iommu/omap-iovmm: support non page-aligned buffers in iommu_vmap

omap_iovmm requires page-aligned buffers, and that sometimes causes
omap3isp failures (i.e. whenever the buffer passed from userspace is not
page-aligned).

Remove this limitation by rounding the address of the first page entry
down, and adding the offset back to the device address.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
[ohad@wizery.com: rebased, but tested only with aligned buffers]
[ohad@wizery.com: slightly edited the commit log]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

drivers/iommu/omap-iovmm.c

@@ -27,6 +27,15 @@
 
 static struct kmem_cache *iovm_area_cachep;
 
+/* return the offset of the first scatterlist entry in a sg table */
+static unsigned int sgtable_offset(const struct sg_table *sgt)
+{
+	if (!sgt || !sgt->nents)
+		return 0;
+
+	return sgt->sgl->offset;
+}
+
 /* return total bytes of sg buffers */
 static size_t sgtable_len(const struct sg_table *sgt)
 {
@@ -39,11 +48,17 @@ static size_t sgtable_len(const struct sg_table *sgt)
 	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
 		size_t bytes;
 
-		bytes = sg->length;
+		bytes = sg->length + sg->offset;
 
 		if (!iopgsz_ok(bytes)) {
-			pr_err("%s: sg[%d] not iommu pagesize(%x)\n",
-			       __func__, i, bytes);
+			pr_err("%s: sg[%d] not iommu pagesize(%u %u)\n",
+			       __func__, i, bytes, sg->offset);
+			return 0;
+		}
+
+		if (i && sg->offset) {
+			pr_err("%s: sg[%d] offset not allowed in internal "
+					"entries\n", __func__, i);
 			return 0;
 		}
 
@@ -164,8 +179,8 @@ static void *vmap_sg(const struct sg_table *sgt)
 		u32 pa;
 		int err;
 
-		pa = sg_phys(sg);
-		bytes = sg->length;
+		pa = sg_phys(sg) - sg->offset;
+		bytes = sg->length + sg->offset;
 
 		BUG_ON(bytes != PAGE_SIZE);
 
@@ -405,8 +420,8 @@ static int map_iovm_area(struct iommu_domain *domain, struct iovm_struct *new,
 		u32 pa;
 		size_t bytes;
 
-		pa = sg_phys(sg);
-		bytes = sg->length;
+		pa = sg_phys(sg) - sg->offset;
+		bytes = sg->length + sg->offset;
 
 		flags &= ~IOVMF_PGSZ_MASK;
 
@@ -432,7 +447,7 @@ err_out:
 	for_each_sg(sgt->sgl, sg, i, j) {
 		size_t bytes;
 
-		bytes = sg->length;
+		bytes = sg->length + sg->offset;
 		order = get_order(bytes);
 
 		/* ignore failures.. we're already handling one */
@@ -461,7 +476,7 @@ static void unmap_iovm_area(struct iommu_domain *domain, struct omap_iommu *obj,
 		size_t bytes;
 		int order;
 
-		bytes = sg->length;
+		bytes = sg->length + sg->offset;
 		order = get_order(bytes);
 
 		err = iommu_unmap(domain, start, order);
@@ -600,7 +615,7 @@ u32 omap_iommu_vmap(struct iommu_domain *domain, struct omap_iommu *obj, u32 da,
 	if (IS_ERR_VALUE(da))
 		vunmap_sg(va);
 
-	return da;
+	return da + sgtable_offset(sgt);
 }
 EXPORT_SYMBOL_GPL(omap_iommu_vmap);
 
@@ -620,6 +635,7 @@ omap_iommu_vunmap(struct iommu_domain *domain, struct omap_iommu *obj, u32 da)
 	 * 'sgt' is allocated before 'omap_iommu_vmalloc()' is called.
 	 * Just returns 'sgt' to the caller to free
 	 */
+	da &= PAGE_MASK;
 	sgt = unmap_vm_area(domain, obj, da, vunmap_sg,
 					IOVMF_DISCONT | IOVMF_MMIO);
 	if (!sgt)