Re: [PATCH v2 04/22] drm: Don't test for IRQ support in VBLANK ioctls

From: Liviu Dudau <liviu.dudau@arm.com>
To: Thomas Zimmermann <tzimmermann@suse.de>
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Subject: Re: [PATCH v2 04/22] drm: Don't test for IRQ support in VBLANK ioctls
Date: Tue, 22 Jun 2021 16:25:04 +0100	[thread overview]
Message-ID: <20210622152504.2sw6khajwydsoaqa@e110455-lin.cambridge.arm.com> (raw)
In-Reply-To: <20210622141002.11590-5-tzimmermann@suse.de>

Hello,

On Tue, Jun 22, 2021 at 04:09:44PM +0200, Thomas Zimmermann wrote:
> For KMS drivers, replace the IRQ check in VBLANK ioctls with a check for
> vblank support. IRQs might be enabled wthout vblanking being supported.
> 
> This change also removes the DRM framework's only dependency on IRQ state
> for non-legacy drivers. For legacy drivers with userspace modesetting,
> the original test remains in drm_wait_vblank_ioctl().
> 
> v2:
> 	* keep the old test for legacy drivers in
> 	  drm_wait_vblank_ioctl() (Daniel)
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_irq.c    | 10 +++-------
>  drivers/gpu/drm/drm_vblank.c | 13 +++++++++----
>  2 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index c3bd664ea733..1d7785721323 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -74,10 +74,8 @@
>   * only supports devices with a single interrupt on the main device stored in
>   * &drm_device.dev and set as the device paramter in drm_dev_alloc().
>   *
> - * These IRQ helpers are strictly optional. Drivers which roll their own only
> - * need to set &drm_device.irq_enabled to signal the DRM core that vblank
> - * interrupts are working. Since these helpers don't automatically clean up the
> - * requested interrupt like e.g. devm_request_irq() they're not really
> + * These IRQ helpers are strictly optional. Since these helpers don't automatically
> + * clean up the requested interrupt like e.g. devm_request_irq() they're not really
>   * recommended.
>   */
>  
> @@ -91,9 +89,7 @@
>   * and after the installation.
>   *
>   * This is the simplified helper interface provided for drivers with no special
> - * needs. Drivers which need to install interrupt handlers for multiple
> - * interrupts must instead set &drm_device.irq_enabled to signal the DRM core
> - * that vblank interrupts are available.
> + * needs.
>   *
>   * @irq must match the interrupt number that would be passed to request_irq(),
>   * if called directly instead of using this helper function.
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 3417e1ac7918..a98a4aad5037 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -1748,8 +1748,13 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
>  	unsigned int pipe_index;
>  	unsigned int flags, pipe, high_pipe;
>  
> -	if (!dev->irq_enabled)
> -		return -EOPNOTSUPP;
> +	if  (drm_core_check_feature(dev, DRIVER_MODESET)) {
> +		if (!drm_dev_has_vblank(dev))
> +			return -EOPNOTSUPP;
> +	} else {
> +		if (!dev->irq_enabled)
> +			return -EOPNOTSUPP;
> +	}

For a system call that is used quite a lot by userspace we have increased the code size
in a noticeable way. Can we not cache it privately?

Best regards,
Liviu

>  
>  	if (vblwait->request.type & _DRM_VBLANK_SIGNAL)
>  		return -EINVAL;
> @@ -2023,7 +2028,7 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
>  	if (!drm_core_check_feature(dev, DRIVER_MODESET))
>  		return -EOPNOTSUPP;
>  
> -	if (!dev->irq_enabled)
> +	if (!drm_dev_has_vblank(dev))
>  		return -EOPNOTSUPP;
>  
>  	crtc = drm_crtc_find(dev, file_priv, get_seq->crtc_id);
> @@ -2082,7 +2087,7 @@ int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data,
>  	if (!drm_core_check_feature(dev, DRIVER_MODESET))
>  		return -EOPNOTSUPP;
>  
> -	if (!dev->irq_enabled)
> +	if (!drm_dev_has_vblank(dev))
>  		return -EOPNOTSUPP;
>  
>  	crtc = drm_crtc_find(dev, file_priv, queue_seq->crtc_id);
> -- 
> 2.32.0
> 

-- 
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