Re: [PATCH v3 09/17] drm/imagination: Implement power management

[Maxime Ripard <mripard@redhat.com>]

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On Tue, Jun 13, 2023 at 03:47:52PM +0100, Sarah Walker wrote:
> @@ -503,21 +506,31 @@ pvr_device_init(struct pvr_device *pvr_dev)
>       if (err)
>               goto err_device_clk_fini;
>
> +     /* Explicitly power the GPU so we can access control registers before the FW is booted. */
> +     err = pm_runtime_resume_and_get(dev);
> +     if (err)
> +             goto err_device_clk_fini;
> +
>       /* Map the control registers into memory. */
>       err = pvr_device_reg_init(pvr_dev);
>       if (err)
> -             goto err_device_clk_fini;
> +             goto err_pm_runtime_put;
>
>       /* Perform GPU-specific initialization steps. */
>       err = pvr_device_gpu_init(pvr_dev);
>       if (err)
>               goto err_device_reg_fini;
>
> +     pm_runtime_put_autosuspend(dev);
> +

You probably can use pm_runtime_put here

> @@ -532,12 +545,17 @@ pvr_device_init(struct pvr_device *pvr_dev)
>  void
>  pvr_device_fini(struct pvr_device *pvr_dev)
>  {
> +     struct drm_device *drm_dev = from_pvr_device(pvr_dev);
> +     struct device *dev = drm_dev->dev;
> +
>       /*
>        * Deinitialization stages are performed in reverse order compared to
>        * the initialization stages in pvr_device_init().
>        */
> +     pm_runtime_get_sync(dev);
>       pvr_device_gpu_fini(pvr_dev);
>       pvr_device_reg_fini(pvr_dev);

AFAIK gpu_fini releases the firmware and reg_fini drops the register
mapping address, I don't think you need the device powered up for that.

> @@ -130,6 +133,20 @@ struct pvr_device {
>
>       /** @fw_dev: Firmware related data. */
>       struct pvr_fw_device fw_dev;
> +
> +     struct {
> +             /** @work: Work item for watchdog callback. */
> +             struct delayed_work work;
> +
> +             /** @old_kccb_cmds_executed: KCCB command execution count at last watchdog poll. */
> +             u32 old_kccb_cmds_executed;
> +
> +             /** @kccb_stall_count: Number of watchdog polls KCCB has been stalled for. */
> +             u32 kccb_stall_count;
> +     } watchdog;
> +
> +     /** @lost: %true if the device has been lost. */
> +     bool lost;

The device being "lost" isn't clear to me. Does it mean it's
unresponsive or stuck somehow?

> @@ -1285,9 +1303,15 @@ pvr_probe(struct platform_device *plat_dev)
>
>       platform_set_drvdata(plat_dev, drm_dev);
>
> +     devm_pm_runtime_enable(&plat_dev->dev);
> +
> +     pm_runtime_set_autosuspend_delay(&plat_dev->dev, 50);
> +     pm_runtime_use_autosuspend(&plat_dev->dev);
> +     pvr_power_init(pvr_dev);

The name threw me off a bit. It doesn't look like it's power related but
you init the watchdog timer?

I can't really tell from that patch, but if it's not done in a later
patch you'll probably need a call to sprinkle your driver with a few
_mark_last_busy calls (at least in the job submission path?)

Maxime

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