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dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB9174.namprd12.prod.outlook.com (2603:10b6:510:2ed::9) by SN7PR12MB7810.namprd12.prod.outlook.com (2603:10b6:806:34c::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.615.13; Sun, 15 Nov 2026 14:16:22 +0000 Received: from PH7PR12MB9174.namprd12.prod.outlook.com ([fe80::eaaa:b430:ba9:5dc]) by PH7PR12MB9174.namprd12.prod.outlook.com ([fe80::eaaa:b430:ba9:5dc%7]) with mapi id 15.21.0615.012; Sun, 15 Nov 2026 14:16:22 +0000 Message-ID: <404553c5-60b3-464a-8d76-7850120f3d58@amd.com> Date: Sun, 15 Nov 2026 08:16:20 -0600 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] platform/x86/amd: hfi: Stand down when amd-pstate CAS is active Content-Language: en-US To: Vishal Badole , ray.huang@amd.com, rafael@kernel.org, viresh.kumar@linaro.org, perry.yuan@amd.com, kprateek.nayak@amd.com, hansg@kernel.org, ilpo.jarvinen@linux.intel.com, platform-driver-x86@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Krishnamoorthi M References: <20261114150310.1377654-1-Vishal.Badole@amd.com> <20261114150310.1377654-3-Vishal.Badole@amd.com> From: Mario Limonciello In-Reply-To: <20261114150310.1377654-3-Vishal.Badole@amd.com> Content-Type: text/plain; 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Running both simultaneously would cause them to overwrite > each other's settings, leading to unpredictable task placement on hybrid > platforms. > > Avoid loading amd-hfi if CAS is enabled. > > Signed-off-by: Krishnamoorthi M When a patch is authored by another person and you send it on their behalf you need to add your own S-o-b as well. Think of it like a chain of custody. > --- > drivers/platform/x86/amd/hfi/hfi.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/platform/x86/amd/hfi/hfi.c b/drivers/platform/x86/amd/hfi/hfi.c > index 86a7f4332c35..b6878614e2bc 100644 > --- a/drivers/platform/x86/amd/hfi/hfi.c > +++ b/drivers/platform/x86/amd/hfi/hfi.c > @@ -29,6 +29,8 @@ > > #include > > +#include > + > #include > #include > > @@ -536,6 +538,12 @@ static int __init amd_hfi_init(void) > !cpu_feature_enabled(X86_FEATURE_AMD_WORKLOAD_CLASS)) > return -ENODEV; > > + /* amd-pstate CAS owns heterogeneous core scheduling when enabled. */ > + if (amd_pstate_cas_active()) { > + pr_debug("amd-pstate CAS is active, not loading amd-hfi\n"); > + return -ENODEV; > + } > + > ret = platform_driver_register(&amd_hfi_driver); > if (ret) > pr_err("failed to register HFI driver\n");