[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>

1 files changed, 27 insertions, 3 deletions

diff --git a/drivers/media/tuners/r820t.c b/drivers/media/tuners/r820t.c
index 7e02920f385a..ed9cd6569548 100644
--- 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;
 }