[RFC, WIP, v5 03/10] media: vidtv: implement a demodulator driver

Daniel W. S. Almeida
2020-05-15T21:48:55Z

Implement a I2C demodulator driver, simulating support for DVB-T, DVB-C
and DVB-S.

This demodulator will periodically check the signal quality against a table
and drop the TS lock if it drops below a threshold value, regaining it in
the event that the signal improves.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
drivers/media/test-drivers/vidtv/Makefile | 2 +-
.../media/test-drivers/vidtv/vidtv_demod.c | 448 ++++++++++++++++++
.../media/test-drivers/vidtv/vidtv_demod.h | 42 ++
3 files changed, 491 insertions(+), 1 deletion(-)
create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.c
create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.h

diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index e625810a82603..36ba00ddc0d1e 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -1,3 +1,3 @@
# SPDX-License-Identifier: GPL-2.0

-obj-$(CONFIG_DVB_VIDTV) += vidtv_tuner.o
+obj-$(CONFIG_DVB_VIDTV) += vidtv_tuner.o vidtv_demod.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.c b/drivers/media/test-drivers/vidtv/vidtv_demod.c
new file mode 100644
index 0000000000000..2d5270e71a909
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_demod.c
@@ -0,0 +1,448 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ * Based on the example driver written by Emard <emard@softhome.net>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/random.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <media/dvb_frontend.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_demod.h"
+
+MODULE_DESCRIPTION("Virtual DVB Demodulator Driver");
+MODULE_AUTHOR("Daniel W. S. Almeida");
+MODULE_LICENSE("GPL");
+
+#define POLL_THRD_TIME 2000 /* msecs */
+
+static struct vidtv_demod_cnr_to_qual_s vidtv_demod_c_cnr_2_qual[] = {
+ /* from libdvbv5 source code, in milli db */
+ { QAM_256, FEC_NONE, 34000, 38000},
+ { QAM_64, FEC_NONE, 30000, 34000},
+};
+
+static struct vidtv_demod_cnr_to_qual_s vidtv_demod_s_cnr_2_qual[] = {
+ /* from libdvbv5 source code, in milli db */
+ { QPSK, FEC_1_2, 7000, 10000},
+ { QPSK, FEC_2_3, 9000, 12000},
+ { QPSK, FEC_3_4, 10000, 13000},
+ { QPSK, FEC_5_6, 11000, 14000},
+ { QPSK, FEC_7_8, 12000, 15000},
+};
+
+static struct vidtv_demod_cnr_to_qual_s vidtv_demod_s2_cnr_2_qual[] = {
+ /* from libdvbv5 source code, in milli db */
+ { QPSK, FEC_1_2, 9000, 12000},
+ { QPSK, FEC_2_3, 11000, 14000},
+ { QPSK, FEC_3_4, 12000, 15000},
+ { QPSK, FEC_5_6, 12000, 15000},
+ { QPSK, FEC_8_9, 13000, 16000},
+ { QPSK, FEC_9_10, 13500, 16500},
+ { PSK_8, FEC_2_3, 14500, 17500},
+ { PSK_8, FEC_3_4, 16000, 19000},
+ { PSK_8, FEC_5_6, 17500, 20500},
+ { PSK_8, FEC_8_9, 19000, 22000},
+};
+
+static struct vidtv_demod_cnr_to_qual_s vidtv_demod_t_cnr_2_qual[] = {
+ /* from libdvbv5 source code, in milli db*/
+ { QPSK, FEC_1_2, 4100, 5900},
+ { QPSK, FEC_2_3, 6100, 9600},
+ { QPSK, FEC_3_4, 7200, 12400},
+ { QPSK, FEC_5_6, 8500, 15600},
+ { QPSK, FEC_7_8, 9200, 17500},
+
+ { QAM_16, FEC_1_2, 9800, 11800},
+ { QAM_16, FEC_2_3, 12100, 15300},
+ { QAM_16, FEC_3_4, 13400, 18100},
+ { QAM_16, FEC_5_6, 14800, 21300},
+ { QAM_16, FEC_7_8, 15700, 23600},
+
+ { QAM_64, FEC_1_2, 14000, 16000},
