Re: [PATCH v2 3/9] PCI/ASPM: Use RMW accessors for changing LNKCTL

[Ilpo Järvinen]

On Mon, 19 Jun 2023, Bjorn Helgaas wrote:

> On Mon, Jun 19, 2023 at 05:45:06PM +0300, Ilpo Järvinen wrote:
> > On Fri, 16 Jun 2023, Lukas Wunner wrote:
> > > On Wed, May 17, 2023 at 01:52:29PM +0300, Ilpo Järvinen wrote:
> > > > Don't assume that the device is fully under the control of ASPM and use
> > > > RMW capability accessors which do proper locking to avoid losing
> > > > concurrent updates to the register values.
> > > > 
> > > > If configuration fails in pcie_aspm_configure_common_clock(), the
> > > > function attempts to restore the old PCI_EXP_LNKCTL_CCC settings. Store
> > > > only the old PCI_EXP_LNKCTL_CCC bit for the relevant devices rather
> > > > than the content of the whole LNKCTL registers. It aligns better with
> > > > how pcie_lnkctl_clear_and_set() expects its parameter and makes the
> > > > code more obvious to understand.
> > > [...]
> > > > @@ -224,17 +223,14 @@ static bool pcie_retrain_link(struct pcie_link_state *link)
> > > >  	if (!pcie_wait_for_retrain(parent))
> > > >  		return false;
> > > >  
> > > > -	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
> > > > -	reg16 |= PCI_EXP_LNKCTL_RL;
> > > > -	pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
> > > > +	pcie_capability_set_word(parent, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_RL);
> > > >  	if (parent->clear_retrain_link) {
> > > 
> > > This and several other RMW operations in drivers/pci/pcie/aspm.c
> > > are touched by commit b1689799772a ("PCI/ASPM: Use distinct local
> > > vars in pcie_retrain_link()") which got applied to pci/enumeration
> > > this week:
> > > 
> > > https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=enumeration&id=b1689799772a6f4180f918b0ff66e264a3db9796
> > > 
> > > As a result the $SUBJECT_PATCH no longer applies cleanly and needs
> > > to be respun.
> > 
> > Okay but I'm a bit lost which commit/head in pci repo I should now base 
> > this series because there's a conflict between pci/aspm and 
> > pci/enumeration which is not resolved in the repo because pci/enumeration 
> > hasn't advanced into pci/next yet. Any suggestion?
> 
> Generally speaking I prefer patches based on the PCI "main" branch
> (usually -rc1) because I base topic branches on that.  If there are
> conflicts with other pending material, it's great if you can mention
> them, but I can resolve them when applying, so no need to repost just
> for that.

Just to confirm I'm understanding this correctly... Am I supposed to send
a patch whose changelog description and diff do not agree?? (The diff 
will still modify pcie/aspm.c if it's main-based and the description 
refers to something more generic as per Lukas' request since the code got 
moved into pci.c in the enumeration branch).


-- 
 i.