linux-kernel - [PATCH v4 2/3] drm/nouveau/fb/gf100: defer DMA mapping of scratch page to init() hook

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Date:   Mon, 26 Sep 2016 05:32:39 -0700
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     linux-kernel@...r.kernel.org, bskeggs@...hat.com, airlied@...ux.ie,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH v4 2/3] drm/nouveau/fb/gf100: defer DMA mapping of scratch page to init() hook

The 100c10 scratch page is mapped using dma_map_page() before the TTM
layer has had a chance to set the DMA mask. This means we are still
running with the default of 32 when this code executes, and this causes
problems for platforms with no memory below 4 GB (such as AMD Seattle)

So move the dma_map_page() to the .init hook, which executes after the
DMA mask has been set.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 drivers/gpu/drm/nouveau/nvkm/subdev/fb/gf100.c | 26 ++++++++++++++------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/fb/gf100.c b/drivers/gpu/drm/nouveau/nvkm/subdev/fb/gf100.c
index 76433cc66fff..5c8132873e60 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/fb/gf100.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/fb/gf100.c
@@ -93,7 +93,18 @@ gf100_fb_init(struct nvkm_fb *base)
 	struct gf100_fb *fb = gf100_fb(base);
 	struct nvkm_device *device = fb->base.subdev.device;
 
-	if (fb->r100c10_page)
+	if (!fb->r100c10) {
+		dma_addr_t addr = dma_map_page(device->dev, fb->r100c10_page, 0,
+					       PAGE_SIZE, DMA_BIDIRECTIONAL);
+		if (!dma_mapping_error(device->dev, addr)) {
+			fb->r100c10 = addr;
+		} else {
+			nvkm_warn(&fb->base.subdev,
+				 "dma_map_page() failed on 100c10 page\n");
+		}
+	}
+
+	if (fb->r100c10)
 		nvkm_wr32(device, 0x100c10, fb->r100c10 >> 8);
 }
 
@@ -103,12 +114,13 @@ gf100_fb_dtor(struct nvkm_fb *base)
 	struct gf100_fb *fb = gf100_fb(base);
 	struct nvkm_device *device = fb->base.subdev.device;
 
-	if (fb->r100c10_page) {
+	if (fb->r100c10) {
 		dma_unmap_page(device->dev, fb->r100c10, PAGE_SIZE,
 			       DMA_BIDIRECTIONAL);
-		__free_page(fb->r100c10_page);
 	}
 
+	__free_page(fb->r100c10_page);
+
 	return fb;
 }
 
@@ -124,11 +136,9 @@ gf100_fb_new_(const struct nvkm_fb_func *func, struct nvkm_device *device,
 	*pfb = &fb->base;
 
 	fb->r100c10_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
-	if (fb->r100c10_page) {
-		fb->r100c10 = dma_map_page(device->dev, fb->r100c10_page, 0,
-					   PAGE_SIZE, DMA_BIDIRECTIONAL);
-		if (dma_mapping_error(device->dev, fb->r100c10))
-			return -EFAULT;
+	if (!fb->r100c10_page) {
+		nvkm_error(&fb->base.subdev, "failed 100c10 page alloc\n");
+		return -ENOMEM;
 	}
 
 	return 0;
-- 
2.7.4