+ { QAM_64, FEC_2_3, 19900, 25400},
+ { QAM_64, FEC_3_4, 24900, 27900},
+ { QAM_64, FEC_5_6, 21300, 23300},
+ { QAM_64, FEC_7_8, 22000, 24000},
+};
+
+static struct vidtv_demod_cnr_to_qual_s
+*vidtv_match_cnr_s(struct dvb_frontend *fe)
+{
+ struct dtv_frontend_properties *c;
+ struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+ u32 array_size = 0;
+ u32 i;
+
+ c = &fe->dtv_property_cache;
+
+ switch (c->delivery_system) {
+ case SYS_DVBT:
+ case SYS_DVBT2:
+ cnr2qual = vidtv_demod_t_cnr_2_qual;
+ array_size = ARRAY_SIZE(vidtv_demod_t_cnr_2_qual);
+ break;
+
+ case SYS_DVBS:
+ cnr2qual = vidtv_demod_s_cnr_2_qual;
+ array_size = ARRAY_SIZE(vidtv_demod_s_cnr_2_qual);
+ break;
+
+ case SYS_DVBS2:
+ cnr2qual = vidtv_demod_s2_cnr_2_qual;
+ array_size = ARRAY_SIZE(vidtv_demod_s2_cnr_2_qual);
+ break;
+
+ case SYS_DVBC_ANNEX_A:
+ cnr2qual = vidtv_demod_c_cnr_2_qual;
+ array_size = ARRAY_SIZE(vidtv_demod_c_cnr_2_qual);
+ break;
+
+ default:
+ pr_warn_ratelimited("%s: unsupported delivery system: %u\n",
+ __func__,
+ c->delivery_system);
+ break;
+ }
+
+ for (i = 0; i <= array_size; i++)
+ if (cnr2qual[i].modulation == c->modulation &&
+ cnr2qual[i].fec == c->fec_inner)
+ return &cnr2qual[i];
+
+ return NULL; /* not found */
+}
+
+static void vidtv_demod_poll_snr_handler(struct work_struct *work)
+{
+ /*
+ * periodically check the signal quality and eventually
+ * lose the TS lock if it dips too low
+ */
+ struct vidtv_demod_state *state;
+ struct dtv_frontend_properties *c;
+ struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+ struct vidtv_demod_config *config;
+ u16 snr = 0;
+
+ state = container_of(work, struct vidtv_demod_state, poll_snr.work);
+ c = &state->frontend.dtv_property_cache;
+ config = &state->config;
+
+ if (!state->frontend.ops.tuner_ops.get_rf_strength)
+ return;
+
+ state->frontend.ops.tuner_ops.get_rf_strength(&state->frontend, &snr);
+
+ cnr2qual = vidtv_match_cnr_s(&state->frontend);
+ if (!cnr2qual)
+ return;
+
+ if (snr < cnr2qual->cnr_ok) {
+ /* eventually lose the TS lock */
+ if (prandom_u32_max(100) < config->drop_tslock_prob_on_low_snr)
+ state->status = 0;
+ } else {
+ /* recover if the signal improves */
+ if (prandom_u32_max(100) <
+ config->recover_tslock_prob_on_good_snr)
+ state->status = FE_HAS_SIGNAL |
+ FE_HAS_CARRIER |
+ FE_HAS_VITERBI |
+ FE_HAS_SYNC |
+ FE_HAS_LOCK;
+ }
+
+ schedule_delayed_work(&state->poll_snr,
+ msecs_to_jiffies(POLL_THRD_TIME));
+}
+
+static int vidtv_demod_read_status(struct dvb_frontend *fe,
+ enum fe_status *status)
+{
+ struct vidtv_demod_state *state = fe->demodulator_priv;
+
+ *status = state->status;
+
+ return 0;
+}
+
+static int vidtv_demod_read_ber(struct dvb_frontend *fe, u32 *ber)
+{
+ *ber = 0;
+ return 0;
+}
+
+static int vidtv_demod_read_signal_strength(struct dvb_frontend *fe,
+ u16 *strength)
+{
+ *strength = 0;
+ return 0;
+}
+
+static int vidtv_demod_read_snr(struct dvb_frontend *fe, u16 *snr)
+{
+ *snr = 0;
+ return 0;
+}
+
+static int vidtv_demod_read_ucblocks(struct dvb_frontend *fe, u32 *ucblocks)
+{
+ *ucblocks = 0;
+ return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if it actually reads something from the hardware.
+ * Also, it should check for the locks, in order to avoid report wrong data
+ * to userspace.
