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

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Date:   Tue, 13 Nov 2018 17:38:29 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     stable@...r.kernel.org
CC:     Jerome Brunet <jbrunet@...libre.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        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

Hi Stable team,

Le 06/11/2018 00:08, Jerome Brunet a écrit :
> 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>


Could this patch go into the next 4.18 stable release since it hit linus master with commit id e2576c8bdfd462c34b8a46c0084e7c30b0851bf4 ?

Thanks,
Neil

> ---
>  drivers/clk/meson/gxbb.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
> index 9309cfaaa464..4ada9668fd49 100644
> --- a/drivers/clk/meson/gxbb.c
> +++ b/drivers/clk/meson/gxbb.c
> @@ -506,6 +506,18 @@ static struct clk_regmap gxbb_fclk_div3 = {
>  		.ops = &clk_regmap_gate_ops,
>  		.parent_names = (const char *[]){ "fclk_div3_div" },
>  		.num_parents = 1,
> +		/*
> +		 * FIXME:
> +		 * This clock, as fdiv2, is used by the SCPI FW and is required
> +		 * by the platform to operate correctly.
> +		 * Until the following condition are met, we need this clock to
> +		 * be marked as critical:
> +		 * a) The SCPI generic driver claims and enable all the clocks
> +		 *    it needs
> +		 * b) CCF has a clock hand-off mechanism to make the sure the
> +		 *    clock stays on until the proper driver comes along
> +		 */
> +		.flags = CLK_IS_CRITICAL,
>  	},
>  };
>  
>