Re: [PATCH v8 11/34] gpu: host1x: Add runtime PM and OPP support

[Ulf Hansson]

On Tue, 17 Aug 2021 at 03:30, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> Add runtime PM and OPP support to the Host1x driver. It's required for
> enabling system-wide DVFS and supporting dynamic power management using
> a generic power domain. For the starter we will keep host1x always-on
> because dynamic power management require a major refactoring of the driver
> code since lot's of code paths will need the RPM handling and we're going
> to remove some of these paths in the future. Host1x doesn't consume much
> power so it is good enough, we at least need to resume Host1x in order
> to initialize the power state.
>
> Tested-by: Peter Geis <pgwipeout@xxxxxxxxx> # Ouya T30
> Tested-by: Paul Fertser <fercerpav@xxxxxxxxx> # PAZ00 T20
> Tested-by: Nicolas Chauvet <kwizart@xxxxxxxxx> # PAZ00 T20 and TK1 T124
> Tested-by: Matt Merhar <mattmerhar@xxxxxxxxxxxxxx> # Ouya T30
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> ---

[...]

> +
>  static int host1x_probe(struct platform_device *pdev)
>  {
>         struct host1x *host;
> @@ -394,6 +423,10 @@ static int host1x_probe(struct platform_device *pdev)
>         /* set common host1x device data */
>         platform_set_drvdata(pdev, host);
>
> +       err = devm_tegra_core_dev_init_opp_table_simple(&pdev->dev);
> +       if (err)
> +               return err;
> +
>         host->regs = devm_ioremap_resource(&pdev->dev, regs);
>         if (IS_ERR(host->regs))
>                 return PTR_ERR(host->regs);
> @@ -423,12 +456,9 @@ static int host1x_probe(struct platform_device *pdev)
>                 return err;
>         }
>
> -       host->rst = devm_reset_control_get(&pdev->dev, "host1x");
> -       if (IS_ERR(host->rst)) {
> -               err = PTR_ERR(host->rst);
> -               dev_err(&pdev->dev, "failed to get reset: %d\n", err);
> +       err = host1x_get_resets(host);
> +       if (err)
>                 return err;
> -       }
>
>         err = host1x_iommu_init(host);
>         if (err < 0) {
> @@ -443,22 +473,10 @@ static int host1x_probe(struct platform_device *pdev)
>                 goto iommu_exit;
>         }
>
> -       err = clk_prepare_enable(host->clk);
> -       if (err < 0) {
> -               dev_err(&pdev->dev, "failed to enable clock\n");
> -               goto free_channels;
> -       }
> -
> -       err = reset_control_deassert(host->rst);
> -       if (err < 0) {
> -               dev_err(&pdev->dev, "failed to deassert reset: %d\n", err);
> -               goto unprepare_disable;
> -       }
> -

Removing the clk_prepare_enable() and reset_control_deassert() from
host1x_probe(), might not be a good idea. See more about why, below.

>         err = host1x_syncpt_init(host);
>         if (err) {
>                 dev_err(&pdev->dev, "failed to initialize syncpts\n");
> -               goto reset_assert;
> +               goto free_channels;
>         }
>
>         err = host1x_intr_init(host, syncpt_irq);
> @@ -467,10 +485,14 @@ static int host1x_probe(struct platform_device *pdev)
>                 goto deinit_syncpt;
>         }
>
> -       host1x_debug_init(host);
> +       pm_runtime_enable(&pdev->dev);
>
> -       if (host->info->has_hypervisor)
> -               host1x_setup_sid_table(host);
> +       /* the driver's code isn't ready yet for the dynamic RPM */
> +       err = pm_runtime_resume_and_get(&pdev->dev);

If the driver is being built with the CONFIG_PM Kconfig option being
unset, pm_runtime_resume_and_get() will return 0 to indicate success -
and without calling the ->runtime_resume() callback.
In other words, the clock will remain gated and the reset will not be
deasserted, likely causing the driver to be malfunctioning.

If the driver isn't ever being built with CONFIG_PM unset, feel free
to ignore my above comments.

Otherwise, if it needs to work both with and without CONFIG_PM being
set, you may use the following pattern in host1x_probe() to deploy
runtime PM support:

"Enable the needed resources to probe the device"
pm_runtime_get_noresume()
pm_runtime_set_active()
pm_runtime_enable()

"Before successfully completing probe"
pm_runtime_put()

> +       if (err)
> +               goto deinit_intr;
> +
> +       host1x_debug_init(host);
>
>         err = host1x_register(host);
>         if (err < 0)
> @@ -486,13 +508,13 @@ static int host1x_probe(struct platform_device *pdev)
>         host1x_unregister(host);
>  deinit_debugfs:
>         host1x_debug_deinit(host);
> +
> +       pm_runtime_put(&pdev->dev);
> +       pm_runtime_disable(&pdev->dev);
> +deinit_intr:
>         host1x_intr_deinit(host);
>  deinit_syncpt:
>         host1x_syncpt_deinit(host);
> -reset_assert:
> -       reset_control_assert(host->rst);
> -unprepare_disable:
> -       clk_disable_unprepare(host->clk);
>  free_channels:
>         host1x_channel_list_free(&host->channel_list);
>  iommu_exit:

[...]

Kind regards
Uffe