[PATCH] media: dvb-frontends: a8293: fix LNB powerup failure in PCTV 461e

From: Chuck Ritola
Date: Thu Nov 18 2021 - 21:09:54 EST

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Fixes a8293 failure to raise LNB voltage in PCTV 461e DVB-S2 Stick
affecting multiple users over several years as found here:

http://www.linuxquestions.org/questions/linux-hardware-18/pctv-dvb-s2-stick-461e-not-feeding-lnb-4175529374/
https://www.linuxtv.org/wiki/index.php/Pinnacle_PCTV_DVB-S2_Stick_(461e)
https://github.com/OpenELEC/OpenELEC.tv/issues/3731

Caused by vIN undervoltage lockout (status register bit 7) when raising LNB to 18V.
Addressed by using the higher-precision voltages available on the a8293 to gradually
increase (slew) the voltage when voltage increases are requested.

Adds volt_slew_nanos_per_mv to a8293_platform_data struct for specifying slew rate.
If value is <1 or non-sane (>1600), the original no-slew version for a8293_set_voltage is used.

Signed-off-by: Chuck Ritola <cjritola@xxxxxxxxx>
---
drivers/media/dvb-frontends/a8293.c | 147 +++++++++++++++++++++++++-
drivers/media/dvb-frontends/a8293.h | 2 +
drivers/media/usb/em28xx/em28xx-dvb.c | 3 +
3 files changed, 150 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-frontends/a8293.c b/drivers/media/dvb-frontends/a8293.c
index 57f52c004..f86af43ee 100644
--- a/drivers/media/dvb-frontends/a8293.c
+++ b/drivers/media/dvb-frontends/a8293.c
@@ -3,16 +3,139 @@
* Allegro A8293 SEC driver
*
* Copyright (C) 2011 Antti Palosaari <crope@xxxxxx>
+ * Copyright (C) 2021 Chuck Ritola <cjritola@xxxxxxxxx>
*/

#include "a8293.h"

+#define A8293_FLAG_ODT 0x10
+
+
struct a8293_dev {
struct i2c_client *client;
u8 reg[2];
+ int volt_slew_nanos_per_mv;
};

-static int a8293_set_voltage(struct dvb_frontend *fe,
+/*
+ * When increasing voltage, do so in minimal steps over time, minimizing risk of vIN undervoltage.
+ */
+
+static int a8293_set_voltage_slew(struct a8293_dev *dev,
+ struct i2c_client *client,
+ enum fe_sec_voltage fe_sec_voltage,
+ int min_nanos_per_mv)
+{
+ int ret;
+ u8 reg0, reg1;
+ int new_volt_idx;
+ const int idx_to_mv[] = {0, 12709, 13042, 13375, 14042, 15042, 18042, 18709, 19042};
+ const u8 idx_to_reg[] = {0x00, 0x20, 0x21, 0x22, 0x24, 0x27, 0x28, 0x2A, 0x2B };
+ int this_volt_idx;
+ u8 status;
+ int prev_volt_idx;
+
+ dev_dbg(&client->dev, "set_voltage_slew fe_sec_voltage=%d\n", fe_sec_voltage);
+
+ /* Read status register to clear any stale faults. */
+ ret = i2c_master_recv(client, &status, 1);
+ if (ret < 0)
+ goto err;
+
+ /* Determine previous voltage */
+ switch (dev->reg[0] & 0x2F) {
+ case 0x00:
+ prev_volt_idx = 0;
+ break;
+ case 0x20:
+ prev_volt_idx = 1;
+ break;
+ case 0x21:
+ prev_volt_idx = 2;
+ break;
+ case 0x22:
+ prev_volt_idx = 3;
+ break;
+ case 0x24:
+ prev_volt_idx = 4;
+ break;
+ case 0x27:
+ prev_volt_idx = 5;
+ break;
+ case 0x28:
+ prev_volt_idx = 6;
+ break;
+ case 0x2A:
+ prev_volt_idx = 7;
+ break;
+ case 0x2B:
+ prev_volt_idx = 8;
+ break;
+ default:
+ prev_volt_idx = 0;
+ }
+
+ /* Determine new voltage */
+ switch (fe_sec_voltage) {
+ case SEC_VOLTAGE_OFF:
+ new_volt_idx = 0;
+ break;
+ case SEC_VOLTAGE_13:
+ new_volt_idx = 2;
+ break;
+ case SEC_VOLTAGE_18:
+ new_volt_idx = 6;
+ break;
+ default:
+ ret = -EINVAL;
+ goto err;
+ }
+
+ /* Slew to new voltage if new voltage is greater than current voltage */
+ this_volt_idx = prev_volt_idx;
+ if (this_volt_idx < new_volt_idx) {
+ while (this_volt_idx < new_volt_idx) {
+ int delta_mv = idx_to_mv[this_volt_idx+1] - idx_to_mv[this_volt_idx];
+ int min_wait_time = delta_mv * min_nanos_per_mv;
+
+ reg0 = idx_to_reg[this_volt_idx+1];
+ reg0 |= A8293_FLAG_ODT;
+
+ ret = i2c_master_send(client, &reg0, 1);
+ if (ret < 0)
+ goto err;
+ dev->reg[0] = reg0;
+ this_volt_idx++;
+ usleep_range(min_wait_time, min_wait_time * 2);
+ }
+ } else { /* Else just set the voltage */
+ reg0 = idx_to_reg[new_volt_idx];
+ reg0 |= A8293_FLAG_ODT;
+ ret = i2c_master_send(client, &reg0, 1);
+ if (ret < 0)
+ goto err;
+ dev->reg[0] = reg0;
+ }
+
+ /* TMODE=0, TGATE=1 */
+ reg1 = 0x82;
+ if (reg1 != dev->reg[1]) {
+ ret = i2c_master_send(client, &reg1, 1);
+ if (ret < 0)
+ goto err;
+ dev->reg[1] = reg1;
+ }
+
+ usleep_range(1500, 5000);
+
+ return 0;
+err:
+ dev_dbg(&client->dev, "failed=%d\n", ret);
+ return ret;
+}
+
+
+static int a8293_set_voltage_noslew(struct dvb_frontend *fe,
enum fe_sec_voltage fe_sec_voltage)
{
struct a8293_dev *dev = fe->sec_priv;
@@ -20,7 +143,7 @@ static int a8293_set_voltage(struct dvb_frontend *fe,
int ret;
u8 reg0, reg1;

