ARM: 9216/1: Fix MAX_DMA_ADDRESS overflow

Commit 26f09e9b ("mm/memblock: add memblock memory allocation apis")
added a check to determine whether arm_dma_zone_size is exceeding the
amount of kernel virtual address space available between the upper 4GB
virtual address limit and PAGE_OFFSET in order to provide a suitable
definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
address space. The quantity used for comparison was off by a missing
trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
quantity.

This was caught thanks to CONFIG_DEBUG_VIRTUAL on the bcm2711 platform
where we define a dma_zone_size of 1GB and we have a PAGE_OFFSET value
of 0xc000_0000 (CONFIG_VMSPLIT_3G) leading to MAX_DMA_ADDRESS being
0x1_0000_0000 which overflows the unsigned long type used throughout
__pa() and then __virt_addr_valid(). Because the virtual address passed
to __virt_addr_valid() would now be 0, the function would loudly warn
and flood the kernel log, thus making the platform unable to boot
properly.

Fixes: 26f09e9b ("mm/memblock: add memblock memory allocation apis")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/include/asm/dma.h

@@ -10,7 +10,7 @@
 #else
 #define MAX_DMA_ADDRESS	({ \
 	extern phys_addr_t arm_dma_zone_size; \
-	arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
+	arm_dma_zone_size && arm_dma_zone_size < (0x100000000ULL - PAGE_OFFSET) ? \
 		(PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
 #endif