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author | Seth Barry <seth@cyberseth.com> | 2009-09-27 19:42:29 (GMT) |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2009-11-07 14:55:04 (GMT) |
commit | a57c1dcb93e43357ed3f666e5a2b5d5071dd3930 (patch) | |
tree | fef7cbe62f97fdcea7ff36cbc1e995bdfc617866 /drivers/media | |
parent | 4d8317876d5f53ef792e90f89d8f162d7bca5c81 (diff) | |
download | linux-fsl-qoriq-a57c1dcb93e43357ed3f666e5a2b5d5071dd3930.tar.xz |
V4L/DVB (13109): tda18271: fix signedness issue in tda18271_rf_tracking_filters_init
While having tda18271 module set with debug=17 (cal & info prints) and
cal=0 (delay calibration process until first use) - I discovered that
during the calibration process, if the frequency test for 69750000
returned a bcal of 0 (see tda18721-fe.c in tda18271_powerscan func) that
the tuner wouldn't be able to pickup any of the frequencies in the range
(all the other frequencies bands returned bcal=1). I spent some time
going over the code and the NXP's tda18271 spec (ver.4 of it i think) and
adding a lot of debug prints and walking/stepping through the calibration
process. I found that when the powerscan fails to find a frequency, the
rf calibration is not run and the default value is supposed to be used in
its place (pulled from the RF_CAL_map table) - but something was getting
goofed up there.
Now, my c coding skills are very rusty, but i think root of the problem is
a signedness issue with the math operation for calculating the rf_a1 and
rf_a2 values in tda18271_rf_tracking_filters_init func, which results in
values like 20648 for rf_a1 (when it should probably have a value like 0,
or so slightly negative that it should be zero - this bad value for rf_a1
would in turn makes the approx calc within
tda18271c2_rf_tracking_filters_correction go out of whack). The simplest
solution i found was to explicitly convert the signedness of the
denominator to avoid the implicit conversion. The values placed into the
u32 rf_freq array should never exceed about 900mhz, so i think the s32 max
value shouldn't be an issue in this case.
I've tested it out a little, and even when i get a bcal=0 with the
modified code, the default calibration value gets used, rf_a1 is zero, and
the tuner seems to lock on the stream and mythtv seems to play it fine.
Signed-off-by: Seth Barry <seth@cyberseth.com>
Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
CC: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media')
-rw-r--r-- | drivers/media/common/tuners/tda18271-fe.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/media/common/tuners/tda18271-fe.c b/drivers/media/common/tuners/tda18271-fe.c index cccaf16..3a50ce9 100644 --- a/drivers/media/common/tuners/tda18271-fe.c +++ b/drivers/media/common/tuners/tda18271-fe.c @@ -616,13 +616,13 @@ static int tda18271_rf_tracking_filters_init(struct dvb_frontend *fe, u32 freq) case RF2: map[i].rf_a1 = (prog_cal[RF2] - prog_tab[RF2] - prog_cal[RF1] + prog_tab[RF1]) / - ((rf_freq[RF2] - rf_freq[RF1]) / 1000); + (s32)((rf_freq[RF2] - rf_freq[RF1]) / 1000); map[i].rf2 = rf_freq[RF2] / 1000; break; case RF3: map[i].rf_a2 = (prog_cal[RF3] - prog_tab[RF3] - prog_cal[RF2] + prog_tab[RF2]) / - ((rf_freq[RF3] - rf_freq[RF2]) / 1000); + (s32)((rf_freq[RF3] - rf_freq[RF2]) / 1000); map[i].rf_b2 = prog_cal[RF2] - prog_tab[RF2]; map[i].rf3 = rf_freq[RF3] / 1000; break; |