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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH V1] accel/amdxdna: Fix tail-pointer polling in mailbox_get_msg() Content-Language: en-US To: "Falkowski, Maciej" , , , CC: , , , References: <20251204181603.793824-1-lizhi.hou@amd.com> From: Lizhi Hou In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: None (SATLEXMB04.amd.com: lizhi.hou@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF000023D9:EE_|SJ2PR12MB8111:EE_ X-MS-Office365-Filtering-Correlation-Id: aaa558f6-bc4b-4ddf-3b33-08de3677a7a7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|376014|36860700013|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?b3VxZjlWZGR5ZzNyN24vaEg1TXZMQysrL2VhdlBlQ1lQVXBkVFNJUHYwS3g4?= =?utf-8?B?S0hxaGpqdjdsNjJwZEJidzZlRGxSdDk2Y3hXdlVCSndDVVVTQ1dndkpEeVJO?= =?utf-8?B?WHRCZ2Y1UWxXM0twTEhidGVKRWtXcEhHQ1M4NW9YUUc4Y3BVR1pFeEIvRHlv?= =?utf-8?B?aFRWWmxnb245a1B1N1BpN2hieU5PTEl0TmJoZkxzdVh3SFFPY1J5RUVDOEJs?= =?utf-8?B?THRXcHhoM01hc21SY2NKZ3ptelVVam01Tkpyclg5cVN6eVpUS0RtT3lOTytB?= =?utf-8?B?MncyY3ZzNytLZHBSWDdtNko1VnhhRjZsNlpVa3g5eisxbzEyd3IxS1Y3aUZx?= =?utf-8?B?RFQxMXEyc0NCYU8vdmtaVVdZZE9VKzBiQWFKblYzMlBwT0VuNFQvOVR5by8z?= =?utf-8?B?QUVnRFRjd2wrUXdKRzF0b05KR0pKekd0RTI3Y1Y2THlKeVFkNGY1aXR6NEc3?= =?utf-8?B?aFRHaWpBVzNMb0tER3lGb2lqVCtCR2JpeGwyOHY2QXNaYzgwcnU2eWtWTWlE?= =?utf-8?B?YTVnamlLWEhDWHloVVQ3WnRHWHhWVXczZUtwN2xndC9ON1cvVGtNQm9QMEp4?= =?utf-8?B?VEpBZnB3bnZGeU82VWg0ZWZzV3h4RU1oeGR1dzZtVTBqZXFkQjNFK080UlRk?= =?utf-8?B?ZXdyU1cyT3M4WGlIeG9GM09SN0NTZmpNeC9uQlFKRU1sdlBONXVkN0w3bVJR?= =?utf-8?B?RUdyaGFWbGdDTGlleFpiVU9vbTVtaG8vblZyazlVTk5RZHJ2QVo2Rkg2b2ZY?= =?utf-8?B?Szk5OVo3OUJRYW5ldy9wb3ByZElCTnZLZjIwKzQ1WVlOaVQ1SGRuSjUzdy9U?= =?utf-8?B?ekt3WkNMTFpHSXgwMDJhUTNCcnQ5K3l3QnhmazNqZE9iL1ZwTjlUK3ViTHZS?= =?utf-8?B?M25EbUIwWmN6ajQ1NXc5c2tNMVBnY2ZyQkhYbzJyNmZRSjkwbzRZY1Yza0Jz?= =?utf-8?B?MGRKYyszbXBrbmp6Y2tIMUI1UDFOa2ZWcWdaTWlKcVU1NFpZZG1JeFlhWmp6?= =?utf-8?B?Q045UjM4WDdpTEVNNUJKUFg0cnBXcHQzZm0yT3dmYjBTcjZFQk1ORzcxVVVP?= =?utf-8?B?QmdTbHVMaEN3ZCsyQ2NpQ2VFVjlpQldVWmdkN2YzQTRQTHlLTlFESzVGbHUy?= =?utf-8?B?RUREaWh2UmFUOWg2enljdElZVzQ1VzVocStxamNib0hDNzV3UWpoWUJSRmRR?= =?utf-8?B?cTg4SjFDNlFSa2RsSWJ6bUlxejZWOEtLMElwQThSQ1BiRk9kNFZWYldPaDlN?= =?utf-8?B?Qyt1bFVyUDlmQ0d3am9odmNjdWc4MGE4b2sxRFM1SUNjV2pFekdoTkt4aTAy?= =?utf-8?B?Q2syR0RtUmVPOXVLK3BBdEZCSVg0eHhTY2xqeUFwc0xGd1RKZGZGbFpXeVlC?= =?utf-8?B?YXdqb1FBRHlCdm5zM0ZBNnRLWEtOZkhqaXhOaWtJN1FIclg3dkYrdHNVR3Y5?= =?utf-8?B?TGxlZHlPUUVCcTIvWDdHalJtNnNhMXFWNFNqSm5abE5YZm9MeG1DcWdMalFN?= =?utf-8?B?c1BPK3Y0cTNpcjBlaUtjYUQySmpvYlkxL2ZYQzEwc1FqNkRKSFNwLzN2Yi9F?= =?utf-8?B?U1hyV0RaR0JoaVdoWmlkRTZ6dlFXem9pL0tycFE2TW1rSUFMTnh3UkpNY0tm?= =?utf-8?B?aFpvUXFjQk03Z3pzSzIrQWdITDFyRWxkS3BScVRIdWJ6NnlzQm1pWFJCSUZv?= =?utf-8?B?N3M1d0xGaHVwVGpxZGgybXFRUlhsU2t5RE9USGk3dnAyZlgvYTF5cWhzRE1W?= =?utf-8?B?K0xYNkdmbHk0RExyKzNEQ1ZvMy9wK1pxTzJHMEsvSnBLdFowWGVKL25TZHRz?