[PATCH] dvb: frontend: mt352: fix signal strength reading

Fix two problems with the signal strength value in the mt352.c frontend:
1. the 4 most significant bits are zeroed - shift and mask wrong way round
2. need to align the 12 bits from the registers at the top of the 16 bit
   returned value - otherwise the range is not 0 to 0xffff its 0xf000 to 0xffff

Signed-off-by: Barry Scott <barry.scott@onelan.co.uk>
Signed-off-by: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/media/dvb/frontends/mt352.c b/drivers/media/dvb/frontends/mt352.c
index d32dc4de9e7f..cc1bc0edd65e 100644
--- a/drivers/media/dvb/frontends/mt352.c
+++ b/drivers/media/dvb/frontends/mt352.c
@@ -462,9 +462,11 @@ static int mt352_read_signal_strength(struct dvb_frontend* fe, u16* strength)
 {
         struct mt352_state* state = fe->demodulator_priv;
 
-        u16 signal = ((mt352_read_register(state, AGC_GAIN_1) << 8) & 0x0f) |
-                      (mt352_read_register(state, AGC_GAIN_0));
+        /* align the 12 bit AGC gain with the most significant bits */
+        u16 signal = ((mt352_read_register(state, AGC_GAIN_1) & 0x0f) << 12) |
+                (mt352_read_register(state, AGC_GAIN_0) << 4);
 
+        /* inverse of gain is signal strength */
         *strength = ~signal;
         return 0;
 }