From a9bc28aa4e64320668131349436a650bf42591a5 Mon Sep 17 00:00:00 2001 From: Paul Geurts Date: Wed, 22 Apr 2026 12:09:30 +0200 Subject: NFC: trf7970a: Ignore antenna noise when checking for RF field 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 Reviewed-by: Krzysztof Kozlowski Reviewed-by: Mark Greer Link: https://patch.msgid.link/20260422100930.581237-1-paul.geurts@prodrive-technologies.com Signed-off-by: Jakub Kicinski --- 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; -- cgit v1.2.3