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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
NFC: trf7970a: Create device-tree parameter for RX gain reduction
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@prodrive-technologies.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250626141242.3749958-3-paul.geurts@prodrive-technologies.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
authored by
Paul Geurts
and committed by
Jakub Kicinski
5d693518
2bee162a
+80
-11
+80
-11
drivers/nfc/trf7970a.c
+80
-11
drivers/nfc/trf7970a.c
···
272
272
#define TRF7970A_MODULATOR_EN_OOK BIT(6)
273
273
#define TRF7970A_MODULATOR_27MHZ BIT(7)
274
274
275
+
#define TRF7970A_RX_GAIN_REDUCTION_MAX_DB 15
276
+
#define TRF7970A_RX_GAIN_REDUCTION_DB_PER_LSB 5
275
277
#define TRF7970A_RX_SPECIAL_SETTINGS_NO_LIM BIT(0)
276
278
#define TRF7970A_RX_SPECIAL_SETTINGS_AGCR BIT(1)
277
-
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_0DB (0x0 << 2)
278
-
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_5DB (0x1 << 2)
279
-
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_10DB (0x2 << 2)
280
-
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_15DB (0x3 << 2)
279
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT 2
280
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX (0x3)
281
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_MASK (TRF7970A_RX_SPECIAL_SETTINGS_GD_MAX << \
282
+
TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
283
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_0DB (0x0 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
284
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_5DB (0x1 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
285
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_10DB (0x2 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
286
+
#define TRF7970A_RX_SPECIAL_SETTINGS_GD_15DB (0x3 << TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT)
281
287
#define TRF7970A_RX_SPECIAL_SETTINGS_HBT BIT(4)
282
288
#define TRF7970A_RX_SPECIAL_SETTINGS_M848 BIT(5)
283
289
#define TRF7970A_RX_SPECIAL_SETTINGS_C424 BIT(6)
···
458
452
unsigned int timeout;
459
453
bool ignore_timeout;
460
454
struct delayed_work timeout_work;
455
+
u8 rx_gain_reduction;
456
+
bool custom_rx_gain_reduction;
461
457
};
462
458
463
459
static int trf7970a_cmd(struct trf7970a *trf, u8 opcode)
···
555
547
__func__, ret);
556
548
else
557
549
*status = buf[0];
550
+
551
+
return ret;
552
+
}
553
+
554
+
static int trf7970a_update_rx_gain_reduction(struct trf7970a *trf)
555
+
{
556
+
int ret = 0;
557
+
u8 reg;
558
+
559
+
if (!trf->custom_rx_gain_reduction)
560
+
return 0;
561
+
562
+
ret = trf7970a_read(trf, TRF7970A_RX_SPECIAL_SETTINGS, ®);
563
+
if (ret)
564
+
return ret;
565
+
reg &= ~(TRF7970A_RX_SPECIAL_SETTINGS_GD_MASK);
566
+
reg |= trf->rx_gain_reduction;
567
+
568
+
ret = trf7970a_write(trf, TRF7970A_RX_SPECIAL_SETTINGS, reg);
569
+
570
+
return ret;
571
+
}
572
+
573
+
static int trf7970a_update_iso_ctrl_register(struct trf7970a *trf, u8 iso_ctrl)
574
+
{
575
+
int ret;
576
+
577
+
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
578
+
if (ret)
579
+
return ret;
580
+
/*
581
+
* Every time the ISO_CTRL register is written, the RX special setting register is reset by
582
+
* the chip. When a custom gain reguduction is required, it should be rewritten now.