+ */
+static int vidtv_demod_get_frontend(struct dvb_frontend *fe,
+ struct dtv_frontend_properties *p)
+{
+ return 0;
+}
+
+static int vidtv_demod_set_frontend(struct dvb_frontend *fe)
+{
+ struct vidtv_demod_state *state = fe->demodulator_priv;
+ struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+ u32 tuner_status = 0;
+
+ if (fe->ops.tuner_ops.set_params) {
+ fe->ops.tuner_ops.set_params(fe);
+
+ /* store the CNR returned by the tuner */
+ fe->ops.tuner_ops.get_rf_strength(fe, &state->tuner_cnr);
+
+ fe->ops.tuner_ops.get_status(fe, &tuner_status);
+ state->status = (state->tuner_cnr > 0) ? FE_HAS_SIGNAL |
+ FE_HAS_CARRIER |
+ FE_HAS_VITERBI |
+ FE_HAS_SYNC |
+ FE_HAS_LOCK :
+ 0;
+ cnr2qual = vidtv_match_cnr_s(fe);
+
+ /* signal isn't good: might lose the lock eventually */
+ if (tuner_status == TUNER_STATUS_LOCKED &&
+ state->tuner_cnr < cnr2qual->cnr_good) {
+ schedule_delayed_work(&state->poll_snr,
+ msecs_to_jiffies(POLL_THRD_TIME));
+
+ state->poll_snr_thread_running = true;
+ }
+
+ if (fe->ops.i2c_gate_ctrl)
+ fe->ops.i2c_gate_ctrl(fe, 0);
+ }
+
+ return 0;
+}
+
+static int vidtv_demod_sleep(struct dvb_frontend *fe)
+{
+ struct vidtv_demod_state *state = fe->demodulator_priv;
+
+ if (state->poll_snr_thread_running) {
+ cancel_delayed_work_sync(&state->poll_snr);
+ state->poll_snr_thread_running = false;
+ state->poll_snr_thread_restart = true;
+ }
+ return 0;
+}
+
+static int vidtv_demod_init(struct dvb_frontend *fe)
+{
+ struct vidtv_demod_state *state = fe->demodulator_priv;
+ u32 tuner_status = 0;
+
+ if (state->cold_start)
+ INIT_DELAYED_WORK(&state->poll_snr,
+ &vidtv_demod_poll_snr_handler);
+
+ /*
+ * At resume, start the snr poll thread only if it was suspended with
+ * the thread running. Extra care should be taken here, as some tuner
+ * status change might happen at resume time (for example, due to an
+ * ioctl syscall to set_frontend, or due to a release syscall).
+ */
+ fe->ops.tuner_ops.get_status(fe, &tuner_status);
+
+ if (tuner_status == TUNER_STATUS_LOCKED &&
+ state->poll_snr_thread_restart) {
+ schedule_delayed_work(&state->poll_snr,
+ msecs_to_jiffies(POLL_THRD_TIME));
+
+ state->poll_snr_thread_restart = false;
+ }
+
+ state->cold_start = false;
+ return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if the demod has support for DVB-S or DVB-S2
+ */
+static int vidtv_demod_set_tone(struct dvb_frontend *fe,
+ enum fe_sec_tone_mode tone)
+{
+ return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if the demod has support for DVB-S or DVB-S2
+ */
+static int vidtv_demod_set_voltage(struct dvb_frontend *fe,
+ enum fe_sec_voltage voltage)
+{
+ return 0;
+}
+
+static void vidtv_demod_release(struct dvb_frontend *fe)
+{
+ struct vidtv_demod_state *state = fe->demodulator_priv;
+
+ if (state->poll_snr_thread_running)
+ cancel_delayed_work_sync(&state->poll_snr);
+
+ kfree(state);
+}
+
+static const struct dvb_frontend_ops vidtv_demod_ops = {
+ .delsys = {
+ SYS_DVBT,
+ SYS_DVBT2,
+ SYS_DVBC_ANNEX_A,
+ SYS_DVBS,
+ SYS_DVBS2,
+ },
+
+ .info = {
+ .name = "Dummy demod for DVB-T/T2/C/S/S2",
+ .frequency_min_hz = 51 * MHz,
+ .frequency_max_hz = 2150 * MHz,
+ .frequency_stepsize_hz = 62500,
+ .frequency_tolerance_hz = 29500 * kHz,
+ .symbol_rate_min = 1000000,
+ .symbol_rate_max = 45000000,
+
+ .caps = FE_CAN_FEC_1_2 |
+ FE_CAN_FEC_2_3 |
+ FE_CAN_FEC_3_4 |
+ FE_CAN_FEC_4_5 |
+ FE_CAN_FEC_5_6 |
+ FE_CAN_FEC_6_7 |
