linux-kernel - [patch 172/176] agp: ensure GART has an address before enabling it

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Date:	Tue, 15 Feb 2011 16:22:20 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Stephen Kitt <steve@....org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kulikov Vasiliy <segooon@...il.com>,
	Florian Mickler <florian@...kler.org>,
	Dave Airlie <airlied@...hat.com>
Subject: [patch 172/176] agp: ensure GART has an address before enabling it

2.6.36-stable review patch.  If anyone has any objections, please let us know.

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

From: Stephen Kitt <steve@....org>

commit a70b95c017e8b518e1e069853355e4e497453dbb upstream.

Some BIOSs (eg.  the AMI BIOS on the Asus P4P800 motherboard) don't
initialise the GART address, and pcibios_assign_resources() can ignore it
because it can be marked as a host bridge (see
https://bugzilla.kernel.org/show_bug.cgi?id=24392#c5 for details).  This
was handled correctly up to 2.6.35, but the pci_enable_device() cleanup in
2.6.36 96576a9e1a0cdb8 ("agp: intel-agp: do not use PCI resources before
pci_enable_device()") means that the kernel tries to enable the GART
before assigning it an address; in such cases the GART overlaps with other
device assignments and ends up being disabled.

This patch fixes https://bugzilla.kernel.org/show_bug.cgi?id=24392

Note that I imagine efficeon-agp.c probably has the same problem, but
I can't test that and I'd like to make sure this patch is suitable for
-stable (since 2.6.36 and 2.6.37 are affected).

Signed-off-by: Stephen Kitt <steve@....org>
Cc: Bjorn Helgaas <bjorn.helgaas@...com>
Cc: Maciej Rutecki <maciej.rutecki@...il.com>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>
Cc: Kulikov Vasiliy <segooon@...il.com>
Cc: Florian Mickler <florian@...kler.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/char/agp/intel-agp.c |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -927,20 +927,14 @@ static int __devinit agp_intel_probe(str
 	dev_info(&pdev->dev, "Intel %s Chipset\n", intel_agp_chipsets[i].name);
 
 	/*
-	* If the device has not been properly setup, the following will catch
-	* the problem and should stop the system from crashing.
-	* 20030610 - hamish@....org
-	*/
-	if (pci_enable_device(pdev)) {
-		dev_err(&pdev->dev, "can't enable PCI device\n");
-		agp_put_bridge(bridge);
-		return -ENODEV;
-	}
-
-	/*
 	* The following fixes the case where the BIOS has "forgotten" to
 	* provide an address range for the GART.
 	* 20030610 - hamish@....org
+	* This happens before pci_enable_device() intentionally;
+	* calling pci_enable_device() before assigning the resource
+	* will result in the GART being disabled on machines with such
+	* BIOSs (the GART ends up with a BAR starting at 0, which
+	* conflicts a lot of other devices).
 	*/
 	r = &pdev->resource[0];
 	if (!r->start && r->end) {
@@ -951,6 +945,17 @@ static int __devinit agp_intel_probe(str
 		}
 	}
 
+	/*
+	* If the device has not been properly setup, the following will catch
+	* the problem and should stop the system from crashing.
+	* 20030610 - hamish@....org
+	*/
+	if (pci_enable_device(pdev)) {
+		dev_err(&pdev->dev, "can't enable PCI device\n");
+		agp_put_bridge(bridge);
+		return -ENODEV;
+	}
+
 	/* Fill in the mode register */
 	if (cap_ptr) {
 		pci_read_config_dword(pdev,


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