[PATCH] drm/fb: don't call driver set_config if display isn't panned

[Jesse Barnes]

This is just a minor optimization to the fb panning code.  In debugging
some other issues, I noticed a lot of no-op calls to the set_config
routine with all the same parameters and tracked down the source to the
fb helper pan routine.

So add an additional check for actual panning relative to the current
crtc config to avoid unnecessary set_config calls.

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index f7c6854..4dd81f3 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -739,7 +739,8 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
 		modeset->x = var->xoffset;
 		modeset->y = var->yoffset;
 
-		if (modeset->num_connectors) {
+		if (((modeset->x != crtc->x) || (modeset->y != crtc->y)) &&
+		    modeset->num_connectors) {
 			ret = crtc->funcs->set_config(modeset);
 			if (!ret) {
 				info->var.xoffset = var->xoffset;
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