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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?5aw76eEMyA1I2QM3xbamEHSnR8/ieXaP3NvigL2wStG8ksIXn2Jx9foKKs22?= =?us-ascii?Q?eJu3GqCwjiFartqEo4rTCzwWvzXnIPatvs2TjVDb7jM1VVAAEXY4CY9yXZgG?= =?us-ascii?Q?zPjAAppyp215q7O9QINBYjhHpT9j73ZdE8uusKZQUps1UZ9Guo34bYIDuWcA?= =?us-ascii?Q?fwQOz1/aZtFLimfPf8EU50EVldVpC7FAnBVKJHK3PYgM3mcDgHTZFHPOLito?= =?us-ascii?Q?fjD7PLm7nFVe2j8Wh8ic+dYPQwa/Fq1pVN26kLvFOg8NuK4D3m/NlYxnaPtg?= =?us-ascii?Q?jH07Dki5cWCanwTEGpGYikEcYfwaA5JrvemPw0wZmP0q98AeGHcxzQoIaD8p?= =?us-ascii?Q?SNakH63KjjAQLQhzgbKq/A2ChBmf1YVoQHp2PGSdls6O4HIissViBv760Ven?= =?us-ascii?Q?M2MYjz1OR8AGdFxjIwcywF0Ah0QmhVOrQQcLwoXWEfdP7y4hsGXG8ERuGmqo?= =?us-ascii?Q?DwYaGBiCHPDPdLpycy0BPSm7rwNYfmMRK+H/R+FyXhB5AOMoO4xUNDmtDwow?= =?us-ascii?Q?hMn6AjfrukRCO5/T3kG4j0FyU00Js8XzyMgvYe5WN5ax+QS25mbxzzE5gAUh?= =?us-ascii?Q?36y3UCITe+S960Ng52juYLWpcf5dW19VFwLj4EmQFy0Wgi+b1GXXDFwS4Jr1?= =?us-ascii?Q?ZHPeGRD5miHinDg968P+x+FRXIrlMkm4RFv+U/uPb9nVXjf5+Iow5JT2/Rp1?= =?us-ascii?Q?P21DEmwPXkE4aC0Oq+d0W7oXJoPd3aNpKkiyePEZy0eJdockpct+oFN/prKp?= =?us-ascii?Q?V9U5h2JLfYUI+2pdfxS4WvZZXr0R7k0iMgf7m2Z/YkTO/7MVjczvNMIf+qUm?= =?us-ascii?Q?iTp/dP/NvqriyxQ+1teourZQFw6qGlPugYcYdka6PCieugvAIBarwNJHcCZ8?= =?us-ascii?Q?aBjPomld04qoqs/oyaT5nhl+6X8s5Sr891CyTlX6imcjQEXlouySZF32qQK2?= =?us-ascii?Q?cLixyjDfXvcVqYss5HnV9BW13cWuErzhK578bjqTwq99H1BgebprEz/Zqsvl?= =?us-ascii?Q?0Vs8R4pUVxEhdaWx4U+3npersrl+YCCM/ZjWl0Y+NYaz62+qATyeMHWEbcbB?= =?us-ascii?Q?7AEZ1q1G9Q3ikTHDHQL8A6tknErX59I6AaCXi43njaglmYMqhdIo0LFXco0d?= =?us-ascii?Q?9ezX9uLroOEaFwOCpjgD1FVuW/7fjs+nWnoqilVBnQLtwrmfvlnxImGTjCUe?= =?us-ascii?Q?fkr4QtkxcVAGygvIfqHWLi6r8b1Xfi69Jo1Jo7YSZL4dQz5gbUpB+74RQxGs?= =?us-ascii?Q?b/SuxuhyveMsLhfREaJPbRQ8kXBPkmAEUaAEWhA4SJPyMobdeN2qx2RjDUCp?= =?us-ascii?Q?lRnAGhb1Tji9m6ikNXNT3tmWH3w95poQ5TCtZthMqAyWn0PQZ1UydTSpSJQ4?= =?us-ascii?Q?OKsbqeiuxut+FgkXvNzaCUY2PG01+sG1/WV4eGo6o/WmeNDpLAS0793HXJk7?= =?us-ascii?Q?uyGOX9UklXmjKdRcVu1uLweZ3O0JpJfQFUDtIF0GJPUmzKgfGGQL3LTL0L1a?= =?us-ascii?Q?t3xdQENCMzZWcsX6fwZQq1E5j2l6F6SmhwSAQweoUY8Yd5B8jmkZFI4+z93f?= =?us-ascii?Q?gCdomNwYGDgosux/xi1Blt88rJFvsBHrYK2JNle79A8Sve9mjZyJNYHgqFyq?= =?us-ascii?Q?KgAHl7D128nf4VB36md9e9tW1iToO0XVuRvDoDqUolcyGaObBUqnHrs6O4Ss?= =?us-ascii?Q?vjsTPuiAsPoXD3yx3xhug0U0TDbmlgwYm7ZAnngiQ9bLrxCyyFuCFytgX39X?= =?us-ascii?Q?58iDm1KzKw=3D=3D?= X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: c6080461-a358-4a3a-c20b-08de74b15cd3 X-MS-Exchange-CrossTenant-AuthSource: PA4PR04MB9366.