[PATCH v3 3/3] gpu: ipu-v3: pre: don't use fixed timeout when waiting for safe window

[Philipp Zabel]

On Fr, 2024-05-17 at 12:45 +0200, Lucas Stach wrote:
> The timeout when waiting for the PRE safe window is rather short, as
> normally we would only need to wait a few dozen usecs for the problematic
> scanline region to pass and we don't want to spin too long in case
> something goes wrong. This however mixes badly with preemption, as we
> can easily get scheduled away from the CPU for a longer time than our
> timeout, in which case we would hit a spurious timeout and wrongly skip
> the PRE update.
> 
> Instead of disabling preemption across the wait loop, potentially
> impacting the overall system latency, use a wait loop with a fixed
> max number of iterations, so time spent away from the CPU is not
> accounted against the timeout budget.
> 
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>

Reviewed-by: Philipp Zabel <p.zabel at pengutronix.de>

regards
Philipp