Re: [PATCH v2] firmware: qcom: scm: Fix incorrect of_node_put call in scm_init

From: Jerome Forissier <jerome.forissier@linaro.org>
To: Stephen Boyd <sboyd@codeaurora.org>,
	Loys Ollivier <lollivier@baylibre.com>
Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
	David Brown <david.brown@linaro.org>,
	Andy Gross <andy.gross@linaro.org>,
	linux-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Jerome Brunet <jbrunet@baylibre.com>,
	Jens Wiklander <jens.wiklander@linaro.org>
Subject: Re: [PATCH v2] firmware: qcom: scm: Fix incorrect of_node_put call in scm_init
Date: Thu, 7 Dec 2017 09:42:11 +0100	[thread overview]
Message-ID: <40113581-4b8c-defe-ba90-0aabc30a1b6d@linaro.org> (raw)
In-Reply-To: <20171206200601.GH4283@codeaurora.org>


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@baylibre.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;
>  
>