From 828beb45bd7f9739a819d21f55b891f2e45550fc Mon Sep 17 00:00:00 2001
From: Aaron Lindsay <aaron@aclindsay.com>
Date: Sat, 6 Oct 2012 18:54:37 -0400
Subject: [PATCH] Raspberry Pi VideoCore: Wait for framebuffer address if not
 available

Sometimes the VideoCore does not immediately provide the framebuffer
address, even after it has returned success via a mailbox read.
---
 drivers/bcm2835_videocore.c | 38 ++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/bcm2835_videocore.c b/drivers/bcm2835_videocore.c
index 8cbda3c..460cc37 100644
--- a/drivers/bcm2835_videocore.c
+++ b/drivers/bcm2835_videocore.c
@@ -25,16 +25,16 @@
 #include <drivers/bcm2835_mailbox.h>
 
 struct bcm2835_config {
-	uint32 width;
-	uint32 height;
-	uint32 vwidth;
-	uint32 vheight;
-	uint32 pitch;
-	uint32 color_depth;
-	uint32 xoffset;
-	uint32 yoffset;
-	uint32 fb_base_addr;
-	uint32 size;
+	volatile uint32 width;
+	volatile uint32 height;
+	volatile uint32 vwidth;
+	volatile uint32 vheight;
+	volatile uint32 pitch;
+	volatile uint32 color_depth;
+	volatile uint32 xoffset;
+	volatile uint32 yoffset;
+	volatile uint32 fb_base_addr;
+	volatile uint32 size;
 };
 
 #define MAILBOX_BUFFER_SIZE (32*4*2)
@@ -75,11 +75,27 @@ int bcm2835_videocore_init(struct fb *f, unsigned int color_depth) {
 	mailbox_write(MBOX_FB, (uint32)cfg);
 	result = mailbox_read(MBOX_FB);
 
-	if (result || !cfg->fb_base_addr) {
+	if (result) {
 		print("Error: did not request a proper framebuffer\n");
 		return -1;
 	}
 
+	if (!cfg->fb_base_addr) {
+		int i;
+		print("BCM2835 VideoCore returned success from framebuffer "
+				"setup mailbox call, but framebuffer address is "
+				"not yet available. Waiting...\n");
+		for (i = 0; i < 1<<30 && !cfg->fb_base_addr; i++);
+
+		if (!cfg->fb_base_addr) {
+
+			print("Error: VideoCore did not provide framebuffer "
+					"base address.\n");
+			return -1;
+		}
+		print("VideoCore provided framebuffer base address after %d loops.\n", i);
+	}
+
 	f->device = &bcm2835_fb_device;
 	f->device->fbaddr = (void*)cfg->fb_base_addr;
 	f->width = cfg->width;