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b=CKLdjjcFAcrHX8Tu4W0AUGGx6ASqOj60q00gW/y9Lu1i2RkB3UDDt2EIBwyAfkF9eZiZhkX6zUcU8Pehq6qjY9hOrs9savBVwyuIrqT6jstQy7nxyjN/xAOo/dFk4nm9iv48RVMBqjjug+fOgSSGvtthkv3KqONGmgZaoVIRJZc= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DS7PR12MB9501.namprd12.prod.outlook.com (2603:10b6:8:250::17) by SA1PR12MB6725.namprd12.prod.outlook.com (2603:10b6:806:254::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9745.12; Fri, 20 Mar 2026 15:38:58 +0000 Received: from DS7PR12MB9501.namprd12.prod.outlook.com ([fe80::4564:457c:524b:6b96]) by DS7PR12MB9501.namprd12.prod.outlook.com ([fe80::4564:457c:524b:6b96%4]) with mapi id 15.20.9723.014; Fri, 20 Mar 2026 15:38:57 +0000 Message-ID: <4268191f-2063-4031-8c67-3663cc7c5d66@amd.com> Date: Fri, 20 Mar 2026 11:38:54 -0400 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] i2c: designware: amdisp: Fix null pointer dereference in runtime resume To: Andy Shevchenko Cc: Mario Limonciello , Pratap Nirujogi , andi.shyti@kernel.org, mika.westerberg@linux.intel.com, jsd@semihalf.com, rafael.j.wysocki@intel.com, mlimonci@amd.com, benjamin.chan@amd.com, bin.du@amd.com, king.li@amd.com, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260309220038.1420996-1-pratap.nirujogi@amd.com> <4527c72d-bc59-4f5d-af94-4b2f37d75a96@amd.com> <61dbe8a1-6578-4690-8571-6b00c1850d34@amd.com> Content-Language: en-GB From: "Nirujogi, Pratap" In-Reply-To: Content-Type: text/plain; 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Use proper caution when opening attachments, clicking links, or responding. > > > On Thu, Mar 19, 2026 at 05:09:55PM -0400, Nirujogi, Pratap wrote: >> On 3/9/2026 9:29 PM, Mario Limonciello wrote: >>> On 3/9/2026 5:00 PM, Pratap Nirujogi wrote: > > ... > >>>> Fixes: 02c057ddefef ("ACPI: video: Convert the driver to a platform one") >>> >>> Is this the right commit that introduced the race? Did it change the >>> timing? >>> >>> Or was the race always there and we just got lucky until that commit >>> went in? >>> >> My apologies for mixing up this change along with other changes that were >> needed to fix the AMD ISP driver regressions in v7.0. >> >> I investigated further and found that this issue was exposed by the below >> commit. >> >> https://github.com/torvalds/linux/commit/38fa29b01a6a295aedb69d1bbdad70acd7d204c6 > > Still it might be not a culprit as at that point the device should be in power > on state. > >> However, the resume‑probe race condition existed even earlier and had not >> surfaced because device initialization in resume is done only when init >> handle is valid. > > That's what the initial cause, the AMD ISP driver initially relies on > the broken (racy) behaviour. So, the original patch d6263c468a761 does not > explain that bit. You need to go deeper and understand why the heck that > condition is present there. > >> Here is some background and context on this change: > > Exactly, the below seems that you have nailed it down. > >> The amdisp i2c device requires ISP to be in power on state for probe to >> succeed. To meet this requirement, we added this device, which is a amdgpu >> MFD child to the genpd, to control isp power using runtime PM. The >> pm_runtime_get_sync() call before probe triggers a PM resume, which powers >> on the ISP and also invokes the amdisp i2c runtime resume before the probe >> completes resulting in this race condition. >> >> To fix this issue properly, I’m considering this change. Please review and >> share your feedback on whether this makes sense. >> >> - Call dev_pm_genpd_resume() to Power ON ISP before probe >> - Call dev_pm_genpd_suspend() to Power OFF ISP after probe >> - Call pm_runtime_enable() after probe is successful to take care of system >> suspend/resume. > > I don't know the scope of dev_pm_genpd_*() usage, but the description of > the proposed change sounds sane. And definitely it's much much better than > previous attempt. > Thanks, Andy, for the feedback and comments. I’ll send out v2 with the proposed changes. Thanks, Pratap > -- > With Best Regards, > Andy Shevchenko > >