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Feb 2026 21:03:45.0302 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: vE8y/0ixBRDCkyWY7AOrrH5dl0UtlpGBj5shQtkaEK0xwlbpeOdm2/Ls9ZQcZhiScVBxmEOgIq5LEc6Az5lJsQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PA4PR04MB9687 On Tue, Feb 24, 2026 at 10:34:55PM +0900, Koichiro Den wrote: > ntb_epf_peer_db_set() uses ffs(db_bits) to select a doorbell to ring. > ffs() returns a 1-based bit index (bit 0 -> 1). > > Entry 0 is reserved for link events, so doorbell bit 0 must map to entry > 1. However, since the initial commit 812ce2f8d14e ("NTB: Add support for > EPF PCI Non-Transparent Bridge"), the implementation has been adding an > extra +1, ending up using entry 2 for bit 0. Fixing the extra increment > would break interoperability with peers running older kernels. > > Keep the legacy behavior and document the offset and the resulting slot > layout to avoid confusion when enabling per-db-vector handling. > > Signed-off-by: Koichiro Den > --- Reviewed-by: Frank Li > drivers/ntb/hw/epf/ntb_hw_epf.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c > index d3ecf25a5162..bce7130fec39 100644 > --- a/drivers/ntb/hw/epf/ntb_hw_epf.c > +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c > @@ -43,6 +43,18 @@ > #define NTB_EPF_DB_DATA(n) (0x34 + (n) * 4) > #define NTB_EPF_DB_OFFSET(n) (0xB4 + (n) * 4) > > +/* > + * Legacy doorbell slot layout when paired with pci-epf-*ntb: > + * > + * slot 0 : reserved for link events > + * slot 1 : unused (historical extra offset) > + * slot 2 : DB#0 > + * slot 3 : DB#1 > + * ... > + * > + * Thus, NTB_EPF_MIN_DB_COUNT=3 means that we at least create vectors for > + * doorbells DB#0 and DB#1. > + */ > #define NTB_EPF_MIN_DB_COUNT 3 > #define NTB_EPF_MAX_DB_COUNT 31 > > @@ -473,6 +485,14 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx, > static int ntb_epf_peer_db_set(struct ntb_dev *ntb, u64 db_bits) > { > struct ntb_epf_dev *ndev = ntb_ndev(ntb); > + /* > + * ffs() returns a 1-based bit index (bit 0 -> 1). > + * > + * With slot 0 reserved for link events, DB#0 would naturally map to > + * slot 1. Historically an extra +1 offset was added, so DB#0 maps to > + * slot 2 and slot 1 remains unused. Keep this mapping for > + * backward-compatibility. > + */ > u32 interrupt_num = ffs(db_bits) + 1; > struct device *dev = ndev->dev; > u32 db_entry_size; > -- > 2.51.0 >