Commit a9bc28aa authored by Paul Geurts's avatar Paul Geurts Committed by Jakub Kicinski
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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: 851ee3cb ("NFC: trf7970a: Don't turn on RF if there is already an RF field")
Signed-off-by: default avatarPaul Geurts <paul.geurts@prodrive-technologies.com>
Reviewed-by: default avatarKrzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: default avatarMark Greer <mgreer@animalcreek.com>
Link: https://patch.msgid.link/20260422100930.581237-1-paul.geurts@prodrive-technologies.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent adbe2cdf

drivers/nfc/trf7970a.c

+2 −1
Original line number Diff line number Diff line
@@ -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;