Re: [PATCH] drm/fbdev: Clamp fbdev surface size if too large

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Hi

Am 04.10.21 um 10:23 schrieb Ville Syrjälä:
On Mon, Oct 04, 2021 at 10:15:06AM +0200, Thomas Zimmermann wrote:
Clamp the fbdev surface size of the available maximum 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.

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
Reported-by: Amanoel Dawod <kernel@xxxxxxxxxxxxxxxx>
Reported-by: Zoltán Kővágó <dirty.ice.hu@xxxxxxxxx>
Reported-by: Michael Stapelberg <michael+lkml@xxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Maxime Ripard <maxime@xxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v5.14+
---
  drivers/gpu/drm/drm_fb_helper.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 6860223f0068..364f11900b37 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1508,6 +1508,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
  {
  	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;
@@ -1665,6 +1666,11 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
  	/* Handle our overallocation */
  	sizes.surface_height *= drm_fbdev_overalloc;
  	sizes.surface_height /= 100;
+	if (sizes.surface_height > config->max_height) {
+		drm_warn(dev, "Fbdev over-allocation too large; clamping height to %d\n",
+			 config->max_height);

drm_warn() seems a bit excessive. drm_info()?

Or could just have no printk and use a simple min() perhaps.

The framebuffer code uses debug_kms for this kind of message. I guess, I'll go with that.

Best regards
Thamas


+		sizes.surface_height = config->max_height;
+	}

  	/* push down into drivers */
  	ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);
--
2.33.0


--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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