[PATCH 3.18 35/57] ARM: mvebu: dont set the PL310 in I/O coherency mode when I/O coherency is disabled

Greg Kroah-Hartman
2015-02-03T23:46:57Z

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

commit dcad68876c21bac709b01eda24e39d4410dc36a8 upstream.

Since commit f2c3c67f00 (merge commit that adds commit "ARM: mvebu:
completely disable hardware I/O coherency"), we disable I/O coherency
on Armada EBU platforms.

However, we continue to initialize the coherency fabric, because this
coherency fabric is needed on Armada XP for inter-CPU
coherency. Unfortunately, due to this, we also continued to execute
the coherency fabric initialization code for Armada 375/38x, which
switched the PL310 into I/O coherent mode. This has the effect of
disabling the outer cache sync operation: this is needed when I/O
coherency is enabled to work around a PCIe/L2 deadlock. But obviously,
when I/O coherency is disabled, having the outer cache sync operation
is crucial.

Therefore, this commit fixes the armada_375_380_coherency_init() so
that the PL310 is switched to I/O coherent mode only if I/O coherency
is enabled.

Without this fix, all devices using DMA are broken on Armada 375/38x.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Gregory CLEMENT <gregory.clement@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, 7 insertions(+)

--- a/arch/arm/mach-mvebu/coherency.c
+++ b/arch/arm/mach-mvebu/coherency.c
@@ -342,6 +342,13 @@ static void __init armada_375_380_cohere
arch_ioremap_caller = armada_pcie_wa_ioremap_caller;

/*
+ * We should switch the PL310 to I/O coherency mode only if
+ * I/O coherency is actually enabled.
+ */
+ if (!coherency_available())
+ return;
+
+ /*
* Add the PL310 property "arm,io-coherent". This makes sure the
* outer sync operation is not used, which allows to
* workaround the system erratum that causes deadlocks when