linux-kernel - [ 072/187] drm/nouveau/fbcon: using nv_two

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Message-Id: <20120712191529.079783605@linuxfoundation.org>
Date:	Thu, 12 Jul 2012 15:33:48 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ben Skeggs <bskeggs@...hat.com>,
	Dave Airlie <airlied@...hat.com>
Subject: [ 072/187] drm/nouveau/fbcon: using nv_two_heads is not a good idea

From: Greg KH <gregkh@...uxfoundation.org>

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Skeggs <bskeggs@...hat.com>

commit 9bd0c15fcfb42f6245447c53347d65ad9e72080b upstream.

nv_two_heads() was never meant to be used outside of pre-nv50 code.  The
code checks for >= NV_10 for 2 CRTCs, then downgrades a few specific
chipsets to 1 CRTC based on (pci_device & 0x0ff0).

The breakage example seen is on GTX 560Ti, with a pciid of 0x1200, which
gets detected as an NV20 (0x020x) with 1 CRTC by nv_two_heads(), causing
memory corruption because there's actually 2 CRTCs..

This switches fbcon to use the CRTC count directly from the mode_config
structure, which will also fix the same issue on Kepler boards which have
4 CRTCs.

Signed-off-by: Ben Skeggs <bskeggs@...hat.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/nouveau/nouveau_fbcon.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -497,7 +497,7 @@ int nouveau_fbcon_init(struct drm_device
 	nfbdev->helper.funcs = &nouveau_fbcon_helper_funcs;
 
 	ret = drm_fb_helper_init(dev, &nfbdev->helper,
-				 nv_two_heads(dev) ? 2 : 1, 4);
+				 dev->mode_config.num_crtc, 4);
 	if (ret) {
 		kfree(nfbdev);
 		return ret;


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