Re: [PATCH v13 09/35] gpu: host1x: Add runtime PM and OPP support

[Ulf Hansson]

On Mon, 27 Sept 2021 at 00:42, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> Add runtime PM and OPP support to the Host1x driver. 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 are missing the
> RPM handling and we're going to remove some of these paths in the future.
>
> 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>
> ---

[...]

> --- a/drivers/gpu/host1x/dev.c
> +++ b/drivers/gpu/host1x/dev.c
> @@ -6,14 +6,18 @@
>   */
>
>  #include <linux/clk.h>
> +#include <linux/delay.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/io.h>
>  #include <linux/list.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
>  #include <linux/of.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>
> +#include <soc/tegra/common.h>
> +
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/host1x.h>
>  #undef CREATE_TRACE_POINTS
> @@ -190,6 +194,9 @@ static void host1x_setup_sid_table(struct host1x *host)
>         const struct host1x_info *info = host->info;
>         unsigned int i;
>
> +       if (!info->has_hypervisor)
> +               return;
> +
>         for (i = 0; i < info->num_sid_entries; i++) {
>                 const struct host1x_sid_entry *entry = &info->sid_table[i];
>
> @@ -347,6 +354,27 @@ static void host1x_iommu_exit(struct host1x *host)
>         }
>  }
>
> +static int host1x_get_resets(struct host1x *host)
> +{
> +       int err;
> +
> +       host->resets[0].id = "mc";
> +       host->resets[1].id = "host1x";
> +       host->nresets = ARRAY_SIZE(host->resets);
> +
> +       err = devm_reset_control_bulk_get_optional_exclusive_released(
> +                               host->dev, host->nresets, host->resets);
> +       if (err) {
> +               dev_err(host->dev, "failed to get reset: %d\n", err);
> +               return err;
> +       }
> +
> +       if (WARN_ON(!host->resets[1].rstc))
> +               return -ENOENT;
> +
> +       return 0;
> +}
> +
>  static int host1x_probe(struct platform_device *pdev)
>  {
>         struct host1x *host;
> @@ -423,12 +451,9 @@ 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 +468,10 @@ 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;
> -       }
> -
>         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 +480,18 @@ static int host1x_probe(struct platform_device *pdev)
>                 goto deinit_syncpt;
>         }
>
> -       host1x_debug_init(host);
> +       pm_runtime_enable(&pdev->dev);
> +
> +       err = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
> +       if (err)
> +               goto pm_disable;
>
> -       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 (err)
> +               goto pm_disable;
> +
> +       host1x_debug_init(host);
>
>         err = host1x_register(host);
>         if (err < 0)
> @@ -486,13 +507,14 @@ static int host1x_probe(struct platform_device *pdev)
>         host1x_unregister(host);
>  deinit_debugfs:
>         host1x_debug_deinit(host);
> +
> +       pm_runtime_put(&pdev->dev);

pm_runtime_put() is asynchronous, so it may not actually succeed to
trigger the ->runtime_suspend() callback to be invoked. Thus, this
could end up that we leave clocks prepared/enabled when ->probe()
fails, for example.

I guess pm_runtime_put_sync_suspend() is slightly better.

Another option is to call pm_runtime_force_suspend(), but then you
must skip the call pm_runtime_disable() afterwards, as that has
already been done inside that function.

> +pm_disable:
> +       pm_runtime_disable(&pdev->dev);
> +
>         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:
> @@ -507,19 +529,94 @@ static int host1x_remove(struct platform_device *pdev)
>
>         host1x_unregister(host);
>         host1x_debug_deinit(host);
> +
> +       pm_runtime_put(&pdev->dev);

Similar comment as in ->probe().

> +       pm_runtime_disable(&pdev->dev);
> +
>         host1x_intr_deinit(host);
>         host1x_syncpt_deinit(host);
> -       reset_control_assert(host->rst);
> -       clk_disable_unprepare(host->clk);
>         host1x_iommu_exit(host);
>
>         return 0;
>  }
>
> +
> +       host1x_setup_sid_table(host);
> +       host1x_syncpt_restore(host);
> +       host1x_intr_start(host);
> +
> +       return 0;
> +
> +disable_clk:
> +       clk_disable_unprepare(host->clk);
> +release_reset:
> +       reset_control_bulk_release(host->nresets, host->resets);
> +
> +       return err;
> +}
> +
> +static const struct dev_pm_ops host1x_pm = {
> +       SET_RUNTIME_PM_OPS(host1x_runtime_suspend, host1x_runtime_resume,
> +                          NULL)
> +       /* TODO: add system suspend-resume once driver will be ready for that */
> +};

[...]

Kind regards
Uffe