drm/msm/dsi: hs_zero timing

Werner Johansson werner.johansson at gmail.com
Wed Aug 26 11:22:00 PDT 2015

On Aug 26, 2015 10:46, "Rob Clark" <robdclark at gmail.com> wrote:
> btw, w/ some of these clk rounding issues, I suspect we need 'struct
> drm_display_mode' to be able to represent mode clock with greater
> accuracy than Khz..

Interesting point! However, in this case I had to adjust the clock hundreds
of kHz to make it tick over one step of hs_zero, so it might not be
absolutely necessary here. Do we need better than 10ppm accuracy for
display timing (assuming 100MHz pixel clock, 1kHz step size and that I did
the math correctly)? We don't even have kHz accuracy with the PLLs in the
QC platforms we currently use..

I think the rounding error happens with the smaller numbers / intermediate
results but maybe clock should be represented in Hz internally anyway? Not
sure if it's worth changing the external-facing representation though?

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