linux-kernel - Re: [PATCH v3] PM / devfreq: rk3399_dmc: Fix kernel oops when rockchip,pmu is absent

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Date:   Wed, 1 Jul 2020 11:04:43 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Marc Zyngier <maz@...nel.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Heiko Stuebner <heiko@...ech.de>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] PM / devfreq: rk3399_dmc: Fix kernel oops when
 rockchip,pmu is absent

Hi Marc,

On 6/30/20 7:05 PM, Marc Zyngier wrote:
> Booting a recent kernel on a rk3399-based system (nanopc-t4),
> equipped with a recent u-boot and ATF results in an Oops due
> to a NULL pointer dereference.
> 
> This turns out to be due to the rk3399-dmc driver looking for
> an *undocumented* property (rockchip,pmu), and happily using
> a NULL pointer when the property isn't there.
> 
> Instead, make most of what was brought in with 9173c5ceb035
> ("PM / devfreq: rk3399_dmc: Pass ODT and auto power down parameters
> to TF-A.") conditioned on finding this property in the device-tree,
> preventing the driver from exploding.
> 
> Cc: stable@...r.kernel.org
> Fixes: 9173c5ceb035 ("PM / devfreq: rk3399_dmc: Pass ODT and auto power down parameters to TF-A.")
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
> * From v2:
>   - Trimmed down commit message
>   - Cc stable
> 
>  drivers/devfreq/rk3399_dmc.c | 42 ++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/devfreq/rk3399_dmc.c b/drivers/devfreq/rk3399_dmc.c
> index 24f04f78285b..027769e39f9b 100644
> --- a/drivers/devfreq/rk3399_dmc.c
> +++ b/drivers/devfreq/rk3399_dmc.c
> @@ -95,18 +95,20 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
>  
>  	mutex_lock(&dmcfreq->lock);
>  
> -	if (target_rate >= dmcfreq->odt_dis_freq)
> -		odt_enable = true;
> -
> -	/*
> -	 * This makes a SMC call to the TF-A to set the DDR PD (power-down)
> -	 * timings and to enable or disable the ODT (on-die termination)
> -	 * resistors.
> -	 */
> -	arm_smccc_smc(ROCKCHIP_SIP_DRAM_FREQ, dmcfreq->odt_pd_arg0,
> -		      dmcfreq->odt_pd_arg1,
> -		      ROCKCHIP_SIP_CONFIG_DRAM_SET_ODT_PD,
> -		      odt_enable, 0, 0, 0, &res);
> +	if (dmcfreq->regmap_pmu) {
> +		if (target_rate >= dmcfreq->odt_dis_freq)
> +			odt_enable = true;
> +
> +		/*
> +		 * This makes a SMC call to the TF-A to set the DDR PD
> +		 * (power-down) timings and to enable or disable the
> +		 * ODT (on-die termination) resistors.
> +		 */
> +		arm_smccc_smc(ROCKCHIP_SIP_DRAM_FREQ, dmcfreq->odt_pd_arg0,
> +			      dmcfreq->odt_pd_arg1,
> +			      ROCKCHIP_SIP_CONFIG_DRAM_SET_ODT_PD,
> +			      odt_enable, 0, 0, 0, &res);
> +	}
>  
>  	/*
>  	 * If frequency scaling from low to high, adjust voltage first.
> @@ -371,13 +373,14 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev)
>  	}
>  
>  	node = of_parse_phandle(np, "rockchip,pmu", 0);
> -	if (node) {
> -		data->regmap_pmu = syscon_node_to_regmap(node);
> -		of_node_put(node);
> -		if (IS_ERR(data->regmap_pmu)) {
> -			ret = PTR_ERR(data->regmap_pmu);
> -			goto err_edev;
> -		}
> +	if (!node)
> +		goto no_pmu;
> +
> +	data->regmap_pmu = syscon_node_to_regmap(node);
> +	of_node_put(node);
> +	if (IS_ERR(data->regmap_pmu)) {
> +		ret = PTR_ERR(data->regmap_pmu);
> +		goto err_edev;
>  	}
>  
>  	regmap_read(data->regmap_pmu, RK3399_PMUGRF_OS_REG2, &val);
> @@ -399,6 +402,7 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev)
>  		goto err_edev;
>  	};
>  
> +no_pmu:
>  	arm_smccc_smc(ROCKCHIP_SIP_DRAM_FREQ, 0, 0,
>  		      ROCKCHIP_SIP_CONFIG_DRAM_INIT,
>  		      0, 0, 0, 0, &res);
> 

Applied it. Thanks.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics