From 4ff4ac1beae58a2fea7ec2ad43d6c3b60d90ec61 Mon Sep 17 00:00:00 2001
From: Barry Scott <barry.scott@onelan.co.uk>
Date: Fri, 9 Sep 2005 13:02:29 -0700
Subject: [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>
---
 drivers/media/dvb/frontends/mt352.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'drivers/media/dvb/frontends')

diff --git a/drivers/media/dvb/frontends/mt352.c b/drivers/media/dvb/frontends/mt352.c
index d32dc4de9e7..cc1bc0edd65 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;
 }
-- 
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