diff mbox series

[2/2] NFC: trf7970a: Create device-tree parameter for RX gain reduction

Message ID AM0PR09MB2675AB84E150CCF698CF73BC95082@AM0PR09MB2675.eurprd09.prod.outlook.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series trf7970a: Device tree option for RX gain reduction | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Guessed tree name to be net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 926 this patch: 926
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 1 maintainers not CCed: krzysztof.kozlowski@linaro.org
netdev/build_clang success Errors and warnings before: 937 this patch: 937
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 937 this patch: 937
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns WARNING: line length of 85 exceeds 80 columns WARNING: line length of 87 exceeds 80 columns WARNING: line length of 89 exceeds 80 columns WARNING: line length of 92 exceeds 80 columns WARNING: line length of 94 exceeds 80 columns WARNING: line length of 99 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-04-17--09-00 (tests: 959)

Commit Message

Paul Geurts April 16, 2024, 10:18 p.m. UTC 
The TRF7970a device is sensitive to RF disturbances, which can make it
hard to pass some EMC immunity tests. By reducing the RX antenna gain,
the device becomes less sensitive to EMC disturbances, as a trade-off
against antenna performance.

Add a device tree option to select RX gain reduction to improve EMC
performance.

Selecting a communication standard in the ISO control register resets
the RX antenna gain settings. Therefore set the RX gain reduction
everytime the ISO control register changes, when the option is used.

Signed-off-by: Paul Geurts <paul_geurts@live.nl>
---
 drivers/nfc/trf7970a.c | 86 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 75 insertions(+), 11 deletions(-)
diff mbox series

Patch

diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index 7eb17f46a815..0991c717a5de 100644
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -274,10 +274,14 @@ 
 
 #define TRF7970A_RX_SPECIAL_SETTINGS_NO_LIM	BIT(0)
 #define TRF7970A_RX_SPECIAL_SETTINGS_AGCR	BIT(1)
-#define TRF7970A_RX_SPECIAL_SETTINGS_GD_0DB	(0x0 << 2)
-#define TRF7970A_RX_SPECIAL_SETTINGS_GD_5DB	(0x1 << 2)
-#define TRF7970A_RX_SPECIAL_SETTINGS_GD_10DB	(0x2 << 2)
-#define TRF7970A_RX_SPECIAL_SETTINGS_GD_15DB	(0x3 << 2)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT	2
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX	(0x3)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_MASK	(TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX << \
+							TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_0DB	(0x0 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_5DB	(0x1 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_10DB	(0x2 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
+#define TRF7970A_RX_SPECIAL_SETTINGS_GD_15DB	(0x3 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
 #define TRF7970A_RX_SPECIAL_SETTINGS_HBT	BIT(4)
 #define TRF7970A_RX_SPECIAL_SETTINGS_M848	BIT(5)
 #define TRF7970A_RX_SPECIAL_SETTINGS_C424	BIT(6)
@@ -451,6 +455,8 @@  struct trf7970a {
 	unsigned int			timeout;
 	bool				ignore_timeout;
 	struct delayed_work		timeout_work;
+	u8				rx_gain_reduction;
+	bool			custom_rx_gain_reduction;
 };
 
 static int trf7970a_cmd(struct trf7970a *trf, u8 opcode)
@@ -550,6 +556,41 @@  static int trf7970a_read_irqstatus(struct trf7970a *trf, u8 *status)
 	return ret;
 }
 
+static int trf7970a_update_rx_gain_reduction(struct trf7970a *trf)
+{
+	int ret = 0;
+	u8 reg;
+
+	if (!trf->custom_rx_gain_reduction)
+		return 0;
+
+	ret = trf7970a_read(trf, TRF7970A_RX_SPECIAL_SETTINGS, &reg);
+	if (ret)
+		return ret;
+	reg &= ~(TRF7970A_RX_SPECIAL_SETTINGS_GD_MASK);
+	reg |= trf->rx_gain_reduction;
+
+	ret = trf7970a_write(trf, TRF7970A_RX_SPECIAL_SETTINGS, reg);
+
+	return ret;
+}
+
+static int trf7970a_update_iso_ctrl_register(struct trf7970a *trf, u8 iso_ctrl)
+{
+	int ret;
+
+	ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
+	if (ret)
+		return ret;
+	/*
+	 * Every time the ISO_CTRL register is written, the RX special setting register is reset by
+	 * the chip. When a custom gain reguduction is required, it should be rewritten now.
+	 */
+	ret = trf7970a_update_rx_gain_reduction(trf);
+
+	return ret;
+}
+
 static int trf7970a_read_target_proto(struct trf7970a *trf, u8 *target_proto)
 {
 	int ret;
@@ -929,8 +970,7 @@  static irqreturn_t trf7970a_irq(int irq, void *dev_id)
 			}
 
 			if (iso_ctrl != trf->iso_ctrl) {
-				ret = trf7970a_write(trf, TRF7970A_ISO_CTRL,
-						     iso_ctrl);
+				ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
 				if (ret)
 					goto err_unlock_exit;
 
