Re: [PATCH 07/13] i2c: nomadik: support short xfer timeouts using waitqueue & hrtimer

Linus Walleij
2024-02-19T14:20:04Z

On Thu, Feb 15, 2024 at 5:52 PM Théo Lebrun <theo.lebrun@bootlin.com> wrote:

> Replace the completion by a waitqueue for synchronization from IRQ
> handler to task. For short timeouts, use hrtimers, else use timers.
> Usecase: avoid blocking the I2C bus for too long when an issue occurs.
>
> The threshold picked is one jiffy: if timeout is below that, use
> hrtimers. This threshold is NOT configurable.
>
> Implement behavior but do NOT change fetching of timeout. This means the
> timeout is unchanged (200ms) and the hrtimer case will never trigger.
>
> A waitqueue is used because it supports both desired timeout approaches.
> See wait_event_timeout() and wait_event_hrtimeout(). An atomic boolean
> serves as synchronization condition.
>
> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>

Part of me want to go and fix completions to handle hrtimer timeouts
for submicrosecond timeouts, BUT I realized that this is a bit thick
request for a simple driver, so just a suggestion for something we could
do one day. This is fine with me.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij