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

Ulf Hansson
2021-08-17T12:05:20Z

On Tue, 17 Aug 2021 at 03:30, Dmitry Osipenko <digetx@gmail.com> 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@gmail.com> # Ouya T30
> Tested-by: Paul Fertser <fercerpav@gmail.com> # PAZ00 T20
> Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20 and TK1 T124
> Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---

[...]

> +
> 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