Re: [PATCH] clk: qcom: gcc-sc8280xp: don't use parking clk_ops for QUPs

Stephen Boyd
2024-09-03T20:02:25Z

Quoting Johan Hovold (2024-09-02 00:08:30)
> A recent change started parking the RCG at an always on parent during
> registration, something which specifically breaks handover from an early
> serial console.
>
> Quoting Stephen Boyd who fixed this issue for SM8550 [1]:
>
> The QUPs aren't shared in a way that requires parking the RCG at
> an always on parent in case some other entity turns on the clk.
> The hardware is capable of setting a new frequency itself with
> the DFS mode, so parking is unnecessary. Furthermore, there
> aren't any GDSCs for these devices, so there isn't a possibility
> of the GDSC turning on the clks for housekeeping purposes.
>
> This wasn't a problem to mark these clks shared until we started
> parking shared RCGs at clk registration time in commit
> 01a0a6cc8cfd ("clk: qcom: Park shared RCGs upon registration").
> Parking at init is actually harmful to the UART when earlycon is
> used. If the device is pumping out data while the frequency
> changes you'll see garbage on the serial console until the
> driver can probe and actually set a proper frequency.
>
> Fixes: 01a0a6cc8cfd ("clk: qcom: Park shared RCGs upon registration")
> Fixes: d65d005f9a6c ("clk: qcom: add sc8280xp GCC driver")
> Link: https://lore.kernel.org/all/20240819233628.2074654-2-swboyd@chromium.org/ [1]
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---

Applied to clk-fixes