[PATCH v2 4/5] drm: hdlcd: Don't touch vsync interrupts during vblank enable/disable.

[Daniel Vetter]

On Wed, Jun 01, 2016 at 03:48:38PM +0100, Liviu Dudau wrote:
> Because the HDLCD lacks a hardware counter for vsync signal, the DRM
> framework expects that the vsync interrupts are left running to feed
> the internal software counter. Currently the HDLCD is masking/unmasking
> the vsync interrupt on vblank enable/disable calls, which break that
> expectation. Fix that.
> 
> Signed-off-by: Liviu Dudau <Liviu.Dudau at arm.com>

As discussed, this is actually not needed. The only thing you need to do
is set max_vblank_count = 0. If vblank enable/disable is causing problems,
then that would indicate an issue in the core drm_irq.c code, and should
be fixed there.

And if the docs are confusion, then please update those insted. This patch
here shouldn't be needed at all.
-Daniel

> ---
>  drivers/gpu/drm/arm/hdlcd_drv.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/hdlcd_drv.c b/drivers/gpu/drm/arm/hdlcd_drv.c
> index fb172d2..3f92dfa 100644
> --- a/drivers/gpu/drm/arm/hdlcd_drv.c
> +++ b/drivers/gpu/drm/arm/hdlcd_drv.c
> @@ -183,9 +183,13 @@ static int hdlcd_irq_postinstall(struct drm_device *drm)
>  
>  	/* enable debug interrupts */
>  	irq_mask |= HDLCD_DEBUG_INT_MASK;
> +#endif
> +
> +	/* enable vsync interrupts */
> +	irq_mask |= HDLCD_INTERRUPT_VSYNC;
>  
>  	hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, irq_mask);
> -#endif
> +
>  	return 0;
>  }
>  
> @@ -208,20 +212,11 @@ static void hdlcd_irq_uninstall(struct drm_device *drm)
>  
>  static int hdlcd_enable_vblank(struct drm_device *drm, unsigned int crtc)
>  {
> -	struct hdlcd_drm_private *hdlcd = drm->dev_private;
> -	unsigned int mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);
> -
> -	hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, mask | HDLCD_INTERRUPT_VSYNC);
> -
>  	return 0;
>  }
>  
>  static void hdlcd_disable_vblank(struct drm_device *drm, unsigned int crtc)
>  {
> -	struct hdlcd_drm_private *hdlcd = drm->dev_private;
> -	unsigned int mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);
> -
> -	hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, mask & ~HDLCD_INTERRUPT_VSYNC);
>  }
>  
>  #ifdef CONFIG_DEBUG_FS
> -- 
> 2.8.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch