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Wed, 22 Apr 2026 12:09:35 +0200 From: Paul Geurts To: , , , , CC: , Paul Geurts Subject: [PATCH] NFC: trf7970a: Ignore antenna noise when checking for RF field Date: Wed, 22 Apr 2026 12:09:30 +0200 Message-ID: <20260422100930.581237-1-paul.geurts@prodrive-technologies.com> X-Mailer: git-send-email 2.39.2 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AMS0EPF000001B0:EE_|VI2PR02MB10999:EE_ X-MS-Office365-Filtering-Correlation-Id: b05fa4d7-3d42-4b82-14c5-08dea05741e0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700016|376014|82310400026|18002099003|56012099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:212.61.153.67;CTRY:NL;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:webmail.prodrive.nl;PTR:mail.prodrive-technologies.com;CAT:NONE;SFS:(13230040)(1800799024)(36860700016)(376014)(82310400026)(18002099003)(56012099003);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: yessdqGPVb1BjY2ugm8Mm8RI6FXwjq19Gga9qUxEvP+PZ6OUb3oNYsXnrK4KmH5UsrHCpErWW2WZuoqCp1ZufLqx2vB0pSzBm4q1PoDbr13hU9Jm26uQf0WKQU4b8mWTIWFJKfBeNuF1EKrTufUYI2b1v1N1HYkZuqvPn3RlzV112/rrcU/PFiWiRllOhAKX7UFVK27RNyrDyB21kNczYCTzKT2epAzZSPyEnalf1E2xtIlU3hmliRcYAeQEvoQyyU4VcdoVI6aUNyw88YJvqigVJfUBTsWh9B0x7kZ/IMdTnuno7qPlOqzp2S7WuDjRX0YNUpAkFChPChSKsvvuJls1eoY2KGMp4LoMIyjoOi6Gsy5y4LYIhM3GvZ/s7gB+TJ4AgeRiPYPUIBmL36nCV4AXz8Z5VZmECFcUH/y9FtvSyL/LCpp7H5eMbdVNE+P0 X-OriginatorOrg: prodrive-technologies.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Apr 2026 10:09:36.0224 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b05fa4d7-3d42-4b82-14c5-08dea05741e0 X-MS-Exchange-CrossTenant-Id: 612607c9-5af7-4e7f-8976-faf1ae77be60 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=612607c9-5af7-4e7f-8976-faf1ae77be60;Ip=[212.61.153.67];Helo=[webmail.prodrive.nl] X-MS-Exchange-CrossTenant-AuthSource: AMS0EPF000001B0.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI2PR02MB10999 The main channel Received Signal Strength Indicator (RSSI) measurement is used to determine whether an RF field is present or not. RSSI != 0 is interpreted as an RF Field is present. This does not take RF noise and measurement inaccuracy into account, and results in false positives in the field. Define a noise level and make sure the RF field is only interpreted as present when the RSSI is above the noise level. Fixes: 851ee3cbf850 ("NFC: trf7970a: Don't turn on RF if there is already an RF field") Signed-off-by: Paul Geurts --- drivers/nfc/trf7970a.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c index d17c701c7888..08c27bb438b5 100644 --- a/drivers/nfc/trf7970a.c +++ b/drivers/nfc/trf7970a.c @@ -317,6 +317,7 @@ #define TRF7970A_RSSI_OSC_STATUS_RSSI_MASK (BIT(2) | BIT(1) | BIT(0)) #define TRF7970A_RSSI_OSC_STATUS_RSSI_X_MASK (BIT(5) | BIT(4) | BIT(3)) #define TRF7970A_RSSI_OSC_STATUS_RSSI_OSC_OK BIT(6) +#define TRF7970A_RSSI_OSC_STATUS_RSSI_NOISE_LEVEL 1 #define TRF7970A_SPECIAL_FCN_REG1_COL_7_6 BIT(0) #define TRF7970A_SPECIAL_FCN_REG1_14_ANTICOLL BIT(1) @@ -1300,7 +1301,7 @@ static int trf7970a_is_rf_field(struct trf7970a *trf, bool *is_rf_field) if (ret) return ret; - if (rssi & TRF7970A_RSSI_OSC_STATUS_RSSI_MASK) + if ((rssi & TRF7970A_RSSI_OSC_STATUS_RSSI_MASK) > TRF7970A_RSSI_OSC_STATUS_RSSI_NOISE_LEVEL) *is_rf_field = true; else *is_rf_field = false; -- 2.39.2