Re: [PATCH v3 3/3] clk: qcom: Add display clock controller driver for SDM845

[Taniya Das]

On 7/9/2018 1:07 PM, Stephen Boyd wrote:
> Quoting Taniya Das (2018-07-09 00:07:21)
> > On 7/9/2018 11:46 AM, Stephen Boyd wrote:
> > > >    > Why is the nocache flag needed? Applies to all clks in this file.
> > > >    >
> > > >
> > > > This flag is required for all RCGs whose PLLs are controlled outside the
> > > > clock controller. The display code would require the recalculated rate
> > > > always.
> > >
> > > Right. Why is the PLL controlled outside of the clock controller? The
> > > rate should propagate upward to the PLL from here, so who's going
> > > outside of that?
> > The DSI0/1 PLL are not part of the display clock controller, but in the
> > display subsystem which are managed by the DRM drivers. When DRM drivers
> > query for the rate clock driver should always return the non cached rates.
>
> Why? Is the DSI PLL changing rate all the time, randomly, without going
> through the clk APIs to do so?

Hmm, I am afraid I do not have an answer for this, but this was the 
requirement to always return the non cached rates from the clock driver.

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