linux-kernel - Re: [PATCH] venus: core: add shutdown callback for venus

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Date:   Thu, 06 Aug 2020 09:17:30 +0530
From:   mansur@...eaurora.org
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     stanimir.varbanov@...aro.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, vgarodia@...eaurora.org,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH] venus: core: add shutdown callback for venus

Hi Sai,

> On 2020-06-24 12:17, Sai Prakash Ranjan wrote:
>> Hi Mansur,
>> 
>> On 2020-06-13 16:03, Mansur Alisha Shaik wrote:
>>> After the SMMU translation is disabled in the
>>> arm-smmu shutdown callback during reboot, if
>>> any subsystem are still alive then IOVAs they
>>> are using will become PAs on bus, which may
>>> lead to crash.
>>> 
>>> Below are the consumers of smmu from venus
>>> arm-smmu: consumer: aa00000.video-codec supplier=15000000.iommu
>>> arm-smmu: consumer: video-firmware.0 supplier=15000000.iommu
>>> 
>>> So implemented shutdown callback, which detach iommu maps.
>>> 
>>> Change-Id: I0f0f331056e0b84b92f1d86f66618d4b1caaa24a
>>> Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
>>> ---
>>>  drivers/media/platform/qcom/venus/core.c | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
>>> 
>>> diff --git a/drivers/media/platform/qcom/venus/core.c
>>> b/drivers/media/platform/qcom/venus/core.c
>>> index 30d4b9e..acf798c 100644
>>> --- a/drivers/media/platform/qcom/venus/core.c
>>> +++ b/drivers/media/platform/qcom/venus/core.c
>>> @@ -371,6 +371,14 @@ static int venus_remove(struct platform_device 
>>> *pdev)
>>>  	return ret;
>>>  }
>>> 
>>> +static void venus_core_shutdown(struct platform_device *pdev)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = venus_remove(pdev);
>>> +	WARN_ON(ret < 0);
>> 
>> I don't think you should warn here, its shutdown path and you can't
>> do anything with this WARN unlike remove callback where you have
>> to be sure to cleanup properly so that you are able to reload module.
>> But if you still want a hint about this failure, then just add a 
>> dev_err()
>> to indicate the failure instead of a big stack trace spamming kernel 
>> log.
>> 

posted V2 version by adding dev_warn during shutdown failure instead of 
WARN_ON.
V2 version : https://lore.kernel.org/patchwork/patch/1284693/

>> Thanks,
>> Sai

---
Thanks,
Mansur