[PATCH v3 2/3] dma-mapping: replace zone_dma_bits by zone_dma_limit

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From: Catalin Marinas <catalin.marinas@xxxxxxx>

Hardware DMA limit might not be power of 2. When RAM range starts above
0, say 4GB, DMA limit of 30 bits should end at 5GB. A single high bit
can not encode this limit.

Use direct phys_addr_t limit address for DMA zone limit.

Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
---
 arch/arm64/mm/init.c       | 34 +++++++++++++---------------------
 arch/powerpc/mm/mem.c      |  9 ++++-----
 arch/s390/mm/init.c        |  2 +-
 include/linux/dma-direct.h |  2 +-
 kernel/dma/direct.c        |  4 ++--
 kernel/dma/pool.c          |  2 +-
 kernel/dma/swiotlb.c       |  4 ++--
 7 files changed, 24 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9b5ab6818f7f..870fd967c610 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -114,36 +114,28 @@ static void __init arch_reserve_crashkernel(void)
 				    low_size, high);
 }
 
-/*
- * Return the maximum physical address for a zone accessible by the given bits
- * limit. If DRAM starts above 32-bit, expand the zone to the maximum
- * available memory, otherwise cap it at 32-bit.
- */
-static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
+static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
 {
-	phys_addr_t zone_mask = DMA_BIT_MASK(zone_bits);
-	phys_addr_t phys_start = memblock_start_of_DRAM();
-
-	if (phys_start > U32_MAX)
-		zone_mask = PHYS_ADDR_MAX;
-	else if (phys_start > zone_mask)
-		zone_mask = U32_MAX;
+	/* We have RAM in low 32-bit area, keep DMA zone there */
+	if (memblock_start_of_DRAM() < U32_MAX)
+		zone_limit = min(U32_MAX, zone_limit);
 
-	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
+	return min(zone_limit, memblock_end_of_DRAM() - 1) + 1;
 }
 
 static void __init zone_sizes_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
-	unsigned int __maybe_unused acpi_zone_dma_bits;
-	unsigned int __maybe_unused dt_zone_dma_bits;
-	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
+	phys_addr_t __maybe_unused acpi_zone_dma_limit;
+	phys_addr_t __maybe_unused dt_zone_dma_limit;
+	phys_addr_t __maybe_unused dma32_phys_limit =
+		max_zone_phys(DMA_BIT_MASK(32));
 
 #ifdef CONFIG_ZONE_DMA
-	acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
-	dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
-	zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
-	arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
+	acpi_zone_dma_limit = acpi_iort_dma_get_max_cpu_address();
+	dt_zone_dma_limit = of_dma_get_max_cpu_address(NULL);
+	zone_dma_limit = min(dt_zone_dma_limit, acpi_zone_dma_limit);
+	arm64_dma_phys_limit = max_zone_phys(zone_dma_limit);
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
 #endif
 #ifdef CONFIG_ZONE_DMA32
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index d325217ab201..342c006cc1b8 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -216,7 +216,7 @@ static int __init mark_nonram_nosave(void)
  * everything else. GFP_DMA32 page allocations automatically fall back to
  * ZONE_DMA.
  *
- * By using 31-bit unconditionally, we can exploit zone_dma_bits to inform the
+ * By using 31-bit unconditionally, we can exploit zone_dma_limit to inform the
  * generic DMA mapping code.  32-bit only devices (if not handled by an IOMMU
  * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
  * ZONE_DMA.
@@ -252,13 +252,12 @@ void __init paging_init(void)
 	 * powerbooks.
 	 */
 	if (IS_ENABLED(CONFIG_PPC32))
-		zone_dma_bits = 30;
+		zone_dma_limit = DMA_BIT_MASK(30);
 	else
-		zone_dma_bits = 31;
+		zone_dma_limit = DMA_BIT_MASK(31);
 
 #ifdef CONFIG_ZONE_DMA
-	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
-				      1UL << (zone_dma_bits - PAGE_SHIFT));
+	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn, zone_dma_limit >> PAGE_SHIFT);
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
 #ifdef CONFIG_HIGHMEM
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index ddcd39ef4346..91fc2b91adfc 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -97,7 +97,7 @@ void __init paging_init(void)
 
 	vmem_map_init();
 	sparse_init();
-	zone_dma_bits = 31;
+	zone_dma_limit = DMA_BIT_MASK(31);
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index edbe13d00776..98b7d8015043 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -12,7 +12,7 @@
 #include <linux/mem_encrypt.h>
 #include <linux/swiotlb.h>
 
-extern unsigned int zone_dma_bits;
+extern phys_addr_t zone_dma_limit;
 
 /*
  * Record the mapping of CPU physical to DMA addresses for a given region.
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 3b4be4ca3b08..3dbc0b89d6fb 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -20,7 +20,7 @@
  * it for entirely different regions. In that case the arch code needs to
  * override the variable below for dma-direct to work properly.
  */
-unsigned int zone_dma_bits __ro_after_init = 24;
+phys_addr_t zone_dma_limit __ro_after_init = DMA_BIT_MASK(24);
 
 static inline dma_addr_t phys_to_dma_direct(struct device *dev,
 		phys_addr_t phys)
@@ -580,7 +580,7 @@ int dma_direct_supported(struct device *dev, u64 mask)
 	 * part of the check.
 	 */
 	if (IS_ENABLED(CONFIG_ZONE_DMA))
-		min_mask = min_t(u64, min_mask, DMA_BIT_MASK(zone_dma_bits));
+		min_mask = min_t(u64, min_mask, zone_dma_limit);
 	return mask >= phys_to_dma_unencrypted(dev, min_mask);
 }
 
diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index d10613eb0f63..410a7b40e496 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -70,7 +70,7 @@ static bool cma_in_zone(gfp_t gfp)
 	/* CMA can't cross zone boundaries, see cma_activate_area() */
 	end = cma_get_base(cma) + size - 1;
 	if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA))
-		return end <= DMA_BIT_MASK(zone_dma_bits);
+		return end <= zone_dma_limit;
 	if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32))
 		return end <= DMA_BIT_MASK(32);
 	return true;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index df68d29740a0..dfd83e5ee0b3 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -450,7 +450,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
 	if (!remap)
 		io_tlb_default_mem.can_grow = true;
 	if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp_mask & __GFP_DMA))
-		io_tlb_default_mem.phys_limit = DMA_BIT_MASK(zone_dma_bits);
+		io_tlb_default_mem.phys_limit = zone_dma_limit;
 	else if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp_mask & __GFP_DMA32))
 		io_tlb_default_mem.phys_limit = DMA_BIT_MASK(32);
 	else
@@ -629,7 +629,7 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes,
 	}
 
 	gfp &= ~GFP_ZONEMASK;
-	if (phys_limit <= DMA_BIT_MASK(zone_dma_bits))
+	if (phys_limit <= zone_dma_limit)
 		gfp |= __GFP_DMA;
 	else if (phys_limit <= DMA_BIT_MASK(32))
 		gfp |= __GFP_DMA32;
-- 
2.43.0





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