linux-kernel - Re: [PATCH v2] firmware: qcom: scm: Fix incorrect of_node_put call in scm

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Message-ID: <40113581-4b8c-defe-ba90-0aabc30a1b6d@linaro.org>
Date:   Thu, 7 Dec 2017 09:42:11 +0100
From:   Jerome Forissier <jerome.forissier@...aro.org>
To:     Stephen Boyd <sboyd@...eaurora.org>,
        Loys Ollivier <lollivier@...libre.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Brown <david.brown@...aro.org>,
        Andy Gross <andy.gross@...aro.org>, linux-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Jerome Brunet <jbrunet@...libre.com>,
        Jens Wiklander <jens.wiklander@...aro.org>
Subject: Re: [PATCH v2] firmware: qcom: scm: Fix incorrect of_node_put call in
 scm_init



On 12/06/2017 09:06 PM, Stephen Boyd wrote:
> On 12/06, Loys Ollivier wrote:
>> When using other platform architectures, in the init of the qcom_scm
>> driver, of_node_put is called on /firmware if no qcom dt is found.
>> This results in a kernel error: Bad of_node_put() on /firmware.
>>
>> The call to of_node_put from the qcom_scm init is unnecessary as
>> of_find_matching_node is calling it automatically.
>>
>> Remove this of_node_put().
>>
>> Fixes: d0f6fa7ba2d6 ("firmware: qcom: scm: Convert SCM to platform driver")
>> Signed-off-by: Loys Ollivier <lollivier@...libre.com>
>> ---
> 
> This still looks wrong. Especially if of_find_matching_node() is
> going to look for siblings of the /firmware node for the
> compatible string for scm device. Why do we check at all? Can't
> we just delete this and let of_platform_populate() take care of
> it? BTW, OP-TEE driver seems to have a similar problem.

https://lkml.org/lkml/2017/11/29/230
		
> 
> ---8<----
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index af4c75217ea6..440d8f796faa 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -626,23 +626,11 @@ static int __init qcom_scm_init(void)
>  	int ret;
>  
>  	fw_np = of_find_node_by_name(NULL, "firmware");
> -
>  	if (!fw_np)
> -		return -ENODEV;
> -
> -	np = of_find_matching_node(fw_np, qcom_scm_dt_match);
> -
> -	if (!np) {
> -		of_node_put(fw_np);
> -		return -ENODEV;
> -	}
> -
> -	of_node_put(np);
> +		return 0;
>  
>  	ret = of_platform_populate(fw_np, qcom_scm_dt_match, NULL, NULL);
> -
>  	of_node_put(fw_np);
> -
>  	if (ret)
>  		return ret;
>  
>