linux-kernel - Re: [PATCH] clk: qcom: gcc-x1e80100: Fix halt

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Date: Fri, 31 May 2024 13:55:49 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Abel Vesa <abel.vesa@...aro.org>, Bjorn Andersson <andersson@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Rajendra Nayak <quic_rjendra@...cinc.com>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc: Sibi Sankar <quic_sibis@...cinc.com>, linux-arm-msm@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: qcom: gcc-x1e80100: Fix halt_check for all 3 USB PHY
 pipe clocks

On 30.05.2024 6:48 PM, Abel Vesa wrote:
> Since the pipe clocks are fed by the QMP PHYs, they are not under the
> GCC control, therefore the halt bit might not get. This will lead to
> the clock driver reporting the clock as stuck, but that is inaccurate.
> So instead of waiting for the halt bit to get set, just use the
> HALT_DELAY flag.

I can see this being a good fix, however the commit message could use
some massaging.

The issue you're facing is that you can't toggle these branch clocks before
the QMPPHY has been fully initialized (as that initialization sequence
contains, among other things, setting up the internal PLL). We're doing the
HALT_SKIP thing to hack away the complexity of coming back to this. In a
perfect world, we'd "defer" the toggle requests and all code that makes
these, but it sounds overly complex for what it is. So in essence, the
clock could really be stuck.

And FWIW, you missed gcc_usb3_mp_phy_pipe_[01]_clk, and these are orphans
which could use some fixing up as well.

Konrad