linux-kernel - Re: [PATCH 1/1] iommu/arm-smmu-qcom: remove runtime pm enabling for TBU driver

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Message-ID: <cca690c3-916e-43b6-b2a5-eca4f2eb838e@quicinc.com>
Date: Tue, 13 Aug 2024 10:37:33 +0800
From: Zhenhua Huang <quic_zhenhuah@...cinc.com>
To: Pranjal Shrivastava <praan@...gle.com>
CC: <robdclark@...il.com>, <will@...nel.org>, <robin.murphy@....com>,
        <joro@...tes.org>, <iommu@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <quic_c_gdjako@...cinc.com>, <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH 1/1] iommu/arm-smmu-qcom: remove runtime pm enabling for
 TBU driver



On 2024/8/12 21:25, Pranjal Shrivastava wrote:
> On Tue, Jul 30, 2024 at 06:30:43PM +0800, Zhenhua Huang wrote:
>> TBU driver has no runtime pm support now, adding pm_runtime_enable()
>> seems to be useless. Remove it.
>>
>> Signed-off-by: Zhenhua Huang <quic_zhenhuah@...cinc.com>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 6 ------
>>   1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> index 36c6b36ad4ff..aff2fe1fda13 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> @@ -566,7 +566,6 @@ static struct acpi_platform_list qcom_acpi_platlist[] = {
>>   
>>   static int qcom_smmu_tbu_probe(struct platform_device *pdev)
>>   {
>> -	struct device *dev = &pdev->dev;
>>   	int ret;
>>   
>>   	if (IS_ENABLED(CONFIG_ARM_SMMU_QCOM_DEBUG)) {
>> @@ -575,11 +574,6 @@ static int qcom_smmu_tbu_probe(struct platform_device *pdev)
>>   			return ret;
>>   	}
>>   
>> -	if (dev->pm_domain) {
>> -		pm_runtime_set_active(dev);
>> -		pm_runtime_enable(dev);
> 
> I assumed that this was required to avoid the TBU from being powered
> down? If so, then I think we shall move it under the

Hi Pranjal,

In my sense, this was giving the TBU ability to power down when 
necessary(through pm callbacks)? While I haven't seen any RPM impl for 
TBU device.. hence having the doubt..

Thanks,
Zhenhua

> previous if condition, i.e. CONFIG_ARM_SMMU_QCOM_DEBUG?
> 
> If not, we can remove it give that the TBU would be powered ON as needed
> 
>> -	}
>> -
>>   	return 0;
>>   }
>>   
>> -- 
>> 2.7.4
>>
>>
> 
> Thanks,
> Pranjal