From: James Hogan <james.hogan@imgtec.com>
Date: Sat, 12 Aug 2017 21:36:09 -0700
Subject: [PATCH] irqchip: mips-gic: SYNC after enabling GIC region
References: bnc#1060662
Patch-mainline: 4.12.11
Git-commit: 2c0e8382386f618c85d20cb05e7cf7df8cdd382c

commit 2c0e8382386f618c85d20cb05e7cf7df8cdd382c upstream.

A SYNC is required between enabling the GIC region and actually trying
to use it, even if the first access is a read, otherwise its possible
depending on the timing (and in my case depending on the precise
alignment of certain kernel code) to hit CM bus errors on that first
access.

Add the SYNC straight after setting the GIC base.

[paul.burton@imgtec.com:
  Changes later in this series increase our likelihood of hitting this
  by reducing the amount of code that runs between enabling the GIC &
  accessing it.]

Fixes: a7057270c280 ("irqchip: mips-gic: Add device-tree support")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17019/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/irqchip/irq-mips-gic.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 929f8558bf1c..90e74f9f5f9c 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -1022,8 +1022,11 @@ static int __init gic_of_init(struct device_node *node,
 		gic_len = resource_size(&res);
 	}
 
-	if (mips_cm_present())
+	if (mips_cm_present()) {
 		write_gcr_gic_base(gic_base | CM_GCR_GIC_BASE_GICEN_MSK);
+		/* Ensure GIC region is enabled before trying to access it */
+		__sync();
+	}
 	gic_present = true;
 
 	__gic_init(gic_base, gic_len, cpu_vec, 0, node);
-- 
2.14.2