linux-kernel - Re: [PATCH v2] clk: meson-gxbb: set fclk_div3 as CLK_IS

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Date:   Tue, 06 Nov 2018 19:49:21 +0100
From:   jbrunet@...libre.com
To:     Stephen Boyd <sboyd@...nel.org>, Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     Christian Hewitt <christianshewitt@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] clk: meson-gxbb: set fclk_div3 as CLK_IS_CRITICAL

On Tue, 2018-11-06 at 10:43 -0800, Stephen Boyd wrote:
> Quoting Jerome Brunet (2018-11-05 15:08:20)
> > From: Christian Hewitt <christianshewitt@...il.com>
> > 
> > On the Khadas VIM2 (GXM) and LePotato (GXL) board there are problems
> > with reboot; e.g. a ~60 second delay between issuing reboot and the
> > board power cycling (and in some OS configurations reboot will fail
> > and require manual power cycling).
> > 
> > Similar to 'commit c987ac6f1f088663b6dad39281071aeb31d450a8 ("clk:
> > meson-gxbb: set fclk_div2 as CLK_IS_CRITICAL")' the SCPI Cortex-M4
> > Co-Processor seems to depend on FCLK_DIV3 being operational.
> > 
> > Until commit 05f814402d6174369b3b29832cbb5eb5ed287059 ("clk:
> > meson: add fdiv clock gates"), this clock was modeled and left on by
> > the bootloader.
> > 
> > We don't have precise documentation about the SCPI Co-Processor and
> > its clock requirement so we are learning things the hard way.
> > 
> > Marking this clock as critical solves the problem but it should not
> > be viewed as final solution. Ideally, the SCPI driver should claim
> > these clocks. We also depends on some clock hand-off mechanism
> > making its way to CCF, to make sure the clock stays on between its
> > registration and the SCPI driver probe.
> > 
> > Fixes: 05f814402d61 ("clk: meson: add fdiv clock gates")
> > Signed-off-by: Christian Hewitt <christianshewitt@...il.com>
> > Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> > ---
> 
> I can toss this into clk-fixes?
> 

Sure, it would be great. Thx Stephen.