[media] r820t: Give a better estimation of the signal strength

Instead of a binary signal strength measure, use the tuner gain
to obtain a better estimation of the signal strength.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: Antti Palosaari <crope@iki.fi>

diff --git a/drivers/media/tuners/r820t.c b/drivers/media/tuners/r820t.c
index 7e02920..ed9cd65 100644 (file)
--- a/drivers/media/tuners/r820t.c
+++ b/drivers/media/tuners/r820t.c
@@ -1082,6 +1082,18 @@ static int r820t_set_tv_standard(struct r820t_priv *priv,
        return 0;
 }
 
+static int r820t_read_gain(struct r820t_priv *priv)
+{
+       u8 data[4];
+       int rc;
+
+       rc = r820_read(priv, 0x00, data, sizeof(data));
+       if (rc < 0)
+               return rc;
+
+       return ((data[3] & 0x0f) << 1) + ((data[3] & 0xf0) >> 4);
+}
+
 static int generic_set_freq(struct dvb_frontend *fe,
                            u32 freq /* in HZ */,
                            unsigned bw,
@@ -1353,11 +1365,23 @@ static int r820t_set_params(struct dvb_frontend *fe)
 static int r820t_signal(struct dvb_frontend *fe, u16 *strength)
 {
        struct r820t_priv *priv = fe->tuner_priv;
+       int rc = 0;
 
-       if (priv->has_lock)
-               *strength = 0xffff;
-       else
+       if (priv->has_lock) {
+               rc = r820t_read_gain(priv);
+               if (rc < 0)
+                       return rc;
+
+               /* A higher gain at LNA means a lower signal strength */
+               *strength = (45 - rc) << 4 | 0xff;
+       } else {
                *strength = 0;
+       }
+
+       tuner_dbg("%s: %s, gain=%d strength=%d\n",
+                 __func__,
+                 priv->has_lock ? "PLL locked" : "no signal",
+                 rc, *strength);
 
        return 0;
 }