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Subject: media: mb86a20s: make the bit rate estimation function more generic
Author: Mauro Carvalho Chehab <mchehab+sams...@kernel.org>
Date: Fri Oct 4 08:42:47 2019 -0300
While 99% of the implementation of the bitrate estimation
routine for ISDB-T is generic, the current approach mangles it
with some mb86a20s-specific thing.
Split the calculus from the specific stuff, in order to make
easier to use the same approach on other drivers requiring
a similar formula.
Signed-off-by: Mauro Carvalho Chehab <mchehab+sams...@kernel.org>
Signed-off-by: Sean Young <s...@mess.org>
drivers/media/dvb-frontends/mb86a20s.c | 54 +++++++++++++++-------------------
1 file changed, 23 insertions(+), 31 deletions(-)
---
diff --git a/drivers/media/dvb-frontends/mb86a20s.c
b/drivers/media/dvb-frontends/mb86a20s.c
index 4e50441c247a..a7faf0cf8788 100644
--- a/drivers/media/dvb-frontends/mb86a20s.c
+++ b/drivers/media/dvb-frontends/mb86a20s.c
@@ -517,7 +517,7 @@ static void mb86a20s_reset_frontend_cache(struct
dvb_frontend *fe)
* Estimates the bit rate using the per-segment bit rate given by
* ABNT/NBR 15601 spec (table 4).
*/
-static u32 isdbt_rate[3][5][4] = {
+static const u32 isdbt_rate[3][5][4] = {
{ /* DQPSK/QPSK */
{ 280850, 312060, 330420, 340430 }, /* 1/2 */
{ 374470, 416080, 440560, 453910 }, /* 2/3 */
@@ -539,13 +539,9 @@ static u32 isdbt_rate[3][5][4] = {
}
};
-static void mb86a20s_layer_bitrate(struct dvb_frontend *fe, u32 layer,
- u32 modulation, u32 forward_error_correction,
- u32 guard_interval,
- u32 segment)
+static u32 isdbt_layer_min_bitrate(struct dtv_frontend_properties *c,
+ u32 layer)
{
- struct mb86a20s_state *state = fe->demodulator_priv;
- u32 rate;
int mod, fec, guard;
/*
@@ -553,7 +549,7 @@ static void mb86a20s_layer_bitrate(struct dvb_frontend *fe,
u32 layer,
* to consider the lowest bit rate, to avoid taking too long time
* to get BER.
*/
- switch (modulation) {
+ switch (c->layer[layer].modulation) {
case DQPSK:
case QPSK:
default:
@@ -567,7 +563,7 @@ static void mb86a20s_layer_bitrate(struct dvb_frontend *fe,
u32 layer,
break;
}
- switch (forward_error_correction) {
+ switch (c->layer[layer].fec) {
default:
case FEC_1_2:
case FEC_AUTO:
@@ -587,7 +583,7 @@ static void mb86a20s_layer_bitrate(struct dvb_frontend *fe,
u32 layer,
break;
}
- switch (guard_interval) {
+ switch (c->guard_interval) {
default:
case GUARD_INTERVAL_1_4:
guard = 0;
@@ -603,29 +599,14 @@ static void mb86a20s_layer_bitrate(struct dvb_frontend
*fe, u32 layer,
break;
}
- /* Samples BER at BER_SAMPLING_RATE seconds */
- rate = isdbt_rate[mod][fec][guard] * segment * BER_SAMPLING_RATE;
-
- /* Avoids sampling too quickly or to overflow the register */
- if (rate < 256)
- rate = 256;
- else if (rate > (1 << 24) - 1)
- rate = (1 << 24) - 1;
-
- dev_dbg(&state->i2c->dev,
- "%s: layer %c bitrate: %d kbps; counter = %d (0x%06x)\n",
- __func__, 'A' + layer,
- segment * isdbt_rate[mod][fec][guard]/1000,
- rate, rate);
-
- state->estimated_rate[layer] = rate;
+ return isdbt_rate[mod][fec][guard] * c->layer[layer].segment_count;
}
static int mb86a20s_get_frontend(struct dvb_frontend *fe)
{
struct mb86a20s_state *state = fe->demodulator_priv;
struct dtv_frontend_properties *c = &fe->dtv_property_cache;
- int layer, rc;
+ int layer, rc, rate, counter;
dev_dbg(&state->i2c->dev, "%s called.\n", __func__);
@@ -676,10 +657,21 @@ static int mb86a20s_get_frontend(struct dvb_frontend *fe)
dev_dbg(&state->i2c->dev, "%s: interleaving %d.\n",
__func__, rc);
c->layer[layer].interleaving = rc;
- mb86a20s_layer_bitrate(fe, layer, c->layer[layer].modulation,
- c->layer[layer].fec,
- c->guard_interval,
- c->layer[layer].segment_count);
+
+ rate = isdbt_layer_min_bitrate(c, layer);
+ counter = rate * BER_SAMPLING_RATE;
+
+ /* Avoids sampling too quickly or to overflow the register */
+ if (counter < 256)
+ counter = 256;
+ else if (counter > (1 << 24) - 1)
+ counter = (1 << 24) - 1;
+
+ dev_dbg(&state->i2c->dev,
+ "%s: layer %c bitrate: %d kbps; counter = %d
(0x%06x)\n",
+ __func__, 'A' + layer, rate / 1000, counter, counter);
+
+ state->estimated_rate[layer] = counter;
}
rc = mb86a20s_writereg(state, 0x6d, 0x84);
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