= =?utf-8?B?U1RxWjRRaWJ1MTFVYjJIcngzN1hTOFJEUXNPeGlTZ25rc0wwS2ZBTXRCL3Bt?= =?utf-8?B?QWxkU05sbjRkTTE5NXhTZ1FXKy9XWnZUZ25RazZnVlVMTk5VWUFxRXVJQ09t?= =?utf-8?B?UHpqb3YxQmdKNWJHOWRYcnRvVDg2Z3RONFF2Y2taTitTZmVwWWMzQzVlLy84?= =?utf-8?B?RUU2MEpqSTNvdVM5MlR1NlhiSWdnVzc2VU1tL0V6RnNybDJTeXNsajBBM3Yx?= =?utf-8?B?OHdFWEtMd2txZDR0cEh5bUtEWitidzR6SFFyZyt2STRtVjhta3FkSmVJMlAr?= =?utf-8?Q?VSFA=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(376014)(36860700013)(7053199007);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Dec 2025 16:34:27.3620 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: aaa558f6-bc4b-4ddf-3b33-08de3677a7a7 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF000023D9.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8111 Applied to drm-misc-next On 12/5/25 08:41, Falkowski, Maciej wrote: > Reviewed-by: Maciej Falkowski > > On 12/4/2025 7:16 PM, Lizhi Hou wrote: >> In mailbox_get_msg(), mailbox_reg_read_non_zero() is called to poll >> for a >> non-zero tail pointer. This assumed that a zero value indicates an >> error. >> However, certain corner cases legitimately produce a zero tail pointer. >> To handle these cases, remove mailbox_reg_read_non_zero(). The zero tail >> pointer will be treated as a valid rewind event. >> >> Signed-off-by: Lizhi Hou >> --- >>   drivers/accel/amdxdna/amdxdna_mailbox.c | 19 +------------------ >>   1 file changed, 1 insertion(+), 18 deletions(-) >> >> diff --git a/drivers/accel/amdxdna/amdxdna_mailbox.c >> b/drivers/accel/amdxdna/amdxdna_mailbox.c >> index 858df97cd3fb..a60a85ce564c 100644 >> --- a/drivers/accel/amdxdna/amdxdna_mailbox.c >> +++ b/drivers/accel/amdxdna/amdxdna_mailbox.c >> @@ -112,22 +112,6 @@ static u32 mailbox_reg_read(struct >> mailbox_channel *mb_chann, u32 mbox_reg) >>       return readl(ringbuf_addr); >>   } >>   -static int mailbox_reg_read_non_zero(struct mailbox_channel >> *mb_chann, u32 mbox_reg, u32 *val) >> -{ >> -    struct xdna_mailbox_res *mb_res = &mb_chann->mb->res; >> -    void __iomem *ringbuf_addr = mb_res->mbox_base + mbox_reg; >> -    int ret, value; >> - >> -    /* Poll till value is not zero */ >> -    ret = readx_poll_timeout(readl, ringbuf_addr, value, >> -                 value, 1 /* us */, 100); >> -    if (ret < 0) >> -        return ret; >> - >> -    *val = value; >> -    return 0; >> -} >> - >>   static inline void >>   mailbox_set_headptr(struct mailbox_channel *mb_chann, u32 headptr_val) >>   { >> @@ -286,8 +270,7 @@ static int mailbox_get_msg(struct mailbox_channel >> *mb_chann) >>       u32 start_addr; >>       int ret; >>   -    if (mailbox_reg_read_non_zero(mb_chann, >> mb_chann->res[CHAN_RES_I2X].mb_tail_ptr_reg, &tail)) >> -        return -EINVAL; >> +    tail = mailbox_get_tailptr(mb_chann, CHAN_RES_I2X); >>       head = mb_chann->i2x_head; >>       ringbuf_size = mailbox_get_ringbuf_size(mb_chann, CHAN_RES_I2X); >>       start_addr = mb_chann->res[CHAN_RES_I2X].rb_start_addr;