[media] mb86a20s: don't allow updating signal strength too fast

Getting signal strength requires some loop poking with I2C.
Don't let it happen too fast.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/dvb-frontends/mb86a20s.c b/drivers/media/dvb-frontends/mb86a20s.c
index 0fbfae2..9948fcb 100644 (file)
--- a/drivers/media/dvb-frontends/mb86a20s.c
+++ b/drivers/media/dvb-frontends/mb86a20s.c
@@ -34,6 +34,7 @@ struct mb86a20s_state {
        u32 if_freq;
 
        u32 estimated_rate[3];
+       unsigned long get_strength_time;
 
        bool need_init;
 };
@@ -318,9 +319,17 @@ static int mb86a20s_read_status(struct dvb_frontend *fe, fe_status_t *status)
 static int mb86a20s_read_signal_strength(struct dvb_frontend *fe)
 {
        struct mb86a20s_state *state = fe->demodulator_priv;
+       struct dtv_frontend_properties *c = &fe->dtv_property_cache;
        int rc;
        unsigned rf_max, rf_min, rf;
 
+       if (state->get_strength_time &&
+          (!time_after(jiffies, state->get_strength_time)))
+               return c->strength.stat[0].uvalue;
+
+       /* Reset its value if an error happen */
+       c->strength.stat[0].uvalue = 0;
+
        /* Does a binary search to get RF strength */
        rf_max = 0xfff;
        rf_min = 0;
@@ -350,15 +359,19 @@ static int mb86a20s_read_signal_strength(struct dvb_frontend *fe)
                        rf = (rf_max + rf_min) / 2;
 
                        /* Rescale it from 2^12 (4096) to 2^16 */
-                       rf <<= (16 - 12);
+                       rf = rf << (16 - 12);
+                       if (rf)
+                               rf |= (1 << 12) - 1;
+
                        dev_dbg(&state->i2c->dev,
                                "%s: signal strength = %d (%d < RF=%d < %d)\n",
                                __func__, rf, rf_min, rf >> 4, rf_max);
-                       return rf;
+                       c->strength.stat[0].uvalue = rf;
+                       state->get_strength_time = jiffies +
+                                                  msecs_to_jiffies(1000);
+                       return 0;
                }
        } while (1);
-
-       return 0;
 }
 
 static int mb86a20s_get_modulation(struct mb86a20s_state *state,
@@ -1882,7 +1895,6 @@ static int mb86a20s_read_status_and_stats(struct dvb_frontend *fe,
                                          fe_status_t *status)
 {
        struct mb86a20s_state *state = fe->demodulator_priv;
-       struct dtv_frontend_properties *c = &fe->dtv_property_cache;
        int rc, status_nr;
 
        dev_dbg(&state->i2c->dev, "%s called.\n", __func__);
@@ -1913,8 +1925,6 @@ static int mb86a20s_read_status_and_stats(struct dvb_frontend *fe,
                rc = 0;         /* Status is OK */
                goto error;
        }
-       /* Fill signal strength */
-       c->strength.stat[0].uvalue = rc;
 
        if (status_nr >= 7) {
                /* Get TMCC info*/