From 08d09e678f942fef9e9efc9a88e62f0b4e7bb0a4 Mon Sep 17 00:00:00 2001
From: Michael Sevakis <jethead71@rockbox.org>
Date: Tue, 22 Jun 2010 07:27:34 +0000
Subject: [PATCH] Sanyo lv24020lp FM: Improve frequency measurement on PP thus
 improving  initial frequency setting. Properly account for IF when tuning FM
 oscillator (this worked poorly before but appears to work as expected now --
 aka. works for me). Not sure what this will do to iAudio7 or Cowon D2 but if
 they can implement a good duration measurement, they should do so or use the
 internal timer if possible.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27042 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/drivers/tuner/lv24020lp.c | 32 +++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/firmware/drivers/tuner/lv24020lp.c b/firmware/drivers/tuner/lv24020lp.c
index a53d93bf65..86f8c39593 100644
--- a/firmware/drivers/tuner/lv24020lp.c
+++ b/firmware/drivers/tuner/lv24020lp.c
@@ -496,9 +496,25 @@ static int tuner_measure(unsigned char type, int scale, int duration)
 
     /* start counter, delay for specified time and stop it */
     lv24020lp_write_set(CNT_CTRL, CNT_EN);
-    udelay(duration*1000 - 16);
+
+#ifdef CPU_PP
+    /* obtain actual duration, including interrupts that occurred and
+     * the time to write the counter stop */
+    long usec = USEC_TIMER;
+#endif
+
+    udelay(duration*1000);
+
     lv24020lp_write_clear(CNT_CTRL, CNT_EN);
 
+#ifdef CPU_PP
+    duration = (USEC_TIMER - usec) / 1000;
+#endif
+
+    /* This function takes a loooong time and other stuff needs
+       running by now */
+    yield();
+
     /* read tick count */
     finval = (lv24020lp_read(CNT_H) << 8) | lv24020lp_read(CNT_L);
 
@@ -512,10 +528,6 @@ static int tuner_measure(unsigned char type, int scale, int duration)
     else
         finval = scale*finval / duration;
 
-    /* This function takes a loooong time and other stuff needs
-       running by now */
-    yield();
-
     return (int)finval;
 }
 
@@ -532,6 +544,16 @@ static void set_frequency(int freq)
 
     enable_afc(false);
 
+    /* For the LV2400x, the tuned frequency is the sum of the displayed
+     * frequency and the preset IF frequency, in formula:
+     *      Tuned FM frequency = displayed frequency + preset IF frequency
+     *
+     * For example: when the IF frequency of LV2400x is preset at 110 kHz,
+     * it must be tuned at 88.51 MHz to receive the radio station at 88.4 MHz.
+     * -- AN2400S04@ – V0.4
+     */
+    freq += if_set;
+
     /* MHz -> kHz */
     freq /= 1000;