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Subject: Re: [PATCH] soc: mediatek: Check if power domains can be powered on
 at boot time
To:     Nicolas Boichat <drinkcat@chromium.org>
Cc:     Daniel Kurtz <djkurtz@chromium.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mediatek@lists.infradead.org
References: <20200730120054.1.I5e6f8c262031d0451fe7241b744f4f3111c1ce71@changeid>
From:   Matthias Brugger <matthias.bgg@gmail.com>
Message-ID: <6549429e-bd3c-5249-2fbd-cd1c45b5b2c1@gmail.com>
Date:   Mon, 21 Sep 2020 19:07:50 +0200
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Hi Nicolas,

Thanks for the patch.

On 30/07/2020 06:01, Nicolas Boichat wrote:
> In the error case, where a power domain cannot be powered on
> successfully at boot time (in mtk_register_power_domains),
> pm_genpd_init would still be called with is_off=false, and the
> system would later try to disable the power domain again, triggering
> warnings as disabled clocks are disabled again (and other potential
> issues).
> 
> Fixes: c84e358718a66f7 ("soc: Mediatek: Add SCPSYS power domain driver")
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> 
> ---
> 
>   drivers/soc/mediatek/mtk-scpsys.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> index f669d3754627dad..0055a52a49733d5 100644
> --- a/drivers/soc/mediatek/mtk-scpsys.c
> +++ b/drivers/soc/mediatek/mtk-scpsys.c
> @@ -524,6 +524,7 @@ static void mtk_register_power_domains(struct platform_device *pdev,
>   	for (i = 0; i < num; i++) {
>   		struct scp_domain *scpd = &scp->domains[i];
>   		struct generic_pm_domain *genpd = &scpd->genpd;
> +		bool on;
>   
>   		/*
>   		 * Initially turn on all domains to make the domains usable
> @@ -531,9 +532,9 @@ static void mtk_register_power_domains(struct platform_device *pdev,
>   		 * software.  The unused domains will be switched off during
>   		 * late_init time.
>   		 */
> -		genpd->power_on(genpd);
> +		on = genpd->power_on(genpd) >= 0;

Is this something we expect? On probing we realize that some domains can't be 
turned on?

I understand that this would be a bug in the driver. Therefore we should at most 
provide a warning instead of working around the bug, hiding it. Or do I got this 
wrong?

Regards,
Matthias

>   
> -		pm_genpd_init(genpd, NULL, false);
> +		pm_genpd_init(genpd, NULL, !on);
>   	}
>   
>   	/*
>