[Intel-gfx] [PATCH] drm/i915/display: mode clock check related to max dotclk frequency

[Navare, Manasi]

On Wed, Nov 09, 2022 at 12:36:44PM +0200, Jani Nikula wrote:
> On Wed, 09 Nov 2022, Nischal Varide <nischal.varide at intel.com> wrote:
> > A check on mode->clock to see if is greater than i915->max_dotclk_freq
> > or greater than 2 * (i915_max_dotclk_freq) in case of big-joiner and
> > return an -EINVAL in both the cases
> 
> The commit message should explain *why* the change is being done.
> 
> >
> > Signed-off-by: Nischal Varide <nischal.varide at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 7400d6b4c587..813f4c369dda 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -995,6 +995,10 @@ intel_dp_mode_valid(struct drm_connector *_connector,
> >  		bigjoiner = true;
> >  		max_dotclk *= 2;
> >  	}
> > +
> > +	if (mode->clock > max_dotclk)
> > +		return -EINVAL;
> > +
> 
> The return type of this function is enum drm_mode_status, which
> indicates the reason for rejecting the mode. It's not a negative error
> code.
> 
> Near the top of the function we have "target_clock = mode->clock;"
> making the above identical to the check we already have below. Apart
> from the incorrect return code.
> 
> What are you trying to do?
> 
> BR,
> Jani.

Yes I agree with Jani here that since target_clock is mode->clock we
already have that check in place and infact returing MODE_CLOCK_HIGH
makes more sense than returning just a -EINVAL

What is the purpose of this change?

Manasi

> 
> 
> >  	if (target_clock > max_dotclk)
> >  		return MODE_CLOCK_HIGH;
> 
> 
> 
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center