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Thu, 12 Mar 2026 20:31:22 +0000 Message-ID: Date: Thu, 12 Mar 2026 16:31:17 -0400 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] drm/amd/display: Fix uninitialized variable use which breaks full LTO To: Calvin Owens , linux-kernel@vger.kernel.org Cc: dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Charlene Liu , Ovidiu Bunea , Alex Hung , Dan Wheeler , Alex Deucher , Leo Li , Rodrigo Siqueira , Christian Koenig , David Airlie , Simona Vetter , llvm@lists.linux.dev References: Content-Language: en-US From: Harry Wentland In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: YQBPR01CA0126.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:1::26) To BN9PR12MB5130.namprd12.prod.outlook.com (2603:10b6:408:137::9) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN9PR12MB5130:EE_|SAWPR12MB999141:EE_ X-MS-Office365-Filtering-Correlation-Id: 9501644e-4558-4bf7-3257-08de8076535a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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But when > full LTO is enabled, it causes the compiler to "optimize" out huge > swaths of amdgpu initialization code, and the driver is unusable: > > amdgpu 0000:03:00.0: [drm] Loading DMUB firmware via PSP: version=0x07002F00 > amdgpu 0000:03:00.0: sw_init of IP block failed 5 > amdgpu 0000:03:00.0: amdgpu_device_ip_init failed > amdgpu 0000:03:00.0: Fatal error during GPU init > > It surprises me that neither gcc nor clang emit a warning about this: I > only found it by bisecting the LTO breakage. > > Fix by using the bss_data_size field from fw_meta_info_params, as was > presumably intended. > > Fixes: e1b385726f7f ("drm/amd/display: Add additional checks for PSP footer size") > Signed-off-by: Calvin Owens Reviewed-by: Harry Wentland Harry > --- > Changes in v2: > * Use fw_meta_info_params.bss_data_size instead of repeating the load > from the payload header field [Nathan] > > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > index b3d6f2cd8ab6..0d1c772ef713 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > @@ -2553,9 +2553,9 @@ static int dm_dmub_sw_init(struct amdgpu_device *adev) > fw_meta_info_params.bss_data_size = le32_to_cpu(hdr->bss_data_bytes); > fw_meta_info_params.fw_inst_const = adev->dm.dmub_fw->data + > le32_to_cpu(hdr->header.ucode_array_offset_bytes) + > PSP_HEADER_BYTES_256; > - fw_meta_info_params.fw_bss_data = region_params.bss_data_size ? adev->dm.dmub_fw->data + > + fw_meta_info_params.fw_bss_data = fw_meta_info_params.bss_data_size ? adev->dm.dmub_fw->data + > le32_to_cpu(hdr->header.ucode_array_offset_bytes) + > le32_to_cpu(hdr->inst_const_bytes) : NULL; > fw_meta_info_params.custom_psp_footer_size = 0; >