On 22-10-27, Marek Vasut wrote:
> On 10/27/22 10:13, Marco Felsch wrote:
>
> Hi,
>
> [...]
>
> > > diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > > b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > > index a5302006c02cd..aee7babb5fa5c 100644
> > > --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > > +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > > @@ -341,6 +341,18 @@ static void lcdif_enable_controller(struct
> > > lcdif_drm_private *lcdif)
> > > reg = readl(lcdif->base + LCDC_V8_CTRLDESCL0_5);
> > > reg |= CTRLDESCL0_5_EN;
> > > writel(reg, lcdif->base + LCDC_V8_CTRLDESCL0_5);
> > > +
> > > + /* Set FIFO Panic watermarks, low 1/3, high 2/3 . */
> > > + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_RANGE / 3) |
> > > + FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_RANGE / 3),
> > > + lcdif->base + LCDC_V8_PANIC0_THRES);
> > > +
> > > + /*
> > > + * Enable FIFO Panic, this does not generate interrupt, but
> > > + * boosts NoC priority based on FIFO Panic watermarks.
> > > + */
> > > + writel(INT_ENABLE_D1_PLANE_PANIC_EN,
> > > + lcdif->base + LCDC_V8_INT_ENABLE_D1);
> >
> > Out of curiosity since we have a patch doing the exact same thing but
> > didn't saw any improvements. Is there a reason why you enabled it here?
>
> It seems like the right thing to do here, when enabling the controller.
>
> > We did this during lcdif_rpm_resume(). But as I said with a 1080P
> > display we still saw the flickering, it disappeared first after rising
> > the burst-size.
>
> That's what the NXP downstream driver does too, isn't it ? That seems like
> the wrong place to me.
Yes, I think so. It's not about the place (if it wrong/correct) it is
more about the PANIC mode itself. I'm curios about:
1) Do you still see the flickering with this patch and without the
"burst-size increase" patch?
2) Do you still saw flickering after the "burst-size increase" patch
applied and without this patch?
I had no 4K display therefore I'm asking, but with 1080P we didn't saw
any improvements without increasing the burst-size. My assumption was:
if the panic mode does work, than I don't have to increase the
burst-size.
Regards,
Marco
