[PATCH] drm/i915/gt: Ensure sleep calculations in wait_for_freq() do not use negative value of timeout_ms

[Krzysztof Karas]

> On Tue, 05 Aug 2025, Krzysztof Karas <krzysztof.karas at intel.com> wrote:
> > wait_for_freq() allows timeout_ms to be negative to pass it down
> > to msecs_to_jiffies(). If the argument to the latter function is
> > indeed negative, then MAX_JIFFY_OFFSET is returned from it.
> >
> > However, later in the wait_for_freq()'s "do while" loop,
> > "timeout_ms" is used to calculate a new value for "sleep", which
> > is a plain integer. While "sleep" being negative does not lead
> > to erroneous behavior, as the "sleep" is cast to unsigned type
> > in usleep_range(), it does not seem intentional.
> >
> > Change the type of "sleep" variable to unsigned and ensure it
> > does not use "timeout_ms", when it is a negative value in the
> > calculations.
> 
> That's an elaborate explanation for a case that never
> occurs. wait_for_freq() is used in three places with fixed timeout
> values.
Which means that whoever decides to pass a negative value here
in the future will be met with an unpleasant surprise when
looking at sleep values, because we never validate the input to
this function.
> 
> What's the real reason for the change?
Do you imply something was obscured?

This patch is supposed to try and fix mishandling of int type
variable, which represents time to sleep. Time should not be
represented by a negative value, unless we are going back in
time. Hence, the change to unsigned and additional check on
timeout_ms.

-- 
Best Regards,
Krzysztof