drm/i915: Align dumb buffer stride to 4k to allow for gtt remapping

Align dumb buffer stride to 4k if the fb will be big enough to
require gtt remapping.

v2: Leave the stride alone for buffers that look to be for the cursor
v3: Make it not a hack (Daniel)

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190509122159.24376-7-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/i915_gem.c

@@ -52,6 +52,7 @@
 #include "i915_trace.h"
 #include "i915_vgpu.h"
 
+#include "intel_display.h"
 #include "intel_drv.h"
 #include "intel_frontbuffer.h"
 #include "intel_pm.h"
@@ -560,8 +561,31 @@ i915_gem_dumb_create(struct drm_file *file,
 		     struct drm_device *dev,
 		     struct drm_mode_create_dumb *args)
 {
+	int cpp = DIV_ROUND_UP(args->bpp, 8);
+	u32 format;
+
+	switch (cpp) {
+	case 1:
+		format = DRM_FORMAT_C8;
+		break;
+	case 2:
+		format = DRM_FORMAT_RGB565;
+		break;
+	case 4:
+		format = DRM_FORMAT_XRGB8888;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	/* have to work out size/pitch and return them */
-	args->pitch = ALIGN(args->width * DIV_ROUND_UP(args->bpp, 8), 64);
+	args->pitch = ALIGN(args->width * cpp, 64);
+
+	/* align stride to page size so that we can remap */
+	if (args->pitch > intel_plane_fb_max_stride(to_i915(dev), format,
+						    DRM_FORMAT_MOD_LINEAR))
+		args->pitch = ALIGN(args->pitch, 4096);
+
 	args->size = args->pitch * args->height;
 	return i915_gem_create(file, to_i915(dev),
 			       &args->size, &args->handle);

drivers/gpu/drm/i915/intel_display.c

@@ -2498,7 +2498,6 @@ bool is_ccs_modifier(u64 modifier)
 	       modifier == I915_FORMAT_MOD_Yf_TILED_CCS;
 }
 
-static
 u32 intel_plane_fb_max_stride(struct drm_i915_private *dev_priv,
 			      u32 pixel_format, u64 modifier)
 {

drivers/gpu/drm/i915/intel_display.h

@@ -436,6 +436,8 @@ void intel_link_compute_m_n(u16 bpp, int nlanes,
 			    bool constant_n);
 bool is_ccs_modifier(u64 modifier);
 void lpt_disable_clkout_dp(struct drm_i915_private *dev_priv);
+u32 intel_plane_fb_max_stride(struct drm_i915_private *dev_priv,
+			      u32 pixel_format, u64 modifier);
 bool intel_plane_can_remap(const struct intel_plane_state *plane_state);
 
 #endif