Re: [PATCH v3 1/2] clk: qcom: dispcc-sc7180: Only park display clks at init

[Johan Hovold <johan@kernel.org>]

On Wed, Aug 28, 2024 at 10:17:07AM -0700, Stephen Boyd wrote:
> Amit Pundir reports that audio and USB-C host mode stops working on
> sm8550 after commit 01a0a6cc8cfd ("clk: qcom: Park shared RCGs upon
> registration"). That's because the gcc_usb30_prim_master_clk_src clk is
> registered and clk_rcg2_shared_init() parks it on XO. Running USB at a
> slower speed than the link supports is effectively under-clocking the
> USB link and probably confusing the downstream USB devices.
> 
> We didn't need to change all the shared RCGs to park on XO at
> registration time in commit commit 01a0a6cc8cfd ("clk: qcom: Park shared
> RCGs upon registration"). Instead, we only needed to park the few
> display related clks on sc7180 to fix the issue.
> 
> Fix sm8550 (and likely other qcom SoCs) by skipping the parking part of
> clk_rcg2_shared_init(). Make that the default init clk_op for shared
> RCGs, but keep the part where we cache the config register as that's
> still necessary to figure out the true parent of the clk is. Introduce
> another set of clk_ops 'clk_rcg2_shared_init_park' that does what
> clk_rcg2_shared_init() was doing and use that for the display clks on
> sc7180. This fixes the sm8550 problem and limits the "park upon
> registration" logic to the display clks that need it.
> 
> Fixes: 01a0a6cc8cfd ("clk: qcom: Park shared RCGs upon registration")
> Cc: Konrad Dybcio <konradybcio@kernel.org>
> Cc: Bjorn Andersson <andersson@kernel.org>
> Cc: Taniya Das <quic_tdas@quicinc.com>
> Cc: Neil Armstrong <neil.armstrong@linaro.org>
> Reported-by: Amit Pundir <amit.pundir@linaro.org>
> Closes: https://lore.kernel.org/CAMi1Hd1KQBE4kKUdAn8E5FV+BiKzuv+8FoyWQrrTHPDoYTuhgA@mail.gmail.com
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

I can confirm that this fixes the earlycon issue on x1e80100 that Bryan
reported here:

	https://lore.kernel.org/lkml/20240823-x1e80100-clk-fix-v1-1-0b1b4f5a96e8@linaro.org/

Perhaps you can drop the "dispcc-sc7180:" prefix from Subject when
applying (or resending) since this fixes a regression on multiple
Qualcomm SoCs. For example, use something like:

	clk: qcom: Only park sc7180 display clks at init

Tested-by: Johan Hovold <johan+linaro@kernel.org>

Johan