[Nouveau] [PATCH] drm/nouveau/kms: Implement KDB debug hooks for nouveau KMS.

[Chris Ball]

Hi Francisco,

   > There is a problem with this on pre-nv20 cards. Fbcon
   > acceleration won't work properly with IRQs disabled because you
   > miss the context switching interrupts: You'll get a locked up
   > fbcon if you hit sysrq-g when there's some process using the GPU.
   > 
   > I'd suggest disabling acceleration while in debug mode
   > (e.g. using nouveau_fbcon_save_disable_accel()). That aside the
   > patch looks good to me.

Thanks very much for this.  Here's a (only compile-tested) patch for
this, on top of jwessel's current kgdb-next branch.  Jason, would you
mind testing on pre-nv20 and applying?

Thanks,

- Chris.


From: Chris Ball <cjb at laptop.org>
Subject: [PATCH] drm/nouveau/kms: Avoid a hang entering KDB with VT accel on.

Francisco Jerez advises that pre-nv20 cards would hang if we entered
kdb with accel on and IRQs disabled, so we now disable accel before
entering kdb and re-enable it on the way back out.

Signed-off-by: Chris Ball <cjb at laptop.org>
Cc: Francisco Jerez <currojerez at riseup.net>
Cc: Jason Wessel <jason.wessel at windriver.com>
---
 drivers/gpu/drm/nouveau/nv04_crtc.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nv04_crtc.c b/drivers/gpu/drm/nouveau/nv04_crtc.c
index fb669dd..427f90e 100644
--- a/drivers/gpu/drm/nouveau/nv04_crtc.c
+++ b/drivers/gpu/drm/nouveau/nv04_crtc.c
@@ -31,10 +31,11 @@
 #include "nouveau_connector.h"
 #include "nouveau_crtc.h"
 #include "nouveau_fb.h"
 #include "nouveau_hw.h"
 #include "nvreg.h"
+#include "nouveau_fbcon.h"
 
 static int
 nv04_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
 			struct drm_framebuffer *old_fb);
 
@@ -858,10 +859,18 @@ nv04_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
 static int
 nv04_crtc_mode_set_base_atomic(struct drm_crtc *crtc,
 			       struct drm_framebuffer *fb,
 			       int x, int y, int enter)
 {
+	struct drm_nouveau_private *dev_priv = crtc->dev->dev_private;
+	struct drm_device *dev = dev_priv->dev;
+
+	if (enter)
+		nouveau_fbcon_save_disable_accel(dev);
+	else
+		nouveau_fbcon_restore_accel(dev);
+
 	return nv04_crtc_do_mode_set_base(crtc, fb, x, y, true);
 }
 
 static void nv04_cursor_upload(struct drm_device *dev, struct nouveau_bo *src,
 			       struct nouveau_bo *dst)
-- 
1.6.2.5