tuner_fc001x: check if PLL values are within boundaries

This fixes the issue of the FC0013 locking up at frequencies
between 928.0 and 950.0 MHz, which happened because
the numerator of the fraction exceeded its 5 bit limit.
For the tuner to behave normally again, the dongle needed
to be replugged.

For the FC0013 this now results in a small gap between
948.6 MHz and 950.0 MHz, where no valid PLL values
are existant.

For the FC0012 tuning is aborted when the maximum
frequency has been reached (948.6 MHz).

Signed-off-by: Steve Markgraf <steve@steve-m.de>

src/tuner_fc0012.c

@@ -22,6 +22,7 @@
  */
 
 #include <stdint.h>
+#include <stdio.h>
 
 #include "rtlsdr_i2c.h"
 #include "tuner_fc0012.h"
@@ -215,12 +216,23 @@ int fc0012_set_params(void *dev, uint32_t freq, uint32_t bandwidth)
 		am = (uint8_t)(xdiv - (8 * pm));
 
 		if (am < 2) {
-			reg[1] = am + 8;
-			reg[2] = pm - 1;
+			am += 8;
+			pm--;
+		}
+
+		if (pm > 31) {
+			reg[1] = am + (8 * (pm - 31));
+			reg[2] = 31;
 		} else {
 			reg[1] = am;
 			reg[2] = pm;
 		}
+
+		if (reg[1] > 15) {
+			fprintf(stderr, "[FC0012] no valid PLL combination "
+					"found for %u Hz!\n", freq);
+			return -1;
+		}
 	} else {
 		/* fix for frequency less than 45 MHz */
 		reg[1] = 0x06;

src/tuner_fc0013.c

@@ -25,6 +25,7 @@
  */
 
 #include <stdint.h>
+#include <stdio.h>
 
 #include "rtlsdr_i2c.h"
 #include "tuner_fc0013.h"
@@ -320,12 +321,23 @@ int fc0013_set_params(void *dev, uint32_t freq, uint32_t bandwidth)
 		am = (uint8_t)(xdiv - (8 * pm));
 
 		if (am < 2) {
-			reg[1] = am + 8;
-			reg[2] = pm - 1;
+			am += 8;
+			pm--;
+		}
+
+		if (pm > 31) {
+			reg[1] = am + (8 * (pm - 31));
+			reg[2] = 31;
 		} else {
 			reg[1] = am;
 			reg[2] = pm;
 		}
+
+		if (reg[1] > 15) {
+			fprintf(stderr, "[FC0013] no valid PLL combination "
+					"found for %u Hz!\n", freq);
+			return -1;
+		}
 	} else {
 		/* fix for frequency less than 45 MHz */
 		reg[1] = 0x06;