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

[Lukas Wunner]

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.

Thanks,

Lukas