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authorTrent Piepho <xyzzy@speakeasy.org>2007-10-01 00:32:25 -0300
committerMauro Carvalho Chehab <mchehab@infradead.org>2007-10-09 22:14:50 -0300
commit857e594ad5662349d95ad33f987cbf55cc356a90 (patch)
treed5ad5fdc83564008dba1644adff48c4a1e95903a
parent4753647e6422341a091e729b9d81a9a5e7fe6179 (diff)
V4L/DVB (6245): GemTek Radio card - frequency calculation
Frequency calculation to use better math. It's still the same IF offset and step size (which are not the same as the datasheet says) as the code was before. It's just more efficient and accurate. Signed-off-by: Trent Piepho <xyzzy@speakeasy.org> Reviewed-by: Pekka Seppänen <pexu@kapsi.fi> Signed-off-by: Douglas Schilling Landgraf <dougsland@gmail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
-rw-r--r--drivers/media/radio/radio-gemtek.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/drivers/media/radio/radio-gemtek.c b/drivers/media/radio/radio-gemtek.c
index f959bb71c46..0fcd2b09218 100644
--- a/drivers/media/radio/radio-gemtek.c
+++ b/drivers/media/radio/radio-gemtek.c
@@ -89,6 +89,14 @@ module_param(radio_nr, int, 0444);
#define GEMTEK_LOWFREQ (87*16000)
#define GEMTEK_HIGHFREQ (108*16000)
+/*
+ * Frequency calculation constants. Intermediate frequency 10.52 MHz (nominal
+ * value 10.7 MHz), reference divisor 6.39 kHz (nominal 6.25 kHz).
+ */
+#define FSCALE 8
+#define IF_OFFSET ((unsigned int)(10.52 * 16000 * (1<<FSCALE)))
+#define REF_FREQ ((unsigned int)(6.39 * 16 * (1<<FSCALE)))
+
#define GEMTEK_CK 0x01 /* Clock signal */
#define GEMTEK_DA 0x02 /* Serial data */
#define GEMTEK_CE 0x04 /* Chip enable */
@@ -219,14 +227,11 @@ static void gemtek_bu2614_transmit(struct gemtek_device *dev)
}
/*
- * Convert FM-frequency for BU2614FS (3.125 KHz STDF expected).
+ * Calculate divisor from FM-frequency for BU2614FS (3.125 KHz STDF expected).
*/
-static inline void gemtek_convfreq(unsigned long *freq)
+static unsigned long gemtek_convfreq(unsigned long freq)
{
- (*freq) /= 160;
- (*freq) += 1052; /* FMIN, 10.52 MHz */
- (*freq) *= 1565; /* STDF, 1 / 156.5 = 0.00639 */
- (*freq) /= 1000;
+ return ((freq<<FSCALE) + IF_OFFSET + REF_FREQ/2) / REF_FREQ;
}
/*
@@ -253,10 +258,8 @@ static void gemtek_setfreq(struct gemtek_device *dev, unsigned long freq)
gemtek_bu2614_set(dev, BU2614_FMUN, 1); /* GT bit set */
gemtek_bu2614_set(dev, BU2614_TEST, 0);
- gemtek_convfreq(&freq);
-
gemtek_bu2614_set(dev, BU2614_STDF, GEMTEK_STDF_3_125_KHZ);
- gemtek_bu2614_set(dev, BU2614_FREQ, freq);
+ gemtek_bu2614_set(dev, BU2614_FREQ, gemtek_convfreq(freq));
gemtek_bu2614_transmit(dev);
}