irqchip/versatile-fpga: Apply clear-mask earlier

BugLink: https://bugs.launchpad.net/bugs/1875905

commit 6a214a28 upstream.

Clear its own IRQs before the parent IRQ get enabled, so that the
remaining IRQs do not accidentally interrupt the parent IRQ controller.

This patch also fixes a reboot bug on OX820 SoC, where the remaining
rps-timer IRQ raises a GIC interrupt that is left pending. After that,
the rps-timer IRQ is cleared during driver initialization, and there's
no IRQ left in rps-irq when local_irq_enable() is called, which evokes
an error message "unexpected IRQ trap".

Fixes: bdd272cb ("irqchip: versatile FPGA: support cascaded interrupts from DT")
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200321133842.2408823-1-mans0n@gorani.runSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/irqchip/irq-versatile-fpga.c

@@ -211,6 +211,9 @@ int __init fpga_irq_of_init(struct device_node *node,
 	if (of_property_read_u32(node, "valid-mask", &valid_mask))
 		valid_mask = 0;
 
+	writel(clear_mask, base + IRQ_ENABLE_CLEAR);
+	writel(clear_mask, base + FIQ_ENABLE_CLEAR);
+
 	/* Some chips are cascaded from a parent IRQ */
 	parent_irq = irq_of_parse_and_map(node, 0);
 	if (!parent_irq) {
@@ -225,9 +228,6 @@ int __init fpga_irq_of_init(struct device_node *node,
 	fpga_irq_init(base, node->name, 0, parent_irq, valid_mask, node);
 #endif
 
-	writel(clear_mask, base + IRQ_ENABLE_CLEAR);
-	writel(clear_mask, base + FIQ_ENABLE_CLEAR);
-
 	/*
 	 * On Versatile AB/PB, some secondary interrupts have a direct
 	 * pass-thru to the primary controller for IRQs 20 and 22-31 which need