Subject: [PATCH v5 07/14] alpha: Convert mapping routine to rely on physical address

From: Leon Romanovsky <[email-masked]>
Date: Wed, 15 Oct 2025 12:12:53 +0300

From: Leon Romanovsky <[email-masked]>

Alpha doesn't need struct *page and can perform mapping based on
physical addresses. So convert it to implement new .map_phys callback.

As part of this change, remove useless BUG_ON() as DMA mapping layer
ensures that right direction is provided.

Tested-by: Magnus Lindholm <[email-masked]>
Reviewed-by: Jason Gunthorpe <[email-masked]>
Signed-off-by: Leon Romanovsky <[email-masked]>
---
 arch/alpha/kernel/pci_iommu.c | 48 +++++++++++++++++++------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index dc91de50f906..955b6ca61627 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -224,28 +224,26 @@ static int pci_dac_dma_supported(struct pci_dev *dev, u64 mask)
    until either pci_unmap_single or pci_dma_sync_single is performed.  */
 
 static dma_addr_t
-pci_map_single_1(struct pci_dev *pdev, void *cpu_addr, size_t size,
+pci_map_single_1(struct pci_dev *pdev, phys_addr_t paddr, size_t size,
 		 int dac_allowed)
 {
 	struct pci_controller *hose = pdev ? pdev->sysdata : pci_isa_hose;
 	dma_addr_t max_dma = pdev ? pdev->dma_mask : ISA_DMA_MASK;
+	unsigned long offset = offset_in_page(paddr);
 	struct pci_iommu_arena *arena;
 	long npages, dma_ofs, i;
-	unsigned long paddr;
 	dma_addr_t ret;
 	unsigned int align = 0;
 	struct device *dev = pdev ? &pdev->dev : NULL;
 
-	paddr = __pa(cpu_addr);
-
 #if !DEBUG_NODIRECT
 	/* First check to see if we can use the direct map window.  */
 	if (paddr + size + __direct_map_base - 1 <= max_dma
 	    && paddr + size <= __direct_map_size) {
 		ret = paddr + __direct_map_base;
 
-		DBGA2("pci_map_single: [%p,%zx] -> direct %llx from %ps\n",
-		      cpu_addr, size, ret, __builtin_return_address(0));
+		DBGA2("pci_map_single: [%pa,%zx] -> direct %llx from %ps\n",
+		      &paddr, size, ret, __builtin_return_address(0));
 
 		return ret;
 	}
@@ -255,8 +253,8 @@ pci_map_single_1(struct pci_dev *pdev, void *cpu_addr, size_t size,
 	if (dac_allowed) {
 		ret = paddr + alpha_mv.pci_dac_offset;
 
-		DBGA2("pci_map_single: [%p,%zx] -> DAC %llx from %ps\n",
-		      cpu_addr, size, ret, __builtin_return_address(0));
+		DBGA2("pci_map_single: [%pa,%zx] -> DAC %llx from %ps\n",
+		      &paddr, size, ret, __builtin_return_address(0));
 
 		return ret;
 	}
@@ -290,10 +288,10 @@ pci_map_single_1(struct pci_dev *pdev, void *cpu_addr, size_t size,
 		arena->ptes[i + dma_ofs] = mk_iommu_pte(paddr);
 
 	ret = arena->dma_base + dma_ofs * PAGE_SIZE;
-	ret += (unsigned long)cpu_addr & ~PAGE_MASK;
+	ret += offset;
 
-	DBGA2("pci_map_single: [%p,%zx] np %ld -> sg %llx from %ps\n",
-	      cpu_addr, size, npages, ret, __builtin_return_address(0));
+	DBGA2("pci_map_single: [%pa,%zx] np %ld -> sg %llx from %ps\n",
+	      &paddr, size, npages, ret, __builtin_return_address(0));
 
 	return ret;
 }
@@ -322,19 +320,18 @@ static struct pci_dev *alpha_gendev_to_pci(struct device *dev)
 	return NULL;
 }
 
