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From: "nibble.max" <nibble.max@gmail.com>
To: "Antti Palosaari" <crope@iki.fi>
Cc: "linux-media" <linux-media@vger.kernel.org>,
	"olli.salonen" <olli.salonen@iki.fi>
Subject: [PATCH] m88ts2022: fix high symbol rate transponders missing on 32bit platform.
Date: Sat, 16 Aug 2014 14:12:32 +0800	[thread overview]
Message-ID: <201408161412275930052@gmail.com> (raw)

The current m88ts2022 driver will miss the following high symbol rate transponders on Telstar 18 138.0.
12385 H 43200, 
12690 H 43200,
12538 V 41250...
the code for f_3db_hz will overflow for the high symbol rate.
for example, symbol rate=41250 KS/s
symbol_rate * 135UL = 5568750000(1 4BEC 61B0), the value is larger than unsigned int on 32bit platform. 
that makes the wrong result.
Exchanging the div and mul position fixs it.

Signed-off-by: Nibble Max <nibble.max@gmail.com>
---
 drivers/media/tuners/m88ts2022.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/tuners/m88ts2022.c b/drivers/media/tuners/m88ts2022.c
index 40c42de..65c8acc 100644
--- a/drivers/media/tuners/m88ts2022.c
+++ b/drivers/media/tuners/m88ts2022.c
@@ -314,7 +314,7 @@ static int m88ts2022_set_params(struct dvb_frontend *fe)
 	div_min = gdiv28 * 78 / 100;
 	div_max = clamp_val(div_max, 0U, 63U);
 
-	f_3db_hz = c->symbol_rate * 135UL / 200UL;
+	f_3db_hz = (c->symbol_rate / 200UL) * 135UL;
 	f_3db_hz +=  2000000U + (frequency_offset_khz * 1000U);
 	f_3db_hz = clamp(f_3db_hz, 7000000U, 40000000U);

-- 
1.9.1


             reply	other threads:[~2014-08-16  6:13 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-16  6:12 nibble.max [this message]
2014-08-16 12:38 ` [PATCH] m88ts2022: fix high symbol rate transponders missing on 32bit platform Mauro Carvalho Chehab
2014-08-16 12:53   ` Antti Palosaari
2014-08-16 19:26     ` Matthias Schwarzott
2014-08-16 13:31 ` Re: [PATCH] m88ts2022: fix high symbol rate transponders missing on32bit platform Max Xiang
  -- strict thread matches above, loose matches on Subject: below --
2014-08-16  6:26 [PATCH] m88ts2022: fix high symbol rate transponders missing on 32bit platform nibble.max

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