linux-kernel - Re: [PATCH] clk: imx8mq: Mark AHB clock as critical

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Message-ID: <20190803072723.GB7597@X250>
Date:   Sat, 3 Aug 2019 09:27:25 +0200
From:   Shawn Guo <shawnguo@...nel.org>
To:     Daniel Baluta <daniel.baluta@...il.com>
Cc:     Stephen Boyd <sboyd@...nel.org>, Abel Vesa <abel.vesa@....com>,
        Anson Huang <anson.huang@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Mike Turquette <mturquette@...libre.com>,
        Sascha Hauer <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: imx8mq: Mark AHB clock as critical

On Sat, Jul 27, 2019 at 09:30:57AM +0300, Daniel Baluta wrote:
> On Tue, Jul 23, 2019 at 6:17 AM Stephen Boyd <sboyd@...nel.org> wrote:
> >
> > Quoting Abel Vesa (2019-07-05 01:52:19)
> > > On 19-06-25 15:32:22, Stephen Boyd wrote:
> > > > Quoting Abel Vesa (2019-06-25 02:01:56)
> > > > > Keep the AHB clock always on since there is no driver to control it and
> > > > > all the other clocks that use it as parent rely on it being always enabled.
> > > > >
> > > > > Signed-off-by: Abel Vesa <abel.vesa@....com>
> > > > > ---
> > > > >  drivers/clk/imx/clk-imx8mq.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/clk/imx/clk-imx8mq.c b/drivers/clk/imx/clk-imx8mq.c
> > > > > index 5fbc2a7..b48268b 100644
> > > > > --- a/drivers/clk/imx/clk-imx8mq.c
> > > > > +++ b/drivers/clk/imx/clk-imx8mq.c
> > > > > @@ -398,7 +398,7 @@ static int imx8mq_clocks_probe(struct platform_device *pdev)
> > > > >         clks[IMX8MQ_CLK_NOC_APB] = imx8m_clk_composite_critical("noc_apb", imx8mq_noc_apb_sels, base + 0x8d80);
> > > > >
> > > > >         /* AHB */
> > > > > -       clks[IMX8MQ_CLK_AHB] = imx8m_clk_composite("ahb", imx8mq_ahb_sels, base + 0x9000);
> > > > > +       clks[IMX8MQ_CLK_AHB] = imx8m_clk_composite_critical("ahb", imx8mq_ahb_sels, base + 0x9000);
> > > >
> > > > Please add a comment into the code why it's critical.
> > >
> > > Comment explaining why the AHB bus clock is critical ?
> > > Isn't that self-explanatory ?
> >
> > Nope, it isn't self-explanatory, because nothing on this line says "bus"
> > and it could be that someone reading this code isn't well versed in the
> > concepts of ARM world AHB to connect the two.
> 
> Agree with Stephen. Commit message should try to give as much details
> as possible
> also maybe educate the readers who might not have that much knowledge.
> 
> Abel, I understand that for someone who works daily with this part of the kernel
> this change might look trivial.
> 
> Also, without this patch linux-next hangs on imx8mq.

How does that happen?  Mainline is fine there?

Shawn