This is a note to let you know that I've just added the patch titled
ARM: mvebu: completely disable hardware I/O coherency
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-mvebu-completely-disable-hardware-i-o-coherency.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8f1e8ee28660018a935c7576b9af8ffe1feab54c Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Date: Fri, 16 Jan 2015 17:11:27 +0100
Subject: ARM: mvebu: completely disable hardware I/O coherency
From: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
commit 8f1e8ee28660018a935c7576b9af8ffe1feab54c upstream.
The current hardware I/O coherency is known to cause problems with DMA
coherent buffers, as it still requires explicit I/O synchronization
barriers, which is not compatible with the semantics expected by the
Linux DMA coherent buffers API.
So, in order to have enough time to validate a new solution based on
automatic I/O synchronization barriers, this commit disables hardware
I/O coherency entirely. Future patches will re-enable it.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Lunn <andrew@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mach-mvebu/coherency.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/arch/arm/mach-mvebu/coherency.c
+++ b/arch/arm/mach-mvebu/coherency.c
@@ -398,9 +398,14 @@ static int coherency_type(void)
return type;
}
+/*
+ * As a precaution, we currently completely disable hardware I/O
+ * coherency, until enough testing is done with automatic I/O
+ * synchronization barriers to validate that it is a proper solution.
+ */
int coherency_available(void)
{
- return coherency_type() != COHERENCY_FABRIC_TYPE_NONE;
+ return false;
}
int __init coherency_init(void)
Patches currently in stable-queue which might be from thomas.petazzoni@xxxxxxxxxxxxxxxxxx are
queue-3.18/arm-mvebu-completely-disable-hardware-i-o-coherency.patch
queue-3.18/bus-mvebu-mbus-fix-support-of-mbus-window-13.patch
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