drm/i915/gtt: Introduce i915_page_dir_dma_addr

The legacy mode mm switch and the execlist context assignment
needs dma address for the page directories.

Introduce a function that encapsulates the scratch_pd dma
fallback if no pd is found.

v2: Rebase, s/ring/req
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -482,10 +482,8 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
 	int i, ret;
 
 	for (i = GEN8_LEGACY_PDPES - 1; i >= 0; i--) {
-		struct i915_page_directory *pd = ppgtt->pdp.page_directory[i];
-		dma_addr_t pd_daddr = pd ? pd->daddr : ppgtt->scratch_pd->daddr;
-		/* The page directory might be NULL, but we need to clear out
-		 * whatever the previous context might have used. */
+		const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);
+
 		ret = gen8_write_pdp(req, i, pd_daddr);
 		if (ret)
 			return ret;

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -470,6 +470,14 @@ static inline size_t gen8_pte_count(uint64_t address, uint64_t length)
 	return i915_pte_count(address, length, GEN8_PDE_SHIFT);
 }
 
+static inline dma_addr_t
+i915_page_dir_dma_addr(const struct i915_hw_ppgtt *ppgtt, const unsigned n)
+{
+	return test_bit(n, ppgtt->pdp.used_pdpes) ?
+		ppgtt->pdp.page_directory[n]->daddr :
+		ppgtt->scratch_pd->daddr;
+}
+
 int i915_gem_gtt_init(struct drm_device *dev);
 void i915_gem_init_global_gtt(struct drm_device *dev);
 void i915_global_gtt_cleanup(struct drm_device *dev);

drivers/gpu/drm/i915/intel_lrc.c

@@ -190,9 +190,7 @@
 #define GEN8_CTX_PRIVILEGE (1<<8)
 
 #define ASSIGN_CTX_PDP(ppgtt, reg_state, n) { \
-	const u64 _addr = test_bit(n, ppgtt->pdp.used_pdpes) ? \
-		ppgtt->pdp.page_directory[n]->daddr : \
-		ppgtt->scratch_pd->daddr; \
+	const u64 _addr = i915_page_dir_dma_addr((ppgtt), (n));	\
 	reg_state[CTX_PDP ## n ## _UDW+1] = upper_32_bits(_addr); \
 	reg_state[CTX_PDP ## n ## _LDW+1] = lower_32_bits(_addr); \
 }