- dev_dbg(&client->dev, "fe_sec_voltage=%d\n", fe_sec_voltage);
+ dev_dbg(&client->dev, "set_voltage_noslew fe_sec_voltage=%d\n", fe_sec_voltage);

switch (fe_sec_voltage) {
case SEC_VOLTAGE_OFF:
@@ -62,6 +185,24 @@ static int a8293_set_voltage(struct dvb_frontend *fe,
return ret;
}

+static int a8293_set_voltage(struct dvb_frontend *fe,
+ enum fe_sec_voltage fe_sec_voltage)
+{
+ struct a8293_dev *dev = fe->sec_priv;
+ struct i2c_client *client = dev->client;
+ int volt_slew_nanos_per_mv = dev->volt_slew_nanos_per_mv;
+
+ dev_dbg(&client->dev, "set_voltage volt_slew_nanos_per_mv=%d\n", volt_slew_nanos_per_mv);
+
+ /* Use slew version if slew rate is set to a sane value */
+ if (volt_slew_nanos_per_mv > 0 && volt_slew_nanos_per_mv < 1600)
+ a8293_set_voltage_slew(dev, client, fe_sec_voltage, volt_slew_nanos_per_mv);
+ else
+ a8293_set_voltage_noslew(fe, fe_sec_voltage);
+
+ return 0;
+}
+
static int a8293_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
@@ -78,6 +219,7 @@ static int a8293_probe(struct i2c_client *client,
}

dev->client = client;
+ dev->volt_slew_nanos_per_mv = pdata->volt_slew_nanos_per_mv;

/* check if the SEC is there */
ret = i2c_master_recv(client, buf, 2);
@@ -127,5 +269,6 @@ static struct i2c_driver a8293_driver = {
module_i2c_driver(a8293_driver);

MODULE_AUTHOR("Antti Palosaari <crope@xxxxxx>");
+MODULE_AUTHOR("Chuck Ritola <cjritola@xxxxxxxxx>");
MODULE_DESCRIPTION("Allegro A8293 SEC driver");
MODULE_LICENSE("GPL");
diff --git a/drivers/media/dvb-frontends/a8293.h b/drivers/media/dvb-frontends/a8293.h
index 8c09635ef..0a807c022 100644
--- a/drivers/media/dvb-frontends/a8293.h
+++ b/drivers/media/dvb-frontends/a8293.h
@@ -18,9 +18,11 @@
/**
* struct a8293_platform_data - Platform data for the a8293 driver
* @dvb_frontend: DVB frontend.
+ * @volt_slew_nanos_per_mv: Slew rate when increasing LNB voltage, in nanoseconds per millivolt.
*/
struct a8293_platform_data {
struct dvb_frontend *dvb_frontend;
+ int volt_slew_nanos_per_mv;
};

#endif /* A8293_H */
diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
index 471bd7466..859f4a33e 100644
--- a/drivers/media/usb/em28xx/em28xx-dvb.c
+++ b/drivers/media/usb/em28xx/em28xx-dvb.c
@@ -1208,6 +1208,9 @@ static int em28178_dvb_init_pctv_461e(struct em28xx *dev)

/* attach SEC */
a8293_pdata.dvb_frontend = dvb->fe[0];
+ /* 461e has a tendency to have vIN undervoltage troubles. Slew mitigates this. */
+ a8293_pdata.volt_slew_nanos_per_mv = 20;
+
dvb->i2c_client_sec = dvb_module_probe("a8293", NULL,
&dev->i2c_adap[dev->def_i2c_bus],
0x08, &a8293_pdata);
--
2.20.1

Next message: tongtiangen: "Re: [PATCH 03/12] riscv: switch to relative exception tables"
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