583
+
*/
584
+
ret = trf7970a_update_rx_gain_reduction(trf);
558
585
559
586
return ret;
560
587
}
···
973
930
}
974
931
975
932
if (iso_ctrl != trf->iso_ctrl) {
976
-
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL,
977
-
iso_ctrl);
933
+
ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
978
934
if (ret)
979
935
goto err_unlock_exit;
980
936
···
1074
1032
dev_dbg(trf->dev, "Initializing device - state: %d\n", trf->state);
1075
1033
1076
1034
ret = trf7970a_cmd(trf, TRF7970A_CMD_SOFT_INIT);
1035
+
if (ret)
1036
+
goto err_out;
1037
+
1038
+
/* Set the gain reduction after soft init */
1039
+
ret = trf7970a_update_rx_gain_reduction(trf);
1077
1040
if (ret)
1078
1041
goto err_out;
1079
1042
···
1356
1309
}
1357
1310
1358
1311
if (iso_ctrl != trf->iso_ctrl) {
1359
-
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
1312
+
ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
1360
1313
if (ret)
1361
1314
return ret;
1362
1315
···
1488
1441
}
1489
1442
1490
1443
if (iso_ctrl != trf->iso_ctrl) {
1491
-
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
1444
+
ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
1492
1445
if (ret)
1493
1446
return ret;
1494
1447
···
1652
1605
*/
1653
1606
if ((trf->framing == NFC_DIGITAL_FRAMING_NFC_DEP_ACTIVATED) &&
1654
1607
(trf->iso_ctrl_tech != trf->iso_ctrl)) {
1655
-
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL,
1656
-
trf->iso_ctrl_tech);
1608
+
ret = trf7970a_update_iso_ctrl_register(trf, trf->iso_ctrl_tech);
1657
1609
1658
1610
trf->iso_ctrl = trf->iso_ctrl_tech;
1659
1611
}
···
1700
1654
trf->framing = framing;
1701
1655
1702
1656
if (iso_ctrl != trf->iso_ctrl) {
1703
-
ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
1657
+
ret = trf7970a_update_iso_ctrl_register(trf, iso_ctrl);
1704
1658
if (ret)
1705
1659
return ret;
1706
1660
···
1798
1752
TRF7970A_RX_SPECIAL_SETTINGS_M848 |
1799
1753
TRF7970A_RX_SPECIAL_SETTINGS_C424 |
1800
1754
TRF7970A_RX_SPECIAL_SETTINGS_C212);
1755
+
if (ret)
1756
+
goto out_err;
1757
+
1758
+
ret = trf7970a_update_rx_gain_reduction(trf);
1801
1759
if (ret)
1802
1760
goto out_err;
1803
1761
···
1995
1945
if (ret)
1996
1946
return ret;
1997
1947
1948
+
ret = trf7970a_update_rx_gain_reduction(trf);
1949
+
if (ret)
1950
+
return ret;
1951
+
1998
1952
pm_runtime_set_active(trf->dev);
1999
1953
pm_runtime_enable(trf->dev);
2000
1954
pm_runtime_mark_last_busy(trf->dev);
···
2047
1993
struct trf7970a *trf;
2048
1994
int uvolts, autosuspend_delay, ret;
2049
1995
u32 clk_freq = TRF7970A_13MHZ_CLOCK_FREQUENCY;
1996
+
u32 rx_gain_reduction_db;
2050
1997
2051
1998
if (!np) {
2052
1999
dev_err(&spi->dev, "No Device Tree entry\n");
···
2107
2052
dev_dbg(trf->dev, "trf7970a configured for 27MHz crystal\n");
2108
2053
} else {
2109
2054
trf->modulator_sys_clk_ctrl = 0;
2055
+
}
2056
+
2057
+
if (of_property_read_u32(np, "ti,rx-gain-reduction-db", &rx_gain_reduction_db) == 0) {
2058
+
if (rx_gain_reduction_db > TRF7970A_RX_GAIN_REDUCTION_MAX_DB) {
2059
+
dev_warn(trf->dev, "RX Gain reduction too high. Ignored\n");
2060
+
} else if ((rx_gain_reduction_db % TRF7970A_RX_GAIN_REDUCTION_DB_PER_LSB)) {
2061
+
dev_warn(trf->dev, "RX Gain must be set in 5 dB increments. Ignored\n");
2062
+
} else {
2063
+
dev_dbg(trf->dev, "RX gain set to -%udB\n", rx_gain_reduction_db);
2064
+
trf->rx_gain_reduction = ((rx_gain_reduction_db /
2065
+
TRF7970A_RX_GAIN_REDUCTION_DB_PER_LSB) <<
2066
+
TRF7970A_RX_SPECIAL_SETTINGS_GD_SHIFT);
2067
+
trf->custom_rx_gain_reduction = true;
2068
+
}
2110
2069
}
2111
2070
2112
2071
ret = devm_request_threaded_irq(trf->dev, spi->irq, NULL,