@@ -1034,6 +1074,11 @@  static int trf7970a_init(struct trf7970a *trf)
 	if (ret)
 		goto err_out;
 
+	/* Set the gain reduction after soft init */
+	ret = trf7970a_update_rx_gain_reduction(trf);
+	if (ret)
+		goto err_out;
+
 	ret = trf7970a_cmd(trf, TRF7970A_CMD_IDLE);
 	if (ret)
 		goto err_out;
@@ -1308,7 +1353,7 @@  static int trf7970a_in_config_framing(struct trf7970a *trf, int framing)
 	}
 
 	if (iso_ctrl != trf->iso_ctrl) {
-		ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
+		ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
 		if (ret)
 			return ret;
 
@@ -1440,7 +1485,7 @@  static int trf7970a_per_cmd_config(struct trf7970a *trf,
 		}
 
 		if (iso_ctrl != trf->iso_ctrl) {
-			ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
+			ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
 			if (ret)
 				return ret;
 
@@ -1604,8 +1649,7 @@  static int trf7970a_tg_config_rf_tech(struct trf7970a *trf, int tech)
 	 */
 	if ((trf->framing == NFC_DIGITAL_FRAMING_NFC_DEP_ACTIVATED) &&
 	    (trf->iso_ctrl_tech != trf->iso_ctrl)) {
-		ret = trf7970a_write(trf, TRF7970A_ISO_CTRL,
-				     trf->iso_ctrl_tech);
+		ret = trf7970a_update_iso_ctrl_register(trf, trf->iso_ctrl_tech);
 
 		trf->iso_ctrl = trf->iso_ctrl_tech;
 	}
@@ -1653,7 +1697,7 @@  static int trf7970a_tg_config_framing(struct trf7970a *trf, int framing)
 	trf->framing = framing;
 
 	if (iso_ctrl != trf->iso_ctrl) {
-		ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
+		ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
 		if (ret)
 			return ret;
 
@@ -1754,6 +1798,10 @@  static int _trf7970a_tg_listen(struct nfc_digital_dev *ddev, u16 timeout,
 	if (ret)
 		goto out_err;
 
+	ret = trf7970a_update_rx_gain_reduction(trf);
+	if (ret)
+		goto out_err;
+
 	ret = trf7970a_write(trf, TRF7970A_REG_IO_CTRL,
 			     trf->io_ctrl | TRF7970A_REG_IO_CTRL_VRS(0x1));
 	if (ret)
@@ -1944,6 +1992,10 @@  static int trf7970a_startup(struct trf7970a *trf)
 	if (ret)
 		return ret;
 
+	ret = trf7970a_update_rx_gain_reduction(trf);
+	if (ret)
+		return ret;
+
 	pm_runtime_set_active(trf->dev);
 	pm_runtime_enable(trf->dev);
 	pm_runtime_mark_last_busy(trf->dev);
@@ -1992,6 +2044,7 @@  static int trf7970a_probe(struct spi_device *spi)
 	struct trf7970a *trf;
 	int uvolts, autosuspend_delay, ret;
 	u32 clk_freq = TRF7970A_13MHZ_CLOCK_FREQUENCY;
+	u32 rx_gain_reduction;
 
 	if (!np) {
 		dev_err(&spi->dev, "No Device Tree entry\n");
@@ -2053,6 +2106,17 @@  static int trf7970a_probe(struct spi_device *spi)
 		trf->modulator_sys_clk_ctrl = 0;
 	}
 
+	if (of_property_read_u32(np, "rx-gain-reduction", &rx_gain_reduction) == 0) {
+		if (rx_gain_reduction > TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX) {
+			dev_warn(trf->dev, "invalid RX gain reduction setting: %u. Limiting to %u\n",
+				 rx_gain_reduction, TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX);
+			rx_gain_reduction = TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX;
+		}
+		trf->rx_gain_reduction = (rx_gain_reduction <<
+			TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT);
+		trf->custom_rx_gain_reduction = true;
+	}
+
 	ret = devm_request_threaded_irq(trf->dev, spi->irq, NULL,
 					trf7970a_irq,
 					IRQF_TRIGGER_RISING | IRQF_ONESHOT,