[PATCH 2/2] ARM: mach-ux500: unlock I&D l2x0 caches before init

[Linus Walleij]

From: Linus Walleij <linus.walleij at linaro.org>

Apparently U8500 U-Boot versions may leave the l2x0 locked down
before executing the kernel. Make sure we unlock it before we
initialize the l2x0. This fixes a performance problem reported
by Jan Rinze.

The l2x0 core has been modified to unlock the l2x0 by default,
but it will not touch the locking registers if the l2x0 was
already enabled, as on the ux500, so we need this quirk to
make sure it is properly turned off.

Cc: stable at kernel.org
Cc: Srinidhi Kasagar <srinidhi.kasagar at stericsson.com>
Cc: Rabin Vincent <rabin.vincent at stericsson.com>
Cc: Adrian Bunk <adrian.bunk at movial.com>
Reported-by: Jan Rinze <janrinze at gmail.com>
Tested-by: Robert Marklund <robert.marklund at stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
 arch/arm/mach-ux500/cpu.c |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-ux500/cpu.c b/arch/arm/mach-ux500/cpu.c
index 1da23bb..8aa104a 100644
--- a/arch/arm/mach-ux500/cpu.c
+++ b/arch/arm/mach-ux500/cpu.c
@@ -99,7 +99,27 @@ static void ux500_l2x0_inv_all(void)
 	ux500_cache_sync();
 }
 
-static int ux500_l2x0_init(void)
+static int __init ux500_l2x0_unlock(void)
+{
+	int i;
+
+	/*
+	 * Unlock Data and Instruction Lock if locked. Ux500 U-Boot versions
+	 * apparently locks both caches before jumping to the kernel. The
+	 * l2x0 core will not touch the unlock registers if the l2x0 is
+	 * already enabled, so we do it right here instead. The PL310 has
+	 * 8 sets of registers, one per possible CPU.
+	 */
+	for (i = 0; i < 8; i++) {
+		writel_relaxed(0x0, l2x0_base + L2X0_LOCKDOWN_WAY_D_BASE +
+			       i * L2X0_LOCKDOWN_STRIDE);
+		writel_relaxed(0x0, l2x0_base + L2X0_LOCKDOWN_WAY_I_BASE +
+			       i * L2X0_LOCKDOWN_STRIDE);
+	}
+	return 0;
+}
+
+static int __init ux500_l2x0_init(void)
 {
 	if (cpu_is_u5500())
 		l2x0_base = __io_address(U5500_L2CC_BASE);
@@ -108,6 +128,9 @@ static int ux500_l2x0_init(void)
 	else
 		ux500_unknown_soc();
 
+	/* Unlock before init */
+	ux500_l2x0_unlock();
+
 	/* 64KB way size, 8 way associativity, force WA */
 	l2x0_init(l2x0_base, 0x3e060000, 0xc0000fff);
 
-- 
1.7.3.2