Re: [PATCH v2 2/6] drm/tilcdc: Write to LCDC_END_OF_INT_IND_REG at the end of IRQ function

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 15/06/16 11:39, Jyri Sarha wrote:
> Reorder the IRQ function so that the write to LCDC_END_OF_INT_IND_REG
> is done last. The write to LCDC_END_OF_INT_IND_REG indicates to LCDC
> that the interrupt service routine has completed (see section
> 13.3.6.1.6 in AM335x TRM). This is needed if LCDC's ipgvmodirq module
> is configured for pulse interrupts.
> 
> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> ---
>  drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 4d8f9a5..1343717 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -725,14 +725,19 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)
>  			tilcdc_crtc->frame_intact = true;
>  	}
>  
> -	if (priv->rev == 2) {
> -		if (stat & LCDC_FRAME_DONE) {
> -			tilcdc_crtc->frame_done = true;
> -			wake_up(&tilcdc_crtc->frame_done_wq);
> -		}
> -		tilcdc_write(dev, LCDC_END_OF_INT_IND_REG, 0);
> +	if (priv->rev == 1)
> +		return IRQ_HANDLED;
> +	/* The rest is for revision 2 only */
> +
> +	if (stat & LCDC_FRAME_DONE) {
> +		tilcdc_crtc->frame_done = true;
> +		wake_up(&tilcdc_crtc->frame_done_wq);
>  	}
>  
> +	if (stat & LCDC_FIFO_UNDERFLOW)
> +		dev_err_ratelimited(dev->dev, "%s(0x%08x): FIFO underfow",
> +				    __func__, stat);

We do have underflow irq for rev1 too, don't we?

Why not just move the "if (priv->rev == 2) {" block to the end? Or maybe
extract the write to the LCDC_END_OF_INT_IND_REG from the current block,
and move only that to the end. Much less re-ordering needed for that.

 Tomi


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