linux-kernel - Re: [PATCH 3/8] drm/ingenic: Use standard drm_atomic_helper_commit

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Date:   Tue, 10 Aug 2021 12:20:38 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        "H . Nikolaus Schaller" <hns@...delico.com>,
        Paul Boddie <paul@...die.org.uk>, list@...ndingux.net,
        Sam Ravnborg <sam@...nborg.org>, linux-mips@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] drm/ingenic: Use standard
 drm_atomic_helper_commit_tail

On Sun, Aug 08, 2021 at 03:45:21PM +0200, Paul Cercueil wrote:
> By making the CRTC's .vblank_enable() function return an error when it
> is known that the hardware won't deliver a VBLANK, we can drop the
> ingenic_drm_atomic_helper_commit_tail() function and use the standard
> drm_atomic_helper_commit_tail() function instead.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 28 ++++-------------------
>  1 file changed, 4 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index bc71ba44ccf4..3ed7c27a8dde 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -706,29 +706,6 @@ static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
>  	}
>  }
>  
> -static void ingenic_drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
> -{
> -	/*
> -	 * Just your regular drm_atomic_helper_commit_tail(), but only calls
> -	 * drm_atomic_helper_wait_for_vblanks() if priv->no_vblank.
> -	 */
> -	struct drm_device *dev = old_state->dev;
> -	struct ingenic_drm *priv = drm_device_get_priv(dev);
> -
> -	drm_atomic_helper_commit_modeset_disables(dev, old_state);
> -
> -	drm_atomic_helper_commit_planes(dev, old_state, 0);
> -
> -	drm_atomic_helper_commit_modeset_enables(dev, old_state);
> -
> -	drm_atomic_helper_commit_hw_done(old_state);
> -
> -	if (!priv->no_vblank)
> -		drm_atomic_helper_wait_for_vblanks(dev, old_state);
> -
> -	drm_atomic_helper_cleanup_planes(dev, old_state);
> -}
> -
>  static irqreturn_t ingenic_drm_irq_handler(int irq, void *arg)
>  {
>  	struct ingenic_drm *priv = drm_device_get_priv(arg);
> @@ -749,6 +726,9 @@ static int ingenic_drm_enable_vblank(struct drm_crtc *crtc)
>  {
>  	struct ingenic_drm *priv = drm_crtc_get_priv(crtc);
>  
> +	if (priv->no_vblank)
> +		return -EWOULDBLOCK;

I think other drivers return EINVAL here. I'm not sure exactly this is
specified, but the errno here is visible to userspace.

Maybe would be good to update the kerneldoc for this hook?

Anyway this is great, with the errno fixed:

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

> +
>  	regmap_update_bits(priv->map, JZ_REG_LCD_CTRL,
>  			   JZ_LCD_CTRL_EOF_IRQ, JZ_LCD_CTRL_EOF_IRQ);
>  
> @@ -856,7 +836,7 @@ static const struct drm_mode_config_funcs ingenic_drm_mode_config_funcs = {
>  };
>  
>  static struct drm_mode_config_helper_funcs ingenic_drm_mode_config_helpers = {
> -	.atomic_commit_tail = ingenic_drm_atomic_helper_commit_tail,
> +	.atomic_commit_tail = drm_atomic_helper_commit_tail,
>  };
>  
>  static void ingenic_drm_unbind_all(void *d)
> -- 
> 2.30.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch