[PATCH 3/3] drm/mgag200: Map fbdev framebuffer while it's being displayed

[Thomas Zimmermann <tzimmermann@suse.de>]

The generic fbdev emulation will map and unmap the framebuffer's memory
if required. As consoles are most often updated while being on screen,
we map the fbdev buffer while it's being displayed. This avoids frequent
map/unmap operations in the fbdev code. The original fbdev code in mgag200
used the same trick to improve performance.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 90f479ae51af ("drm/mgag200: Replace struct mga_fbdev with generic framebuffer emulation")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: Armijn Hemel <armijn@tjaldur.nl>
Cc: Rong Chen <rong.a.chen@intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
---
 drivers/gpu/drm/mgag200/mgag200_mode.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index 822f2a13748f..a6391144feb5 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -860,13 +860,20 @@ static int mga_crtc_do_set_base(struct drm_crtc *crtc,
 				struct drm_framebuffer *fb,
 				int x, int y, int atomic)
 {
+	struct drm_fb_helper *fb_helper = crtc->dev->fb_helper;
 	struct drm_gem_vram_object *gbo;
 	int ret;
 	s64 gpu_addr;
+	void *base;
 
 	if (!atomic && fb) {
 		gbo = drm_gem_vram_of_gem(fb->obj[0]);
 		drm_gem_vram_unpin(gbo);
+
+		// Unmap fbdev FB if it's not being displayed
+		// any longer.
+		if (fb == fb_helper->buffer->fb)
+			drm_gem_vram_kunmap(gbo);
 	}
 
 	gbo = drm_gem_vram_of_gem(crtc->primary->fb->obj[0]);
@@ -882,6 +889,15 @@ static int mga_crtc_do_set_base(struct drm_crtc *crtc,
 
 	mga_set_start_address(crtc, (u32)gpu_addr);
 
+	// Map fbdev FB while it's being displayed. This
+	// avoids frequent mapping and unmapping withing the
+	// fbdev code.
+	if (crtc->primary->fb == fb_helper->buffer->fb) {
+		base = drm_gem_vram_kmap(gbo, true, NULL);
+		if (IS_ERR(base))
+			DRM_ERROR("failed to kmap fbcon\n");
+	}
+
 	return 0;
 
 err_drm_gem_vram_unpin:
@@ -1403,9 +1419,14 @@ static void mga_crtc_disable(struct drm_crtc *crtc)
 	DRM_DEBUG_KMS("\n");
 	mga_crtc_dpms(crtc, DRM_MODE_DPMS_OFF);
 	if (crtc->primary->fb) {
+		struct drm_fb_helper *fb_helper = crtc->dev->fb_helper;
 		struct drm_framebuffer *fb = crtc->primary->fb;
 		struct drm_gem_vram_object *gbo =
 			drm_gem_vram_of_gem(fb->obj[0]);
+
+		// Unmap if it's the fbdev FB.
+		if (fb == fb_helper->buffer->fb)
+			drm_gem_vram_kunmap(gbo);
 		drm_gem_vram_unpin(gbo);
 	}
 	crtc->primary->fb = NULL;
-- 
2.22.0

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