linux-kernel - [PATCH 2/2] arm: socfpga: Set share override bit of the l2 cache controller

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Message-ID: <1416546280-12068-2-git-send-email-dinguyen@opensource.altera.com>
Date:	Thu, 20 Nov 2014 23:04:40 -0600
From:	<dinguyen@...nsource.altera.com>
To:	<linux@....linux.org.uk>
CC:	<dinh.linux@...il.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>
Subject: [PATCH 2/2] arm: socfpga: Set share override bit of the l2 cache controller

From: Dinh Nguyen <dinguyen@...nsource.altera.com>

By not having bit 22 set in the PL310 Auxiliary Control register (shared
attribute override enable) has the side effect of transforming Normal
Shared Non-cacheable reads into Cacheable no-allocate reads.

Coherent DMA buffers in Linux always have a Cacheable alias via the
kernel linear mapping and the processor can speculatively load cache
lines into the PL310 controller. With bit 22 cleared, Non-cacheable
reads would unexpectedly hit such cache lines leading to buffer
corruption.

Signed-off-by: Dinh Nguyen <dinguyen@...nsource.altera.com>
---
 arch/arm/mach-socfpga/socfpga.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-socfpga/socfpga.c b/arch/arm/mach-socfpga/socfpga.c
index 13b1858..afc009f 100644
--- a/arch/arm/mach-socfpga/socfpga.c
+++ b/arch/arm/mach-socfpga/socfpga.c
@@ -105,7 +105,8 @@ static const char *altera_dt_match[] = {
 
 DT_MACHINE_START(SOCFPGA, "Altera SOCFPGA")
 	.l2c_aux_val	= L310_AUX_CTRL_DATA_PREFETCH |
-			  L310_AUX_CTRL_INSTR_PREFETCH,
+			  L310_AUX_CTRL_INSTR_PREFETCH |
+			  L2C_AUX_CTRL_SHARED_OVERRIDE,
 	.l2c_aux_mask	= ~0,
 	.smp		= smp_ops(socfpga_smp_ops),
 	.map_io		= socfpga_map_io,
-- 
2.0.3

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