drm/i915: Cleanup some of the CSB handling

I think this patch is a worthwhile cleanup even if it might look only marginally
useful. It gets more useful in upcoming patches and for handling of future GEN
platforms.

The only non-mechanical part of this is the removal of the extra & operation on
the ring->next_context_status_buffer. This is safe because right above this, we
already did a modulus operation.

Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452018609-10142-2-git-send-email-benjamin.widawsky@intel.com
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 0fc38bb..3b05bd1 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2092,13 +2092,13 @@
 		seq_printf(m, "\tStatus pointer: 0x%08X\n", status_pointer);
 
 		read_pointer = ring->next_context_status_buffer;
-		write_pointer = status_pointer & 0x07;
+		write_pointer = GEN8_CSB_WRITE_PTR(status_pointer);
 		if (read_pointer > write_pointer)
-			write_pointer += 6;
+			write_pointer += GEN8_CSB_ENTRIES;
 		seq_printf(m, "\tRead pointer: 0x%08X, write pointer 0x%08X\n",
 			   read_pointer, write_pointer);
 
-		for (i = 0; i < 6; i++) {
+		for (i = 0; i < GEN8_CSB_ENTRIES; i++) {
 			status = I915_READ(RING_CONTEXT_STATUS_BUF_LO(ring, i));
 			ctx_id = I915_READ(RING_CONTEXT_STATUS_BUF_HI(ring, i));