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

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Date:   Tue, 10 Aug 2021 12:46:05 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     David Airlie <airlied@...ux.ie>,
        "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

Hi Daniel,

Le mar., août 10 2021 at 12:20:38 +0200, Daniel Vetter 
<daniel@...ll.ch> a écrit :
> 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>

I thought about it afterwards, that my error code wasn't great. In my 
mind it was "the driver will hang while waiting for vblank" hence 
-EWOULDBLOCK ;)

I'll need to v2 anyway so I'll change it to -EINVAL then.

Cheers,
-Paul

> 
>>  +
>>   	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