irqchip/gicv3-its: Disable the ITS before initializing it

When starting a kexec/kdump kernel, the GIC ITS will already have been enabled. According to the ARM Generic Interrupt Controller Architecture Specification (GIC architecture Version 3.0 and version 4.0), writing to GITS_BASER<n> or GITS_CBASER is "UNPREDICTABLE" when the ITS is enabled. On Cavium Thunder systems, this prevents the ITS from being initializing in the kexec/kdump kernel, resulting in failure to register/enable interrupts for all devices. The fix is to disable the ITS if it is not already in the disabled state. This allows the ITS to be properly initialized and then re-enabled in the kexec/kdump kernel. Acked-by: Marc Zyngier <[email protected]> Signed-off-by: David Daney <[email protected]> Signed-off-by: Marc Zyngier <[email protected]>
huntrar · Aug 19, 2016 · 7611da8 · 7611da8
1 parent ccd9432
commit 7611da8
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
@@ -1545,7 +1545,12 @@ static int its_force_quiescent(void __iomem *base)
 	u32 val;
 
 	val = readl_relaxed(base + GITS_CTLR);
-	if (val & GITS_CTLR_QUIESCENT)
+	/*
+	 * GIC architecture specification requires the ITS to be both
+	 * disabled and quiescent for writes to GITS_BASER<n> or
+	 * GITS_CBASER to not have UNPREDICTABLE results.
+	 */
+	if ((val & GITS_CTLR_QUIESCENT) && !(val & GITS_CTLR_ENABLE))
 		return 0;
 
 	/* Disable the generation of all interrupts to this ITS */