linux-kernel - Re: [PATCH v1] PCI / PM: Really allow runtime PM without callback functions

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Message-ID: <CAJZ5v0huF=T_QH_Vzfmq07x2L_BPdCCdZSKzKOMYY19s37kjOw@mail.gmail.com>
Date: Tue, 13 Feb 2024 15:02:11 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Raag Jadav <raag.jadav@...el.com>
Cc: bhelgaas@...gle.com, jarkko.nikula@...ux.intel.com, 
	mika.westerberg@...ux.intel.com, andriy.shevchenko@...ux.intel.com, 
	stanislaw.gruszka@...ux.intel.com, lukas@...ner.de, rafael@...nel.org, 
	ilpo.jarvinen@...ux.intel.com, linux-pci@...r.kernel.org, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	gregkh@...uxfoundation.org, sashal@...nel.org
Subject: Re: [PATCH v1] PCI / PM: Really allow runtime PM without callback functions

On Mon, Feb 12, 2024 at 7:32 AM Raag Jadav <raag.jadav@...el.com> wrote:
>
> Commit c5eb1190074c ("PCI / PM: Allow runtime PM without callback
> functions") tried to eliminate the need for runtime PM callbacks
> by modifying pci_pm_runtime_suspend() and pci_pm_runtime_resume(),
> but didn't modify pci_pm_runtime_idle() with relevant changes, which
> still returns -ENOSYS if the driver supplies no runtime PM callbacks.
>
> Fix this by modifying pci_pm_runtime_idle() such that it allows PCI
> device power state transitions without runtime PM callbacks.
>
>  0)               |  pm_runtime_work() {
>  0)               |    rpm_idle() {
>  0)               |      rpm_check_suspend_allowed() {
>  0)   1.500 us    |        __dev_pm_qos_resume_latency(); /* = 0x7fffffff */
>  0)   4.840 us    |      } /* rpm_check_suspend_allowed = 0x0 */
>  0)   1.550 us    |      __rpm_get_callback(); /* = 0xffffffffb4bc84f0 */
>  0)   1.800 us    |      pci_pm_runtime_idle(); /* = -38 */
>  0) + 17.070 us   |    } /* rpm_idle = -38 */
>  0) + 22.450 us   |  } /* pm_runtime_work = -38 */
>
> Debugged-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Raag Jadav <raag.jadav@...el.com>
> Tested-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>

Acked-by: Rafael J. Wysocki <rafael@...nel.org>

> ---
>
> This is not marked for linux-stable for the need of extensive testing
> and can be backported after a few releases if no issues are reported.
>
>  drivers/pci/pci-driver.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 51ec9e7e784f..bb7f6775b350 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1382,10 +1382,7 @@ static int pci_pm_runtime_idle(struct device *dev)
>         if (!pci_dev->driver)
>                 return 0;
>
> -       if (!pm)
> -               return -ENOSYS;
> -
> -       if (pm->runtime_idle)
> +       if (pm && pm->runtime_idle)
>                 return pm->runtime_idle(dev);
>
>         return 0;
> --
> 2.35.3
>
>