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

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Date:   Tue, 12 Dec 2017 16:35:03 +0100
From:   Loys Ollivier <lollivier@...libre.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Jerome Forissier <jerome.forissier@...aro.org>,
        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 08/12/2017 18:04, Stephen Boyd wrote:
> On 12/07, Loys Ollivier wrote:
>>
>>
>> On 07/12/2017 09:42, Jerome Forissier wrote:
>>>
>>>
>>> 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
>>>
>> Well, the patch I sent is a fix for a specific bug I am encountering.
>> I tested the patch and it solves my problem. Stephen, your changes looks
>> good but it's a change in the driver's behavior. Maybe it could be
>> another patch ?
> 
> Sure. But there's another of_node_put(fw_np) in this function, so
> why isn't that also removed? Assuming of_find_matching_node() is
> calling of_node_put() on what's passed in, then the node is going
> to get put twice in the "working" case.
> 
> Andy?
>
Agreed, I had a look and this second call to of_node_put(fw_np) seem to
be unnecessary as well. Unfortunately I can't test your suggestion as I
am using another platform arch. I am just testing that this driver does
not break my arch.
I can submit a v3 removing this of_node_put as well if you want.