drm/i915: s/for_each_sgt_dma/for_each_sgt_daddr/

The sg_table for our backing store might contain addresses from
stolen-memory or in the future local-memory, at which point this is no
longer a dma-iterator. As a consequence we should now break on NULL
iter.sgp, instead of dmap == 0 which is considered an invalid dma
address.

As a bonus, gcc much prefers this construct,

Function old new delta
gen8_ggtt_insert_entries 211 192 -19
gen6_ggtt_insert_entries 292 262 -30
i915_error_object_create 996 954 -42

Signed-off-by: Matthew Auld <[e-mail]>
Cc: Chris Wilson <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>
Signed-off-by: Chris Wilson <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/i915_gem_gtt.c

···
 
 	gtt_entries = (gen8_pte_t __iomem *)ggtt->gsm;
 	gtt_entries += vma->node.start / I915_GTT_PAGE_SIZE;
-	for_each_sgt_dma(addr, sgt_iter, vma->pages)
+	for_each_sgt_daddr(addr, sgt_iter, vma->pages)
 		gen8_set_pte(gtt_entries++, pte_encode | addr);
 
 	/*
···
 	unsigned int i = vma->node.start / I915_GTT_PAGE_SIZE;
 	struct sgt_iter iter;
 	dma_addr_t addr;
-	for_each_sgt_dma(addr, iter, vma->pages)
+	for_each_sgt_daddr(addr, iter, vma->pages)
 		iowrite32(vm->pte_encode(addr, level, flags), &entries[i++]);
 
 	/*

drivers/gpu/drm/i915/i915_gem_gtt.h

···
 #define GEN8_PDE_IPS_64K BIT(11)
 #define GEN8_PDE_PS_2M   BIT(7)
 
-#define for_each_sgt_dma(__dmap, __iter, __sgt) \
-	__for_each_sgt_dma(__dmap, __iter, __sgt, I915_GTT_PAGE_SIZE)
+#define for_each_sgt_daddr(__dp, __iter, __sgt) \
+	__for_each_sgt_daddr(__dp, __iter, __sgt, I915_GTT_PAGE_SIZE)
 
 struct intel_remapped_plane_info {
 	/* in gtt pages */

drivers/gpu/drm/i915/i915_gpu_error.c

···
 	dst->unused = 0;
 
 	ret = -EINVAL;
-	for_each_sgt_dma(dma, iter, vma->pages) {
+	for_each_sgt_daddr(dma, iter, vma->pages) {
 		void __iomem *s;
 
 		ggtt->vm.insert_page(&ggtt->vm, dma, slot, I915_CACHE_NONE, 0);

drivers/gpu/drm/i915/i915_scatterlist.h

···
 }
 
 /**
- * __for_each_sgt_dma - iterate over the DMA addresses of the given sg_table
- * @__dmap:	DMA address (output)
+ * __for_each_sgt_daddr - iterate over the device addresses of the given sg_table
+ * @__dp:	Device address (output)
  * @__iter:	'struct sgt_iter' (iterator state, internal)
  * @__sgt:	sg_table to iterate over (input)
  * @__step:	step size
  */
-#define __for_each_sgt_dma(__dmap, __iter, __sgt, __step)		\
+#define __for_each_sgt_daddr(__dp, __iter, __sgt, __step)		\
 	for ((__iter) = __sgt_iter((__sgt)->sgl, true);			\
-	     ((__dmap) = (__iter).dma + (__iter).curr);			\
+	     ((__dp) = (__iter).dma + (__iter).curr), (__iter).sgp;	\
 	     (((__iter).curr += (__step)) >= (__iter).max) ?		\
 	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0 : 0)
 

drivers/gpu/drm/i915/selftests/i915_vma.c

···
 	struct sgt_iter sgt;
 	dma_addr_t dma;
 
-	for_each_sgt_dma(dma, sgt, vma->pages) {
+	for_each_sgt_daddr(dma, sgt, vma->pages) {
 		dma_addr_t src;
 
 		if (!size) {