> Save the ACS Control register in pci_save_state() and write it back > in pci_restore_state(), instead of recomputing the ACS controls from > scratch with pci_enable_acs(). > > This makes ACS symmetric with the rest of a device's saved state. Today > pci_save_state() ignores ACS entirely and pci_restore_state() re-enables > the ACS controls from the kernel's current ACS policy. As a result, a > device can come out of a reset with different ACS controls than it went > in with, e.g. any controls programmed outside of pci_enable_acs() are > silently dropped. > > pci_enable_acs() runs when a driver binds to a device > (pci_dma_configure()), i.e. after pci_bus_add_device() has already saved > the device's state. Refresh the saved ACS Control register there as > well, otherwise a subsequent reset would revert ACS back to the > configuration left behind by firmware. > > Devices that rely on device-specific quirks to enable an ACS equivalent > keep that configuration outside of the ACS Control register, so keep > configuring ACS from scratch for them. Do the same for devices that have > no saved ACS state at all. > > Reviewed-by: Bjorn Helgaas <[email protected]> > Assisted-by: Claude:claude-opus-5 > Signed-off-by: David Matlack <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=8
