| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.18 33/61] ARM: mvebu: completely disable hardware I/O coherency | Date | Tue, 27 Jan 2015 17:26:45 -0800 |
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3.18-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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@free-electrons.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- 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)
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