From 50d44d1152128df2932b15f063d0076a6ab00a8b Mon Sep 17 00:00:00 2001
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: Fri, 27 Mar 2020 17:21:26 +0100
Subject: drm/prime: fix extracting of the DMA addresses from a scatterlist
Git-commit: c0f83d164fb8f3a2b7bc379a6c1e27d1123a9eab
Patch-mainline: v5.7-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322

Scatterlist elements contains both pages and DMA addresses, but one
should not assume 1:1 relation between them. The sg->length is the size
of the physical memory chunk described by the sg->page, while
sg_dma_len(sg) is the size of the DMA (IO virtual) chunk described by
the sg_dma_address(sg).

The proper way of extracting both: pages and DMA addresses of the whole
buffer described by a scatterlist it to iterate independently over the
sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.

Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200327162126.29705-1-m.szyprowski@samsung.com
Cc: stable@vger.kernel.org
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/drm_prime.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1de2cde2277c..282774e469ac 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -962,27 +962,40 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
 	unsigned count;
 	struct scatterlist *sg;
 	struct page *page;
-	u32 len, index;
+	u32 page_len, page_index;
 	dma_addr_t addr;
+	u32 dma_len, dma_index;
 
-	index = 0;
+	/*
+	 * Scatterlist elements contains both pages and DMA addresses, but
+	 * one shoud not assume 1:1 relation between them. The sg->length is
+	 * the size of the physical memory chunk described by the sg->page,
+	 * while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk
+	 * described by the sg_dma_address(sg).
+	 */
+	page_index = 0;
+	dma_index = 0;
 	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
-		len = sg_dma_len(sg);
+		page_len = sg->length;
 		page = sg_page(sg);
+		dma_len = sg_dma_len(sg);
 		addr = sg_dma_address(sg);
 
-		while (len > 0) {
-			if (WARN_ON(index >= max_entries))
+		while (pages && page_len > 0) {
+			if (WARN_ON(page_index >= max_entries))
 				return -1;
-			if (pages)
-				pages[index] = page;
-			if (addrs)
-				addrs[index] = addr;
-
+			pages[page_index] = page;
 			page++;
+			page_len -= PAGE_SIZE;
+			page_index++;
+		}
+		while (addrs && dma_len > 0) {
+			if (WARN_ON(dma_index >= max_entries))
+				return -1;
+			addrs[dma_index] = addr;
 			addr += PAGE_SIZE;
-			len -= PAGE_SIZE;
-			index++;
+			dma_len -= PAGE_SIZE;
+			dma_index++;
 		}
 	}
 	return 0;
-- 
2.28.0