linux-kernel - Re: [PATCH V4] PCI/ASPM: Update saved buffers with latest ASPM

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Date: Thu, 22 Feb 2024 12:54:34 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: Vidya Sagar <vidyas@...dia.com>, bhelgaas@...gle.com, macro@...am.me.uk,
	ajayagarwal@...gle.com, ilpo.jarvinen@...ux.intel.com,
	david.e.box@...ux.intel.com, hkallweit1@...il.com,
	johan+linaro@...nel.org, xueshuai@...ux.alibaba.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	treding@...dia.com, jonathanh@...dia.com, kthota@...dia.com,
	mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V4] PCI/ASPM: Update saved buffers with latest ASPM

On Thu, Feb 22, 2024 at 10:20:06AM -0800, Kuppuswamy Sathyanarayanan wrote:
> On 2/22/24 9:44 AM, Vidya Sagar wrote:
> > Many PCIe device drivers save the configuration state of their respective
> > devices during probe and restore the same when their 'slot_reset' hook
> > is called through PCIe Error Recovery Handler.
> >
> > If the system has a change in ASPM policy after the driver's probe is
> > called and before error event occurred, 'slot_reset' hook restores the
> > PCIe configuration state to what it was at the time of probe but not to
> > what it was just before the occurrence of the error event.
> > This effectively leads to a mismatch in the ASPM configuration between
> > the device and its upstream parent device.
> >
> > Update the saved configuration state of the device with the latest info
> > whenever there is a change w.r.t ASPM policy.
> >
> > Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> > ---
> > V4:
> > * Rebased on top of pci/aspm branch
> >
> > V3:
> > * Addressed sathyanarayanan.kuppuswamy's review comments
> >
> > V2:
> > * Rebased on top of the tree code
> > * Addressed Bjorn's review comments
> >
> >  drivers/pci/pcie/aspm.c | 28 ++++++++++++++++++++++++++--
> >  3 files changed, 28 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index cfc5b84dc9c9..3db606ba9344 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1648,7 +1648,7 @@ static int pci_save_pcie_state(struct pci_dev *dev)
> >  	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &cap[i++]);
> >  	pcie_capability_read_word(dev, PCI_EXP_SLTCTL2, &cap[i++]);
> >  
> > -	pci_save_aspm_state(dev);
> > +	pci_save_aspm_l1ss_state(dev);
> >  	pci_save_ltr_state(dev);
> >  
> >  	return 0;
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index b217e74966eb..9fe78eb8b07d 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -95,7 +95,7 @@ void pci_msix_init(struct pci_dev *dev);
> >  bool pci_bridge_d3_possible(struct pci_dev *dev);
> >  void pci_bridge_d3_update(struct pci_dev *dev);
> >  void pci_aspm_get_l1ss(struct pci_dev *pdev);
> > -void pci_save_aspm_state(struct pci_dev *pdev);
> > +void pci_save_aspm_l1ss_state(struct pci_dev *pdev);
> 
> is this rename a review request? It is not clear from the commit log
> why you are doing it?

David's changes already on pci/aspm added pci_save_aspm_state(), but
it actually only saves L1SS data, and Vidya needs to save the non-L1SS
data also.

I think I'm going to rework David's changes a little bit so this is
named pci_save_aspm_l1ss_state() from the beginning so we won't need
the rename here.

Bjorn