[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>

1 files changed, 17 insertions, 7 deletions

diff --git a/drivers/media/dvb-frontends/mb86a20s.c b/drivers/media/dvb-frontends/mb86a20s.c
index 0fbfae23d904..9948fcbf1596 100644
--- 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*/