[PATCH 5.14 025/151] drm/fbdev: Clamp fbdev surface size if too large

[Greg Kroah-Hartman]

From: Thomas Zimmermann <tzimmermann at suse.de>

commit b693e42921e0220c0d564c55c6cdc680b0f85390 upstream.

Clamp the fbdev surface size of the available maximumi height to avoid
failing to init console emulation. An example error is shown below.

  bad framebuffer height 2304, should be >= 768 && <= 768
  [drm] Initialized simpledrm 1.0.0 20200625 for simple-framebuffer.0 on minor 0
  simple-framebuffer simple-framebuffer.0: [drm] *ERROR* fbdev: Failed to setup generic emulation (ret=-22)

This is especially a problem with drivers that have very small screen
sizes and cannot over-allocate at all.

v2:
	* reduce warning level (Ville)

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
Reported-by: Amanoel Dawod <kernel at amanoeldawod.com>
Reported-by: Zoltán Kővágó <dirty.ice.hu at gmail.com>
Reported-by: Michael Stapelberg <michael+lkml at stapelberg.ch>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Maxime Ripard <maxime at cerno.tech>
Cc: dri-devel at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v5.14+
Link: https://patchwork.freedesktop.org/patch/msgid/20211005070355.7680-1-tzimmermann@suse.de
Signed-off-by: Dave Airlie <airlied at redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/gpu/drm/drm_fb_helper.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1506,6 +1506,7 @@ static int drm_fb_helper_single_fb_probe
 {
 	struct drm_client_dev *client = &fb_helper->client;
 	struct drm_device *dev = fb_helper->dev;
+	struct drm_mode_config *config = &dev->mode_config;
 	int ret = 0;
 	int crtc_count = 0;
 	struct drm_connector_list_iter conn_iter;
@@ -1663,6 +1664,11 @@ static int drm_fb_helper_single_fb_probe
 	/* Handle our overallocation */
 	sizes.surface_height *= drm_fbdev_overalloc;
 	sizes.surface_height /= 100;
+	if (sizes.surface_height > config->max_height) {
+		drm_dbg_kms(dev, "Fbdev over-allocation too large; clamping height to %d\n",
+			    config->max_height);
+		sizes.surface_height = config->max_height;
+	}
 
 	/* push down into drivers */
 	ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);