[PATCH] arm64: mm: fix DMA zone when dma-ranges is missing

[Baruch Siach]

Some platforms, like Rockchip RK3568 based Odroid M1, do not provide DMA
limits information in device-tree dma-ranges property. Still some device
drivers set DMA limit that relies on DMA zone at low 4GB memory area.
Until commit ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by
zone_dma_limit"), zone_sizes_init() restricted DMA zone to low 32-bit
when there is RAM there.

Restore DMA zone 32-bit limit for platforms that have RAM in this area.

Fixes: ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by zone_dma_limit")
Reported-by: Marek Szyprowski <m.szyprowski at samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
This should go via the dma-mapping tree that contains the fixed commit.
---
 arch/arm64/mm/init.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index bfb10969cbf0..7fcd0aaa9bb6 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -116,6 +116,9 @@ static void __init arch_reserve_crashkernel(void)
 
 static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
 {
+	if (memblock_start_of_DRAM() < U32_MAX)
+		zone_limit = min(zone_limit, U32_MAX);
+
 	return min(zone_limit, memblock_end_of_DRAM() - 1) + 1;
 }
 
-- 
2.45.2