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Tue, 13 Aug 2024 12:06:46 +0000 (GMT) Received: from nasanex01a.na.qualcomm.com (nasanex01a.na.qualcomm.com [10.52.223.231]) by NASANPPMTA03.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 47DC6jtp027343 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 13 Aug 2024 12:06:45 GMT Received: from [10.133.1.196] (10.80.80.8) by nasanex01a.na.qualcomm.com (10.52.223.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Tue, 13 Aug 2024 05:06:42 -0700 Message-ID: <3cb1da06-88e3-4dd2-b56c-e0ab725ef6b2@quicinc.com> Date: Tue, 13 Aug 2024 15:06:23 +0300 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] iommu/arm-smmu-qcom: remove runtime pm enabling for TBU driver To: Zhenhua Huang , Pranjal Shrivastava CC: , , , , , , , , , Georgi Djakov References: <1722335443-30080-1-git-send-email-quic_zhenhuah@quicinc.com> Content-Language: en-US From: Georgi Djakov In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nasanex01a.na.qualcomm.com (10.52.223.231) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: 33E62etIps3z33ArWAoTcMfQb0k2iyOH X-Proofpoint-ORIG-GUID: 33E62etIps3z33ArWAoTcMfQb0k2iyOH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-13_04,2024-08-13_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxlogscore=710 suspectscore=0 phishscore=0 malwarescore=0 mlxscore=0 spamscore=0 lowpriorityscore=0 impostorscore=0 clxscore=1011 priorityscore=1501 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408130088 Hi Zhenhua, On 8/13/2024 10:56 AM, Zhenhua Huang wrote: > > On 2024/8/13 15:20, Pranjal Shrivastava wrote: >> On Tue, Aug 13, 2024 at 10:37:33AM +0800, Zhenhua Huang wrote: >>> >>> 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 [..] >> I agree that there are no pm_runtime_suspend/resume calls within the TBU >> driver. I'm just trying to understand why was pm_runtime enabled here >> earlier (since it's not implemented) in order to ensure that removing it >> doesn't cause further troubles? > > See above my assumption, need Georgi to comment but. Thank you for looking at the code! Your assumptions are mostly correct, but if you try this patch on a real sdm845 device you will notice some issues. So it's actually needed to re-configure the power-domains, three of which (MMNOC GDSCs) are requiring this because of a HW bug. I should have put a comment in the code to avoid confusion, but it took me some time to confirm it. I have sent a patch to handle this more cleanly: https://lore.kernel.org/lkml/20240813120015.3242787-1-quic_c_gdjako@quicinc.com So we should not remove the runtime pm calls until some version of the above patch gets merged. Thanks, Georgi >> I see Georgi added it as a part of >> https://lore.kernel.org/all/20240704010759.507798-1-quic_c_gdjako@quicinc.com/ >> >> But I'm unsure why was it required to fix that bug? > > I'm just thinking it is dead code and want to see if my understanding is correct.