
> >  drivers/pci/pcie/aspm.c | 155 +++++++++++++++++++++++-----------------
> >  1 file changed, 90 insertions(+), 65 deletions(-)
> > 
> 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer