Make vsync polarity detection switchable

src/defs.h

@@ -550,7 +550,8 @@ typedef struct {
 #define  VSYNC_NONINTERLACED           3
 #define  VSYNC_NONINTERLACED_DEJITTER  4
 #define  VSYNC_BLANKING                5
-#define  NUM_VSYNC                     6
+#define  VSYNC_POLARITY                6
+#define  NUM_VSYNC                     7
 
 #define  VIDEO_PROGRESSIVE 0
 #define  VIDEO_INTERLACED  1

src/geometry.c

@@ -32,7 +32,8 @@ static const char *vsync_names[] = {
    "Interlaced 160uS Vsync",
    "Non Interlaced",
    "Flywheel",
-   "Blanking"
+   "Blanking",
+   "Polarity"
 };
 
 static const char *setup_names[] = {

src/rgb_to_fb.S

@@ -409,6 +409,7 @@ buffer_chosen:
         bic    r3, r3, #BIT_ELK         // clear elk mode
         ldr    r8, param_vsync_type
         cmp    r8, #VSYNC_AUTO
+        cmpne  r8, #VSYNC_POLARITY
         beq    auto_detect_vsync
         cmp    r8, #VSYNC_INTERLACED_160  // interlaced half line
         orreq  r3, r3, #BIT_ELK
@@ -1153,6 +1154,10 @@ done_ntsc_auto:
         tst    r8, #SYNC_BIT_COMPOSITE_SYNC       //set if composite so don't check vsync polarity
         bne    skip_sync_time_test
 
+        ldr    r8, param_vsync_type
+        cmp    r8, #VSYNC_POLARITY
+        bne    skip_sync_time_test
+
         orr    r0, #RET_VSYNC_POLARITY_CHANGED
 
         mov    r8, #VERSION_MASK