[ 3.5.y.z extended stable ] Patch "IOMMU, AMD Family15h Model10-1Fh erratum 746 Workaround" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    IOMMU, AMD Family15h Model10-1Fh erratum 746 Workaround

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From f8a6e00b5ebf1e478ba78e6242d4cee1bac301a9 Mon Sep 17 00:00:00 2001
From: Suravee Suthikulpanit <suravee.suthikulpanit at amd.com>
Date: Thu, 24 Jan 2013 13:17:53 -0600
Subject: [PATCH] IOMMU, AMD Family15h Model10-1Fh erratum 746 Workaround

commit 318fe782539c4150d1b8e4e6c9dc3a896512cb8a upstream.

The IOMMU may stop processing page translations due to a perceived lack
of credits for writing upstream peripheral page service request (PPR)
or event logs. If the L2B miscellaneous clock gating feature is enabled
the IOMMU does not properly register credits after the log request has
completed, leading to a potential system hang.

BIOSes are supposed to disable L2B micellaneous clock gating by setting
L2_L2B_CK_GATE_CONTROL[CKGateL2BMiscDisable](D0F2xF4_x90[2]) = 1b. This
patch corrects that for those which do not enable this workaround.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit at amd.com>
Acked-by: Borislav Petkov <bp at suse.de>
Signed-off-by: Joerg Roedel <joro at 8bytes.org>
[ herton: adjust context ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/iommu/amd_iommu_init.c |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index a33612f..eadc6b5 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1002,6 +1002,38 @@ static void __init free_iommu_all(void)
 }

 /*
+ * Family15h Model 10h-1fh erratum 746 (IOMMU Logging May Stall Translations)
+ * Workaround:
+ *     BIOS should disable L2B micellaneous clock gating by setting
+ *     L2_L2B_CK_GATE_CONTROL[CKGateL2BMiscDisable](D0F2xF4_x90[2]) = 1b
+ */
+static void __init amd_iommu_erratum_746_workaround(struct amd_iommu *iommu)
+{
+	u32 value;
+
+	if ((boot_cpu_data.x86 != 0x15) ||
+	    (boot_cpu_data.x86_model < 0x10) ||
+	    (boot_cpu_data.x86_model > 0x1f))
+		return;
+
+	pci_write_config_dword(iommu->dev, 0xf0, 0x90);
+	pci_read_config_dword(iommu->dev, 0xf4, &value);
+
+	if (value & BIT(2))
+		return;
+
+	/* Select NB indirect register 0x90 and enable writing */
+	pci_write_config_dword(iommu->dev, 0xf0, 0x90 | (1 << 8));
+
+	pci_write_config_dword(iommu->dev, 0xf4, value | 0x4);
+	pr_info("AMD-Vi: Applying erratum 746 workaround for IOMMU at %s\n",
+		dev_name(&iommu->dev->dev));
+
+	/* Clear the enable writing bit */
+	pci_write_config_dword(iommu->dev, 0xf0, 0x90);
+}
+
+/*
  * This function clues the initialization function for one IOMMU
  * together and also allocates the command buffer and programs the
  * hardware. It does NOT enable the IOMMU. This is done afterwards.
@@ -1062,6 +1094,8 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
 	if (iommu->cap & (1UL << IOMMU_CAP_NPCACHE))
 		amd_iommu_np_cache = true;

+	amd_iommu_erratum_746_workaround(iommu);
+
 	return pci_enable_device(iommu->dev);
 }

--
1.7.9.5