Quoting Sankeerth Billakanti (2022-05-05 11:02:36)
Quoting Douglas Anderson (2022-04-25 14:06:42)
Having 'a' in 'vdda' typically means 'analog' for 'analog' circuits, so I'd expect this to only matter for the phy that contains the analog circuitry. It would be great to remove the regulator code from drivers/gpu/drm/msm/dp/dp_power.c and move
the
regulator_set_load() call to the phy driver if possible. Hopefully qcom folks can help clarify here.
Interesting. Oddly enough, the sc7280 datasheet doesn't list the "_A". It calls these "VDD_VREF_0P9" and "VDD_VREF_1P2". However, on the schematic in front of me someone labeled these pins on the sc7280 with the "A". ...and the driver looks for a supply with the "a". :-/
It would be good to get clarification from someone with better
information.
-Doug
Our internal power grid documents list the regulators as VDD_A_*_1P2 and VDD_A_*_0P9 for all the platforms.
Do your internal power grid documents indicate what these supplies are powering? The question is if these supplies power any of the logic inside the eDP controller or if they only supply power to the analog circuits in the eDP phy. If it's the eDP phy only then the regulator usage in the eDP driver should be removed. I would suspect this is the case because the controller is probably all digital logic and runs at the typical 1.8V that the rest of the SoC uses. Similarly, these are voltage references which sound like a PLL reference voltage.
Please clarify this further.
For the DP driver using the usb-dp combo phy, there were cases where the usb driver was turning off the phy and pll regulators whenever usb-dp concurrent mode need not be supported. This caused phy and pll to be powered down causing aux transaction failures and display blankouts. From then on, it became a practice for the controller driver to vote for the phy and pll regulators also.
So, as a practice, we put the same name in the DT files. Hence,
Reviewed-by: Sankeerth Billakanti quic_sbillaka@quicinc.com