[igt-dev] [RFC i-g-t] LPSP igt test on TGL

[Anshuman Gupta]

On 2020-02-27 at 14:44:18 +0200, Jani Nikula wrote:
> On Thu, 27 Feb 2020, Anshuman Gupta <anshuman.gupta at intel.com> wrote:
> > Above block diagram depicts lpsp on TGL, while earlier development of
> > lpsp igt test it has been assumed that every non-edp panel is not a
> > lpsp panel but it is not true on TGL, any HDMI/DP panel connected on
> > pipe A and connected to PORT_{A,B,C} is lpsp panel, and DSI panel is
> > also lpsp panel.
> >
> > Currently i915_pm_lpsp igt has been categorized in edp-native and non-edp subtest.
> > non-edp subtest require the fix to validate the lpsp panels.
> > My solution approach to check the port on which DP/HDMI connector is currently 
> > connected.
> > if (port <= PORT_C)
> >     lpsp_should_be_enabled.
> > else
> >     lpsp_should_be_disabled.
> >  
> > Currently there are two igt i915_pm_lpsp, i915_pm_rpm require to know
> > the port of DP/HDMI connector, so we need a igt library function for
> > that.
> >
> > I am looking to parse the i915_display_info to get the port
> > information, but at same time it seems a fragile solution to me as any
> > change in i915_display_info will break the test, but i don't have any
> > other idea to get the port information.
> >
> > Please provide your opinion and feedback for the above solution approach.
> 
> I'd add a connector specific debugfs file that tells you whether LPSS
> (Low Power Single Pipe, for those who want to know what the acronym
> means) is possible and whether it's enabled. Alternatively add the info
> about LPSS to i915_display_info. But AFAICT there's no need for
> userspace to know about the port. This also avoids reading the
> HSW_PWR_WELL_CTL2 register directly.
Thanks Jani and Ville for your feedback and suggestion, based upon your feedback
i have following solution approach.
Add a connector specific debugfs attributes i915_lpsp_cpable.
for ecah connector if it is lpsp capable, do modeset with pipe A crtc 
on that connector and validate if power wells above  pg2 are turned off
by using i915_power_domain_info. 

Thanks ,
Anshuman
> 
> BR,
> Jani.
> 
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center