Re: [PATCH 2/4] PCI/PTM: Enable PTM when restoring state

Sathyanarayanan Kuppuswamy
2022-09-02T17:25:59Z

On 9/2/22 7:58 AM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> The suspend path may disable PTM before saving config state, which means
> the PCI_PTM_CTRL_ENABLE bit in the saved state may be cleared even though
> we want PTM to be enabled when resuming.

If suspend is disabling PTM separately, why not enable it during the resume
operation? Why club it with PTM state restoration?

>
> If "dev->ptm_enabled" is set, it means PTM should be enabled, so make sure
> PCI_PTM_CTRL_ENABLE is set when restoring the PTM state.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
> drivers/pci/pcie/ptm.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index b6a417247ce3..3115601a85ef 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -82,6 +82,14 @@ void pci_restore_ptm_state(struct pci_dev *dev)
> return;
>
> cap = (u16 *)&save_state->cap.data[0];
> +
> + /*
> + * The suspend path may disable PTM before saving config state.
> + * Make sure PCI_PTM_CTRL_ENABLE is set if PTM should be enabled.
> + */
> + if (dev->ptm_enabled)
> + *cap |= PCI_PTM_CTRL_ENABLE;
> +
> pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap);
> }
>

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer