display,fb: Clear framebuffer early in the Sonoma stage2 fixup path

stage1 ends up with an ugly Asahi 100% logo on top of a 200% Apple logo.
Let's just clear it so it looks nicer.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

src/display.c

@@ -546,6 +546,7 @@ int display_init(void)
         return display_configure(NULL);
     } else if (!(cur_boot_args.video.depth & FB_DEPTH_FLAG_RETINA)) {
         printf("display: Internal display with non-retina flag, assuming Sonoma bug and reconfiguring\n");
+        fb_clear_direct(); // Old m1n1 stage1 ends up with an ugly logo situation, clear it.
         return display_configure(NULL);
     } else {
         printf("display: Display is already initialized (%ldx%ld)\n", cur_boot_args.video.width,

src/fb.c

@@ -325,6 +325,16 @@ static void fb_clear_console(void)
     fb_update();
 }
 
+void fb_clear_direct(void)
+{
+    size_t fb_size = cur_boot_args.video.stride * cur_boot_args.video.height;
+
+    mmu_add_mapping(cur_boot_args.video.base, cur_boot_args.video.base, ALIGN_UP(fb_size, 0x4000),
+                    MAIR_IDX_NORMAL_NC, PERM_RW);
+
+    memset64((void *)cur_boot_args.video.base, 0, fb_size);
+}
+
 void fb_init(bool clear)
 {
     fb.hwptr = (void *)cur_boot_args.video.base;

src/fb.h

@@ -45,6 +45,7 @@ void fb_blit(u32 x, u32 y, u32 w, u32 h, void *data, u32 stride, pix_fmt_t forma
 void fb_unblit(u32 x, u32 y, u32 w, u32 h, void *data, u32 stride);
 void fb_fill(u32 x, u32 y, u32 w, u32 h, rgb_t color);
 void fb_clear(rgb_t color);
+void fb_clear_direct(void);
 
 void fb_display_logo(void);
 void fb_restore_logo(void);