Handling DP compliance short pulse for DP MST

Handling DP compliance short pulse for DP MST

[Manasi Navare]

Hi,

I have been working on adding DP compliance test request support in
i915 driver. Unigraf DPR-120 is used as a DP Compliance reference 
sink device that generates a short pulse for the compliance test requests.
In case of DP SST, these short pulses get handled in the i915 driver's
short pulse handler (intel_dp_short_pulse). This has been successfully working
to run the DP compliance tests for DP SST. The next step is to handle the DP
compliance short pulses for DP MST. However in case of MST, it also recieves 
short pulses for the sideband traffic from the branch device. This gets handled
in the DRM layer. Since the short pulses for MST get handled in drm layer, should
the compliance short pulses for MST also be handled in DRM layer? In this case,
DRM will read process the short pulse in DRM and call the Compliance test handler
in i915 driver through a function pointer. 

Any thoughts on this implementation of DP compliance support for MST?

Regards
Manasi
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Re: Handling DP compliance short pulse for DP MST

[Dave Airlie]

On 9 September 2016 at 11:28, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Hi,
>
> I have been working on adding DP compliance test request support in
> i915 driver. Unigraf DPR-120 is used as a DP Compliance reference
> sink device that generates a short pulse for the compliance test requests.
> In case of DP SST, these short pulses get handled in the i915 driver's
> short pulse handler (intel_dp_short_pulse). This has been successfully working
> to run the DP compliance tests for DP SST. The next step is to handle the DP
> compliance short pulses for DP MST. However in case of MST, it also recieves
> short pulses for the sideband traffic from the branch device. This gets handled
> in the DRM layer. Since the short pulses for MST get handled in drm layer, should
> the compliance short pulses for MST also be handled in DRM layer? In this case,
> DRM will read process the short pulse in DRM and call the Compliance test handler
> in i915 driver through a function pointer.
>
> Any thoughts on this implementation of DP compliance support for MST?

How much of DP compliance is i915 specific, maybe it might make sense to move
some of the compliance handling up into the DRM helpers.

I don't think you need callbacks, you should get handled value back
from the core
MST handlers that say if they haven't handled the IRQ you also read
the ESI values in i915,
which should tell you if it's a test interrupt.

Dave.
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