irqchip: mips-gic: SYNC after enabling GIC region

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
Cc: <stable@vger.kernel.org> # 3.19.x-
Patchwork: https://patchwork.linux-mips.org/patch/17019/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 6ab1d3afec02b39f4d8b26e9e30c280b316de156..48ee1bad473f005fca967d1908b1204fa90773ba 100644 (file)
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -1020,8 +1020,11 @@ 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);