+ FE_CAN_FEC_7_8 |
+ FE_CAN_FEC_8_9 |
+ FE_CAN_FEC_AUTO |
+ FE_CAN_QAM_16 |
+ FE_CAN_QAM_64 |
+ FE_CAN_QAM_32 |
+ FE_CAN_QAM_128 |
+ FE_CAN_QAM_256 |
+ FE_CAN_QAM_AUTO |
+ FE_CAN_QPSK |
+ FE_CAN_FEC_AUTO |
+ FE_CAN_INVERSION_AUTO |
+ FE_CAN_TRANSMISSION_MODE_AUTO |
+ FE_CAN_GUARD_INTERVAL_AUTO |
+ FE_CAN_HIERARCHY_AUTO,
+ },
+
+ .release = vidtv_demod_release,
+
+ .init = vidtv_demod_init,
+ .sleep = vidtv_demod_sleep,
+
+ .set_frontend = vidtv_demod_set_frontend,
+ .get_frontend = vidtv_demod_get_frontend,
+
+ .read_status = vidtv_demod_read_status,
+ .read_ber = vidtv_demod_read_ber,
+ .read_signal_strength = vidtv_demod_read_signal_strength,
+ .read_snr = vidtv_demod_read_snr,
+ .read_ucblocks = vidtv_demod_read_ucblocks,
+
+ /* For DVB-S/S2 */
+ .set_voltage = vidtv_demod_set_voltage,
+ .set_tone = vidtv_demod_set_tone,
+};
+
+static const struct i2c_device_id vidtv_demod_i2c_id_table[] = {
+ {"vidtv_demod", 0},
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, vidtv_demod_i2c_id_table);
+
+static int vidtv_demod_i2c_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct vidtv_demod_config *config = client->dev.platform_data;
+ struct vidtv_demod_state *state;
+
+ /* allocate memory for the internal state */
+ state = kzalloc(sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ /* create dvb_frontend */
+ memcpy(&state->frontend.ops,
+ &vidtv_demod_ops,
+ sizeof(struct dvb_frontend_ops));
+
+ state->frontend.demodulator_priv = state;
+ /* return the pointer to the bridge driver */
+ *config->frontend = &state->frontend;
+ i2c_set_clientdata(client, state);
+
+ return 0;
+}
+
+static int vidtv_demod_i2c_remove(struct i2c_client *client)
+{
+ struct vidtv_demod_state *state = i2c_get_clientdata(client);
+
+ memset(&state->frontend.ops, 0, sizeof(struct dvb_frontend_ops));
+ state->frontend.demodulator_priv = NULL;
+ kfree(state);
+
+ return 0;
+}
+
+static struct i2c_driver vidtv_demod_i2c_driver = {
+ .driver = {
+ .name = "vidtv_demod",
+ .suppress_bind_attrs = true,
+ },
+ .probe = vidtv_demod_i2c_probe,
+ .remove = vidtv_demod_i2c_remove,
+ .id_table = vidtv_demod_i2c_id_table,
+};
+
+module_i2c_driver(vidtv_demod_i2c_driver);
diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.h b/drivers/media/test-drivers/vidtv/vidtv_demod.h
new file mode 100644
index 0000000000000..57d810f7a4462
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_demod.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * The Virtual DTV test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ * Based on the example driver written by Emard <emard@softhome.net>
+ */
+
+#ifndef VIDTV_DEMOD_H
+#define VIDTV_DEMOD_H
+
+#include <linux/dvb/frontend.h>
+#include <media/dvb_frontend.h>
+
+struct vidtv_demod_cnr_to_qual_s {
+ /* attempt to use the same values as libdvbv5 */
+ u32 modulation;
+ u32 fec;
+ u32 cnr_ok, cnr_good;
+};
+
+struct vidtv_demod_config {
+ struct dvb_frontend **frontend;
+ /* probability of losing the lock due to low snr */
+ u8 drop_tslock_prob_on_low_snr;
+ /* probability of recovering when the signal improves */
+ u8 recover_tslock_prob_on_good_snr;
+};
+
+struct vidtv_demod_state {
+ struct dvb_frontend frontend;
+ struct vidtv_demod_config config;
+ struct delayed_work poll_snr;
+ enum fe_status status;
+ u16 tuner_cnr;
+ bool cold_start;
+ bool poll_snr_thread_running;
+ bool poll_snr_thread_restart;
+};
+#endif // VIDTV_DEMOD_H
--
2.26.2