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SubjectRe: [PATCH] drm/bridge/synopsys: dsi: use adjusted_mode in mode_set
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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@st.com> 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@st.com>
>>> ---
>>> 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@chromium.org>
>>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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

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