On Sun, May 25, 2025 at 12:23:03AM +0530, Manivannan Sadhasivam wrote:
> host_bridge::reset_slot() is supposed to reset the PCI root port/slot. Once
> that happens, the config space content would be lost. This was reported by
> Niklas on the dw-rockchip based platform where the MPS setting of the root
> port was lost after the host_bridge::reset_slot() callback. Hence, save the
> config space before calling the host_bridge::reset_slot() callback and
> restore it afterwards.
>
> While at it, make sure that the callback is only called for root ports by
> checking if the bridge is behind the root bus.
>
> Fixes: d5c1e1c25b37 ("PCI/ERR: Add support for resetting the slots in a platform specific way")
> Reported-by: Niklas Cassel <cassel@xxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-pci/aC9OrPAfpzB_A4K2@ryzen
> Suggested-by: Lukas Wunner <lukas@xxxxxxxxx>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> ---
> drivers/pci/pci.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 4d396bbab4a8..6d6e9ce2bbcc 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4985,10 +4985,19 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
> struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> int ret;
>
> - if (host->reset_slot) {
> + if (pci_is_root_bus(dev->bus) && host->reset_slot) {
> + /*
> + * Save the config space of the root port before doing the
> + * reset, since the state could be lost. The device state
> + * should've been saved by the caller.
> + */
> + pci_save_state(dev);
> ret = host->reset_slot(host, dev);
> if (ret)
> pci_err(dev, "failed to reset slot: %d\n", ret);
> + else
> + /* Now restore it on success */
> + pci_restore_state(dev);
>
> return;
> }
> --
> 2.43.0
>
Looks good to me:
Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>
