linux-kernel - [PATCH] iommu/amd: Increase timeout waiting for GA log enablement

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Message-Id: <20220520102214.12563-1-joro@8bytes.org>
Date:   Fri, 20 May 2022 12:22:14 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Joerg Roedel <jroedel@...e.de>,
        "D. Ziegfeld" <dzigg@...teo.de>,
        Jörg-Volker Peetz <jvpeetz@....de>
Subject: [PATCH] iommu/amd: Increase timeout waiting for GA log enablement

From: Joerg Roedel <jroedel@...e.de>

On some systems it can take a long time for the hardware to enable the
GA log of the AMD IOMMU. The current wait time is only 0.1ms, but
testing showed that it can take up to 14ms for the GA log to enter
running state after it has been enabled.

Sometimes the long delay happens when booting the system, sometimes
only on resume. Adjust the timeout accordingly to not print a warning
when hardware takes a longer than usual.

There has already been an attempt to fix this with commit

	9b45a7738eec ("iommu/amd: Fix loop timeout issue in iommu_ga_log_enable()")

But that commit was based on some wrong math and did not fix the issue
in all cases.

Cc: "D. Ziegfeld" <dzigg@...teo.de>
Cc: Jörg-Volker Peetz <jvpeetz@....de>
Fixes: 8bda0cfbdc1a ("iommu/amd: Detect and initialize guest vAPIC log")
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/amd/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index b4a798c7b347..d8060503ba51 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -84,7 +84,7 @@
 #define ACPI_DEVFLAG_LINT1              0x80
 #define ACPI_DEVFLAG_ATSDIS             0x10000000
 
-#define LOOP_TIMEOUT	100000
+#define LOOP_TIMEOUT	2000000
 /*
  * ACPI table definitions
  *
-- 
2.36.1