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

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Date:   Mon, 22 Jul 2019 14:25:36 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Abel Vesa <abel.vesa@....com>
Cc:     Anson Huang <anson.huang@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Mike Turquette <mturquette@...libre.com>,
        Sascha Hauer <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        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

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.

> 
> > 
> > >         clks[IMX8MQ_CLK_AUDIO_AHB] = imx8m_clk_composite("audio_ahb", imx8mq_audio_ahb_sels, base + 0x9100);