Re: [PATCH i-g-t] tests/kms_invalid_mode: Allow clock-too-high test on non-Intel platforms

["Jason-JH Lin (林睿祥)" <Jason-JH.Lin@mediatek.com>]

Hi Jani,

Thanks for the suggestion!
  
On Tue, 2026-04-14 at 13:44 +0300, Jani Nikula wrote:
> On Tue, 14 Apr 2026, Jason-JH Lin <jason-jh.lin@mediatek.com> wrote:
> > The clock-too-high subtest was being skipped on non-Intel platforms
> > because igt_get_max_dotclock() returns 0 when reading from
> > Intel-specific debugfs fails.
> > 
> > This change allows the test to run on all platforms by:
> > - Using a clearly invalid clock value (10 GHz) when max_dotclock is
> >   unavailable, which any reasonable driver should reject
> > - Restricting bigjoiner/ultrajoiner logic to Intel devices only
> > 
> > This prevents the test from being marked as IGNORED/SKIP on non-
> > Intel
> > platforms while maintaining the original test intent of verifying
> > that
> > drivers properly reject modes with excessively high clock rates.
> > 
> > Tested on MTK platforms where the test now properly executes and
> > verifies invalid clock validation.
> 
> I think overall we'll need a framework to ask platform/device
> specific
> things instead of portraying the services as generic, like
> igt_get_max_dotclock().
> 

As for a more general platform/device-specific query framework,
I agree that would be beneficial for broader igt development,
and could be implemented in the future.

> > 
> > Signed-off-by: Jason-JH Lin <jason-jh.lin@mediatek.com>
> > ---
> >  tests/kms_invalid_mode.c | 38 +++++++++++++++++++++++-------------
> > --
> >  1 file changed, 23 insertions(+), 15 deletions(-)
> > 
> > diff --git a/tests/kms_invalid_mode.c b/tests/kms_invalid_mode.c
> > index 5edffb649ef4..18d79e59c736 100644
> > --- a/tests/kms_invalid_mode.c
> > +++ b/tests/kms_invalid_mode.c
> > @@ -126,7 +126,13 @@ adjust_mode_clock_too_high(data_t *data,
> > drmModeModeInfoPtr mode)
> >  {
> >  	int max_dotclock = data->max_dotclock;
> >  
> > -	igt_require(max_dotclock != 0);
> > +	/*
> > +	 * If max_dotclock is unavailable (e.g., non-Intel
> > platforms),
> > +	 * use an obviously invalid value that any driver should
> > reject.
> > +	 * 10 GHz is well beyond any reasonable hardware
> > capability.
> > +	 */
> > +	if (max_dotclock == 0)
> > +		max_dotclock = 10000000;  /* 10 GHz in kHz */
> 
> Not a fan of using magic numbers like this.
> 
> Perhaps
> 
> 	if (!max_dotclock) {
> 		mode->clock = -1;
> 		return;
> 	}
> 
> would be less magic?
> 

For this particular test, since the intention is to always supply an
obviously invalid clock value to ensure proper driver validation,
I will set mode->clock = -1 in case max_dotclock is unavailable,
as you proposed.

This avoids magic numbers and keeps the original logic for Intel
platforms, so there should be no regression on previously tested
systems.

I'll send a new revision with the change.

Regards,
Jason-JH Lin