Re: [PATCH 8/8] i2c: nomadik: reduce FIFO flush timeout to avoid long interrupt handling

[Linus Walleij <linusw@kernel.org>]

On Tue, Nov 3, 2026 at 9:30 AM Dmitry Guzman <Dmitry.Guzman@mobileye.com> wrote:

> In flush_i2c_fifo(), the driver sets FTX and FRX flags and waits until
> they are reset (these bits are self-clearing). If after the first read
> one or both of these bits is set, it waits until both are reset. The
> timeout is 10 * I2C transfer timeout. I2C transfer timeout is by default
> 200 milliseconds. 2 seconds are much more than needed: as stated in the
> comment above, the flushing operation takes just several cycles before
> completed.
>
> flush_i2c_fifo() is called from init_hw() that may be called from
> interrupt handler. So, if the I2C controller is stuck and the FIFO does
> not get flushed, the CPU may spend up to 2 seconds in the interrupt
> handler and cause watchdog timeout or other unwanted consequences.
> Moreover, if the interrupt is handled by the same CPU core that updates
> jiffies, the loop may not finish at all.
>
> To avoid too long waiting, reduce the timeout to 100 microseconds and
> use read_poll_timeout_atomic() instead of relying on jiffies.
>
> Fixes: 3f9900f17cdb ("i2c: Add support for Ux500/Nomadik I2C controller")

Is it really "fixing" that? I don't know if I agree that this is an error
in the initial submission in 2010...

>
> Signed-off-by: Dmitry Guzman <Dmitry.Guzman@mobileye.com>

Surplus newline above? Maintainer can remove it when applying.
Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij