On Sun, May 11, 2025 at 04:34:13PM +0800, Huacai Chen wrote:
> This is similar to commit 62b6dee1b44a ("PCI/portdrv: Prevent LS7A Bus
> Master clearing on shutdown"), which prevents LS7A Bus Master clearing
> on kexec.
>
So 62b6dee1b44a never worked as intented because the PCI core still cleared bus
master bit?
> The key point of this 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.
>
> Only skip Bus Master clearing on bridges because endpoint devices still
> need it.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> 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 602838416e6a..8a1e32367a06 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))
I'm not a Kexec expert, but wouldn't not clearing the bus mastering for all PCI
bridges safe? You are making a generic change for a defect in your hardware, so
it might not apply to all other hardwares.
- Mani
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