-static dma_addr_t alpha_pci_map_page(struct device *dev, struct page *page,
-				     unsigned long offset, size_t size,
-				     enum dma_data_direction dir,
+static dma_addr_t alpha_pci_map_phys(struct device *dev, phys_addr_t phys,
+				     size_t size, enum dma_data_direction dir,
 				     unsigned long attrs)
 {
 	struct pci_dev *pdev = alpha_gendev_to_pci(dev);
 	int dac_allowed;
 
-	BUG_ON(dir == DMA_NONE);
+	if (unlikely(attrs & DMA_ATTR_MMIO))
+		return DMA_MAPPING_ERROR;
 
-	dac_allowed = pdev ? pci_dac_dma_supported(pdev, pdev->dma_mask) : 0; 
-	return pci_map_single_1(pdev, (char *)page_address(page) + offset, 
-				size, dac_allowed);
+	dac_allowed = pdev ? pci_dac_dma_supported(pdev, pdev->dma_mask) : 0;
+	return pci_map_single_1(pdev, phys, size, dac_allowed);
 }
 
 /* Unmap a single streaming mode DMA translation.  The DMA_ADDR and
@@ -343,7 +340,7 @@ static dma_addr_t alpha_pci_map_page(struct device *dev, struct page *page,
    the cpu to the buffer are guaranteed to see whatever the device
    wrote there.  */
 
-static void alpha_pci_unmap_page(struct device *dev, dma_addr_t dma_addr,
+static void alpha_pci_unmap_phys(struct device *dev, dma_addr_t dma_addr,
 				 size_t size, enum dma_data_direction dir,
 				 unsigned long attrs)
 {
@@ -353,8 +350,6 @@ static void alpha_pci_unmap_page(struct device *dev, dma_addr_t dma_addr,
 	struct pci_iommu_arena *arena;
 	long dma_ofs, npages;
 
-	BUG_ON(dir == DMA_NONE);
-
 	if (dma_addr >= __direct_map_base
 	    && dma_addr < __direct_map_base + __direct_map_size) {
 		/* Nothing to do.  */
@@ -429,7 +424,7 @@ static void *alpha_pci_alloc_coherent(struct device *dev, size_t size,
 	}
 	memset(cpu_addr, 0, size);
 
-	*dma_addrp = pci_map_single_1(pdev, cpu_addr, size, 0);
+	*dma_addrp = pci_map_single_1(pdev, virt_to_phys(cpu_addr), size, 0);
 	if (*dma_addrp == DMA_MAPPING_ERROR) {
 		free_pages((unsigned long)cpu_addr, order);
 		if (alpha_mv.mv_pci_tbi || (gfp & GFP_DMA))
@@ -643,9 +638,8 @@ static int alpha_pci_map_sg(struct device *dev, struct scatterlist *sg,
 	/* Fast path single entry scatterlists.  */
 	if (nents == 1) {
 		sg->dma_length = sg->length;
-		sg->dma_address
-		  = pci_map_single_1(pdev, SG_ENT_VIRT_ADDRESS(sg),
-				     sg->length, dac_allowed);
+		sg->dma_address = pci_map_single_1(pdev, sg_phys(sg),
+						   sg->length, dac_allowed);
 		if (sg->dma_address == DMA_MAPPING_ERROR)
 			return -EIO;
 		return 1;
@@ -917,8 +911,8 @@ iommu_unbind(struct pci_iommu_arena *arena, long pg_start, long pg_count)
 const struct dma_map_ops alpha_pci_ops = {
 	.alloc			= alpha_pci_alloc_coherent,
 	.free			= alpha_pci_free_coherent,
-	.map_page		= alpha_pci_map_page,
-	.unmap_page		= alpha_pci_unmap_page,
+	.map_phys		= alpha_pci_map_phys,
+	.unmap_phys		= alpha_pci_unmap_phys,
 	.map_sg			= alpha_pci_map_sg,
 	.unmap_sg		= alpha_pci_unmap_sg,
 	.dma_supported		= alpha_pci_supported,

-- 
2.51.0