linux-kernel - Re: [PATCH] clk: at91: fix possible dead lock in new drivers

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Date:   Fri, 3 Jul 2020 10:58:55 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc:     Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Stephen Boyd <sboyd@...nel.org>, kernel@...gutronix.de,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: at91: fix possible dead lock in new drivers

On 03/07/2020 09:32:35+0200, Ahmad Fatoum wrote:
> syscon_node_to_regmap() will make the created regmap get and enable the
> first clock it can parse from the device tree. This clock is not needed to
> access the registers and should not be enabled at that time.
> 
> Use device_node_to_regmap to resolve this as it looks up the regmap in
> the same list but doesn't care about the clocks. This issue is detected
> by lockdep when booting the sama5d3 with a device tree containing the
> new clk bindings.
> 
> This fix already happened in 6956eb33abb5 ("clk: at91: fix possible
> deadlock") for the drivers that had been migrated to the new clk binding
> back then. This does the same for the new drivers as well.
> 
> Fixes: 01e2113de9a5 ("clk: at91: add sam9x60 pmc driver")
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
Acked-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

> ---
> Only boot tested on the sama5d3.
> ---
>  drivers/clk/at91/at91sam9g45.c | 2 +-
>  drivers/clk/at91/at91sam9n12.c | 2 +-
>  drivers/clk/at91/sam9x60.c     | 2 +-
>  drivers/clk/at91/sama5d3.c     | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/clk/at91/at91sam9g45.c b/drivers/clk/at91/at91sam9g45.c
> index 9873b583c260..fe9d391adeba 100644
> --- a/drivers/clk/at91/at91sam9g45.c
> +++ b/drivers/clk/at91/at91sam9g45.c
> @@ -111,7 +111,7 @@ static void __init at91sam9g45_pmc_setup(struct device_node *np)
>  		return;
>  	mainxtal_name = of_clk_get_parent_name(np, i);
>  
> -	regmap = syscon_node_to_regmap(np);
> +	regmap = device_node_to_regmap(np);
>  	if (IS_ERR(regmap))
>  		return;
>  
> diff --git a/drivers/clk/at91/at91sam9n12.c b/drivers/clk/at91/at91sam9n12.c
> index 630dc5d87171..4aa97e672bd6 100644
> --- a/drivers/clk/at91/at91sam9n12.c
> +++ b/drivers/clk/at91/at91sam9n12.c
> @@ -124,7 +124,7 @@ static void __init at91sam9n12_pmc_setup(struct device_node *np)
>  		return;
>  	mainxtal_name = of_clk_get_parent_name(np, i);
>  
> -	regmap = syscon_node_to_regmap(np);
> +	regmap = device_node_to_regmap(np);
>  	if (IS_ERR(regmap))
>  		return;
>  
> diff --git a/drivers/clk/at91/sam9x60.c b/drivers/clk/at91/sam9x60.c
> index 3e20aa68259f..2b4c67485eee 100644
> --- a/drivers/clk/at91/sam9x60.c
> +++ b/drivers/clk/at91/sam9x60.c
> @@ -178,7 +178,7 @@ static void __init sam9x60_pmc_setup(struct device_node *np)
>  		return;
>  	mainxtal_name = of_clk_get_parent_name(np, i);
>  
> -	regmap = syscon_node_to_regmap(np);
> +	regmap = device_node_to_regmap(np);
>  	if (IS_ERR(regmap))
>  		return;
>  
> diff --git a/drivers/clk/at91/sama5d3.c b/drivers/clk/at91/sama5d3.c
> index 5e4e44dd4c37..5609b04e6565 100644
> --- a/drivers/clk/at91/sama5d3.c
> +++ b/drivers/clk/at91/sama5d3.c
> @@ -121,7 +121,7 @@ static void __init sama5d3_pmc_setup(struct device_node *np)
>  		return;
>  	mainxtal_name = of_clk_get_parent_name(np, i);
>  
> -	regmap = syscon_node_to_regmap(np);
> +	regmap = device_node_to_regmap(np);
>  	if (IS_ERR(regmap))
>  		return;
>  
> -- 
> 2.27.0
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com