@@ -116,8 +116,14 @@ static void __init arch_reserve_crashkernel(void)
static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
{
- if (zone_limit == PHYS_ADDR_MAX)
- zone_limit = U32_MAX;
+ /**
+ * Information we get from firmware (e.g. DT dma-ranges) describe DMA
+ * bus constraints. Devices using DMA might have their own limitations.
+ * Some of them rely on DMA zone in low 32-bit memory. Keep low RAM
+ * DMA zone on platforms that have RAM there.
+ */
+ if (memblock_start_of_DRAM() < U32_MAX)
+ zone_limit = min(zone_limit, U32_MAX);
return min(zone_limit, memblock_end_of_DRAM() - 1) + 1;
}
Commit ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by zone_dma_limit") optimistically assumed that device-tree dma-ranges property describes the system DMA limits. That assumption ignores DMA limits of individual devices that are not encoded in device tree. Commit 833bd284a45 ("arm64: mm: fix DMA zone when dma-ranges is missing") fixed part of the problem for platforms that do not provide dma-ranges at all. However platforms like SM8550-HDK provide DMA bus limit, but have devices with stronger DMA limits. of_dma_get_max_cpu_address() does not take device limitations into account. These platforms implicitly rely on DMA zone in low 32-bit RAM area. Until we find a better way to figure out the optimal DMA zone range, restore the low RAM DMA zone we had before commit ba0fb44aed47. Fixes: ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by zone_dma_limit") Reported-by: Neil Armstrong <neil.armstrong@linaro.org> Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-HDK Closes: https://lore.kernel.org/r/1a0c7282-63e0-4add-8e38-3abe3e0a8e2f@linaro.org Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Suggested-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Baruch Siach <baruch@tkos.co.il> --- arch/arm64/mm/init.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)