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

[Jani Nikula]

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.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center