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

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Date:   Mon, 5 Nov 2018 17:44:22 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Christian Hewitt <christianshewitt@...il.com>,
        Jerome Brunet <jbrunet@...libre.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: meson-gxbb: set fclk_div3 as CLK_IS_CRITICAL

On 16/10/2018 06:54, Christian Hewitt wrote:
> On 15 Oct 2018, at 9:07 pm, Jerome Brunet <jbrunet@...libre.com> wrote:
>>
>> On Sat, 2018-10-13 at 18:08 +0200, Michael Turquette wrote:
>>> Quoting Christian Hewitt (2018-10-13 12:04:46)
>>>> 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.
>>>>
>>>> Bisect gives 'commit 05f814402d6174369b3b29832cbb5eb5ed287059 ("clk:
>>>> meson: add fdiv clock gates") between 4.16 and 4.16-rc1 as the first
>>>> bad commit. This added support for the missing clock gates before the
>>>> fixed PLL fixed dividers (FCLK_DIVx) and the clock framework which
>>>> disabled all the unused fixed dividers, thus it disabled a critical
>>>> clock path for the SCPI Co-Processor.
>>>>
>>>> This change simply sets the FCLK_DIV3 gate as critical to ensure
>>>> nothing can disable it.
>>>

[...]

>>
>> Christian, is Ok if I amend your patch, or do you prefer to post a v2 ?
>> Mike, with explained, is this change OK with you ?
> 
> I’m happy for you to amend, it’s easier for me.
> Christian

Gentle ping, could this go into 4.20 fixes ?

Thanks,
Neil

> 
>>>
>>> Regards,
>>> Mike
>>>
>>>>
>>>> Signed-off-by: Christian Hewitt <christianshewitt@...il.com>
>>>> ---
>>>> drivers/clk/meson/gxbb.c | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
>>>> index 86d3ae5..4c8925d 100644
>>>> --- a/drivers/clk/meson/gxbb.c
>>>> +++ b/drivers/clk/meson/gxbb.c
>>>> @@ -509,6 +509,7 @@ static struct clk_fixed_factor gxbb_fclk_div3_div = {
>>>>                .ops = &clk_fixed_factor_ops,
>>>>                .parent_names = (const char *[]){ "fixed_pll" },
>>>>                .num_parents = 1,
>>>> +               .flags = CLK_IS_CRITICAL,
>>>>        },
>>>> };
>>>>
>>>> -- 
>>>> 2.7.4
>