Re: [PATCH] drm/vc4: Remove broken attempt at GPU reset using genpd.

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Dec 21, 2015 at 06:08:44PM -0800, Eric Anholt wrote:
> I've tested and confirmed that it doesn't actually work.  We'll need
> to sort out how to do this properly later, but for now just remove it
> since it also caused build breakage due to using CONFIG_PM_SLEEP
> functions without our Kconfig depending on PM_SLEEP.
> 
> Signed-off-by: Eric Anholt <eric@anholt.net>

Still broken upstream.

FWIW:

Acked-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/gpu/drm/vc4/vc4_v3d.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_v3d.c b/drivers/gpu/drm/vc4/vc4_v3d.c
> index 424d515..314ff71 100644
> --- a/drivers/gpu/drm/vc4/vc4_v3d.c
> +++ b/drivers/gpu/drm/vc4/vc4_v3d.c
> @@ -144,19 +144,16 @@ int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused)
>  }
>  #endif /* CONFIG_DEBUG_FS */
>  
> -/*
> - * Asks the firmware to turn on power to the V3D engine.
> - *
> - * This may be doable with just the clocks interface, though this
> - * packet does some other register setup from the firmware, too.
> - */
>  int
>  vc4_v3d_set_power(struct vc4_dev *vc4, bool on)
>  {
> -	if (on)
> -		return pm_generic_poweroff(&vc4->v3d->pdev->dev);
> -	else
> -		return pm_generic_resume(&vc4->v3d->pdev->dev);
> +	/* XXX: This interface is needed for GPU reset, and the way to
> +	 * do it is to turn our power domain off and back on.  We
> +	 * can't just reset from within the driver, because the reset
> +	 * bits are in the power domain's register area, and get set
> +	 * during the poweron process.
> +	 */
> +	return 0;
>  }
>  
>  static void vc4_v3d_init_hw(struct drm_device *dev)
> -- 
> 2.6.2
> 
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