diff mbox series

media: cxd2841er: avoid too many status inquires

Message ID deda32250ad32078b98eb41eb09d6d20050a6f9c.1570113429.git.mchehab+samsung@kernel.org (mailing list archive)
State New, archived
Headers show
Series media: cxd2841er: avoid too many status inquires | expand

Commit Message

Mauro Carvalho Chehab Oct. 3, 2019, 2:37 p.m. UTC
As reported at:
	https://tvheadend.org/issues/5625

Retrieving certain status can cause discontinuity issues.

Prevent that by adding a timeout to each status logic.

Currently, the timeout is estimated based at the channel
bandwidth. There are other parameters that may also affect
the timeout, but that would require a per-delivery system
calculus and probably more information about how cxd2481er
works, with we don't have.

So, do a poor man's best guess.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
---
 drivers/media/dvb-frontends/cxd2841er.c | 54 +++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
diff mbox series

Patch

diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c
index 1b30cf570803..c75e63b9cfa7 100644
--- a/drivers/media/dvb-frontends/cxd2841er.c
+++ b/drivers/media/dvb-frontends/cxd2841er.c
@@ -60,6 +60,13 @@  struct cxd2841er_priv {
 	enum cxd2841er_xtal		xtal;
 	enum fe_caps caps;
 	u32				flags;
+
+	unsigned long			ber_interval;
+	unsigned long			ucb_interval;
+
+	unsigned long			ber_time;
+	unsigned long			ucb_time;
+	unsigned long			snr_time;
 };
 
 static const struct cxd2841er_cnr_data s_cn_data[] = {
@@ -1941,6 +1948,10 @@  static void cxd2841er_read_ber(struct dvb_frontend *fe)
 	struct cxd2841er_priv *priv = fe->demodulator_priv;
 	u32 ret, bit_error = 0, bit_count = 0;
 
+	if (priv->ber_time &&
+	   (!time_after(jiffies, priv->ber_time)))
+		return;
+
 	dev_dbg(&priv->i2c->dev, "%s()\n", __func__);
 	switch (p->delivery_system) {
 	case SYS_DVBC_ANNEX_A:
@@ -1978,6 +1989,19 @@  static void cxd2841er_read_ber(struct dvb_frontend *fe)
 		p->post_bit_error.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
 		p->post_bit_count.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
 	}
+
+	/*
+	 * If the per-delivery system doesn't specify, set a default timeout
+	 * that will wait for 10^7 bits or 1 second
+	 */
+	if (!priv->ber_interval && p->bandwidth_hz) {
+		priv->ber_interval = (10000000) / (p->bandwidth_hz / 1000);
+	}
+
+	if (priv->ber_interval < 1000)
+		priv->ber_interval = 1000;
+
+	priv->ber_time = jiffies + msecs_to_jiffies(priv->ber_interval);
 }
 
 static void cxd2841er_read_signal_strength(struct dvb_frontend *fe)
@@ -2037,6 +2061,13 @@  static void cxd2841er_read_snr(struct dvb_frontend *fe)
 	struct dtv_frontend_properties *p = &fe->dtv_property_cache;
 	struct cxd2841er_priv *priv = fe->demodulator_priv;
 
+	if (priv->snr_time &&
+	   (!time_after(jiffies, priv->snr_time)))
+		return;
+
+	/* Preventing asking SNR more than once per second */
+	priv->snr_time = jiffies + msecs_to_jiffies(1000);
+
 	dev_dbg(&priv->i2c->dev, "%s()\n", __func__);
 	switch (p->delivery_system) {
 	case SYS_DVBC_ANNEX_A:
@@ -2081,6 +2112,10 @@  static void cxd2841er_read_ucblocks(struct dvb_frontend *fe)
 	struct cxd2841er_priv *priv = fe->demodulator_priv;
 	u32 ucblocks = 0;
 
+	if (priv->ucb_time &&
+	   (!time_after(jiffies, priv->ucb_time)))
+		return;
+
 	dev_dbg(&priv->i2c->dev, "%s()\n", __func__);
 	switch (p->delivery_system) {
 	case SYS_DVBC_ANNEX_A:
@@ -2105,6 +2140,18 @@  static void cxd2841er_read_ucblocks(struct dvb_frontend *fe)
 
 	p->block_error.stat[0].scale = FE_SCALE_COUNTER;
 	p->block_error.stat[0].uvalue = ucblocks;
+
+	/*
+	 * If the per-delivery system doesn't specify, set a default timeout
+	 * that will wait for 100 packets or 1 second
+	 */
+	if (!priv->ucb_interval && p->bandwidth_hz)
+		priv->ucb_interval = (100 * 204 * 1000 * 8) / p->bandwidth_hz;
+
+	if (priv->ucb_interval < 1000)
+		priv->ucb_interval = 1000;
+
+	priv->ucb_time = jiffies + msecs_to_jiffies(priv->ucb_interval);
 }
 
 static int cxd2841er_dvbt2_set_profile(
@@ -3360,6 +3407,13 @@  static int cxd2841er_set_frontend_s(struct dvb_frontend *fe)
 	p->post_bit_error.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
 	p->post_bit_count.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
 
+	/* Reset the wait for jiffies logic */
+	priv->ber_interval = 0;
+	priv->ucb_interval = 0;
+	priv->ber_time = 0;
+	priv->ucb_time = 0;
+	priv->snr_time = 0;
+
 	return ret;
 }