linux-kernel - Re: [PATCH v2 2/2] PCI/PTM: fix to maintain pci_dev->ptm

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Date:   Fri, 15 Jul 2022 13:46:43 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Rajvi Jingar <rajvi.jingar@...ux.intel.com>
Cc:     Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        David Box <david.e.box@...ux.intel.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] PCI/PTM: fix to maintain pci_dev->ptm_enabled

On Fri, Jul 15, 2022 at 1:16 AM Rajvi Jingar
<rajvi.jingar@...ux.intel.com> wrote:
>
> pci_dev->ptm_enabled needs to be maintained to reflect the current PTM
> state of the device. In pci_ptm_disable(), clear ptm_enabled from
> 'struct pci_dev' on disabling PTM state for the device.
> In pci_restore_ptm_state(), set dev->ptm_enabled based on the restored
> PTM state of the device.
>
> Also, perform ptm_enabled check in pci_ptm_disable() to avoid config
> space access in case if PTM is already disabled for the device.
>
> Signed-off-by: Rajvi Jingar <rajvi.jingar@...ux.intel.com>
> ---
>  v1->v2:
>    - add ptm_enabled check in pci_ptm_disable().
>    - set the dev->ptm_enabled value in pci_restore_ptm_state().
> ---
>  drivers/pci/pcie/ptm.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index 368a254e3124..8dc7d2285a0d 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -34,6 +34,9 @@ void pci_disable_ptm(struct pci_dev *dev)
>         int ptm;
>         u16 ctrl;
>
> +       if (!dev->ptm_enabled)
> +               return;
> +
>         if (!pci_is_pcie(dev))
>                 return;

After the check you've added this doesn't need to be checked any more,
because ptm_enabled will not be set if pci_is_pcie(dev) is not true
AFAICS.

Otherwise the patch looks good to me, so with the above addressed,
please feel free to add

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

to it.

Thanks!

>
> @@ -44,6 +47,7 @@ void pci_disable_ptm(struct pci_dev *dev)
>         pci_read_config_word(dev, ptm + PCI_PTM_CTRL, &ctrl);
>         ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT);
>         pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl);
> +       dev->ptm_enabled = 0;
>  }
>
>  void pci_save_ptm_state(struct pci_dev *dev)
> @@ -83,6 +87,7 @@ void pci_restore_ptm_state(struct pci_dev *dev)
>
>         cap = (u16 *)&save_state->cap.data[0];
>         pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap);
> +       dev->ptm_enabled = !!(*cap & PCI_PTM_CTRL_ENABLE);
>  }
>
>  void pci_ptm_init(struct pci_dev *dev)
> --
> 2.25.1
>