Extended clock calibration to correctly handle 624-line non-interlaced modes

Change-Id: I6aaf957512e0f9d77df89d835f8cf40b4d801506

src/defs.h

@@ -30,4 +30,6 @@
 #define CSYNC_MASK    (1 << CSYNC_PIN)
 #define MODE7_MASK    (1 << MODE7_PIN)
 
+#define INTERLACED_FLAG (1 << 31)
+
 #endif

src/rgb_to_fb.S

@@ -1,9 +1,6 @@
 #include "rpi-base.h"
 #include "defs.h"
 
-// TODO:
-// - calibration gives incorrect result in non-interlaced modes
-
 .text
 .global rgb_to_fb
 .global measure_vsync
@@ -307,26 +304,42 @@ measure_vsync:
         // Initialize the cycle counter, and set r4=GPLEV0
         bl     init_timer_and_io
         
-        // wait for vsync, r6 contains the time of the subsequenct hsync rising edge
+        // wait for vsync, r6 contains the time of the subsequent hsync rising edge
         bl     wait_for_vsync
         mov    r0, r6
 
-        // Wait for a complete frame
+        // Wait for a first field of frame
         bl     wait_for_vsync
+
+        // Record field type
+        sub    r6, r6, r7
+        cmp    r6, #32768
+        movlt  r3, #0         // Odd
+        movge  r3, #1         // Even
+
+        // Wait for a second field of frame
         bl     wait_for_vsync
 
         // Return the time for a complete frame (should be 40ms)
         sub    r0, r6, r0
+
+        // Test for non-interlaced by looking for two successive fields of the same type
+        sub    r6, r6, r7
+        cmp    r6, #32768        
+        eorlt  r3, r3, #1     // Odd
+        tst    r3, #1
+        // Set bit 31 of result if frame was interlaced
+        orreq  r0, r0, #INTERLACED_FLAG
         
         pop    {r4-r12, lr}
         mov    pc, lr
         
 clear_screen:
-        mov    r11, r0           // r0 is the start of the frame buffer
+        mov    r11, r0        // r0 is the start of the frame buffer
         mov    r7, #0
-        mov    r5, #512          // fixed 512 lines
+        mov    r5, #512       // fixed 512 lines
 clear_loop1:
-        mov    r6, r2            // r2 is bytes per line
+        mov    r6, r2         // r2 is bytes per line
 clear_loop2:
         str    r7, [r11], #4
         subs   r6, r6, #4

src/rgb_to_hdmi.c

@@ -199,16 +199,28 @@ int delay;
 
 int calibrate_clock() {
    int a = 13;
-   log_info("Nominal clock = %d", CORE_FREQ);
+   unsigned int frame_ref;
 
-   int frame_time = measure_vsync();
-   log_info("   Frame time = %dns", frame_time);
+   log_info("     Nominal clock = %d Hz", CORE_FREQ);
 
-   double error = (double) frame_time / (double) 40000000;
-   log_info("  Frame error = %d PPM", (int) ((error - 1.0) * 1e6));
+   unsigned int frame_time = measure_vsync();
+
+   if (frame_time & INTERLACED_FLAG) {
+      frame_ref = 40000000;
+      log_info("Nominal frame time = %d ns (interlaced)", frame_ref);
+   } else {
+      frame_ref = 40000000 - 64000;
+      log_info("Nominal frame time = %d ns (non-interlaced)", frame_ref);
+   }
+   frame_time &= ~INTERLACED_FLAG;
+
+   log_info(" Actual frame time = %d ns", frame_time);
+
+   double error = (double) frame_time / (double) frame_ref;
+   log_info("  Frame time error = %d PPM", (int) ((error - 1.0) * 1e6));
 
    int new_clock = (int) (((double) CORE_FREQ) / error);
-   log_info("  Ideal clock = %d", new_clock);
+   log_info("     Optimal clock = %d Hz", new_clock);
 
    // Sanity check clock
    if (new_clock < 380000000 || new_clock > 388000000) {
@@ -231,7 +243,7 @@ int calibrate_clock() {
 
    // Check the new clock
    int actual_clock = get_clock_rate(CORE_CLK_ID);
-   log_info("    New clock = %d", actual_clock);
+   log_info("       Final clock = %d Hz", actual_clock);
 
    return a;
 }