Re: [PATCH] drm/bridge/synopsys: dsi: use adjusted_mode in mode_set

[Archit Taneja]

On 01/26/2018 03:24 PM, Philippe CORNU wrote:
> Hi Brian,
> And a big thanks for your Tested-by
>
> On 01/25/2018 11:47 PM, Brian Norris wrote:
> > On Thu, Jan 25, 2018 at 7:55 AM, Philippe Cornu <philippe.cornu@xxxxxx> wrote:
> > > The "adjusted_mode" clock value (ie the real pixel clock) is more
> > > accurate than "mode" clock value (ie the panel/bridge requested
> > > clock value). It offers a better preciseness for timing
> > > computations and allows to reduce the extra dsi bandwidth in
> > > burst mode (from ~20% to ~10-12%, hw platform dependant).
> > >
> > > Signed-off-by: Philippe Cornu <philippe.cornu@xxxxxx>
> > > ---
> > > Note: This patch replaces "drm/bridge/synopsys: dsi: add optional pixel clock"
> >
> > These two appear to be the same for my cases, but at least nothing breaks:
>
> In drivers/gpu/drm/rockchip/rockchip_drm_vop.c function
> vop_crtc_mode_fixup(), the adjusted_mode->clock (ie. vop px clk output =
> dw dsi px clk input) is updated according to rockchip hw pll/dividers...
>
> So you "may" have a different value in adjusted_mode->clock compare to
> mode->clock. Maybe there is no difference for the panel you are using
> because its px clock matches perfectly with rockchip hw pll/dividers...
> or has been set to match with ;-)
>
> I did a similar patch (see [1]) and it works "fine" on stm, the only
> difference with the rockchip vop is that clk_round_rate() returns odd
> values on stm so I used set/get_rate instead.
>
> So now, both rockchip & stm crtc have an "adjusted_mode->clock" so it
> makes sense to use it in dw dsi :)

Could you get the patch [1] queued on drm-misc-next? I can queue this patch
after it.

Thanks,
Archit

> Philippe :-)
>
> [1] https://patchwork.freedesktop.org/patch/200720/
> "[PATCH] drm/stm: ltdc: use crtc_mode_fixup to update adjusted_mode clock"
>
>
> > Tested-by: Brian Norris <briannorris@xxxxxxxxxxxx>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project