On Fri, Aug 2, 2024 at 7:12 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> On Fri, Jul 26, 2024 at 05:28:29PM +0800, Huacai Chen wrote:
> > This is similar to commit 62b6dee1b44aa23b39355 ("PCI/portdrv: Prevent
> > LS7A Bus Master clearing on shutdown"), which prevents LS7A Bus Master
> > clearing on kexec.
> >
> > Only skip Bus Master clearing on bridges because endpoint devices still
> > need it.
>
> I think we need some explanation here and a hint in the comment below
> about why this is needed.
>
> I guess the point is to work around the LS7A defect that clearing
> PCI_COMMAND_MASTER prevents MMIO requests from going downstream, and
> we may need to do that even after .shutdown(), e.g., to print console
> messages?
>
> And in this case we rely on .shutdown() for the downstream devices to
> disable interrupts and DMA?
Yes, this is the key point, I will add the above information to the
commit message.
>
> s/62b6dee1b44aa23b39355/62b6dee1b44a/
OK, thanks.
Huacai
>
> > Signed-off-by: Ming Wang <wangming01@xxxxxxxxxxx>
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > ---
> > drivers/pci/pci-driver.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index f412ef73a6e4..b7d3a4d8532f 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -517,7 +517,7 @@ static void pci_device_shutdown(struct device *dev)
> > * If it is not a kexec reboot, firmware will hit the PCI
> > * devices with big hammer and stop their DMA any way.
> > */
> > - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
> > + if (kexec_in_progress && !pci_is_bridge(pci_dev) && (pci_dev->current_state <= PCI_D3hot))
> > pci_clear_master(pci_dev);
> > }
> >
> > --
> > 2.43.5
> >
