clocksource/drivers/mediatek: Ack and disable interrupts on suspend

Interrupts are disabled during suspend before this driver disables its
timers. ARM trusted firmware will abort suspend if the timer irq is
pending, so ack and disable the timer interrupt during suspend.
Signed-off-by: Evan Benn <evanbenn@chromium.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210512122528.v4.1.I1d9917047de06715da16e1620759f703fcfdcbcb@changeid

drivers/clocksource/timer-mediatek.c

@@ -241,6 +241,28 @@ static void mtk_gpt_enable_irq(struct timer_of *to, u8 timer)
 	       timer_of_base(to) + GPT_IRQ_EN_REG);
 }
 
+static void mtk_gpt_resume(struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	mtk_gpt_enable_irq(to, TIMER_CLK_EVT);
+}
+
+static void mtk_gpt_suspend(struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	/* Disable all interrupts */
+	writel(0x0, timer_of_base(to) + GPT_IRQ_EN_REG);
+
+	/*
+	 * This is called with interrupts disabled,
+	 * so we need to ack any interrupt that is pending
+	 * or for example ATF will prevent a suspend from completing.
+	 */
+	writel(0x3f, timer_of_base(to) + GPT_IRQ_ACK_REG);
+}
+
 static struct timer_of to = {
 	.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
 
@@ -286,6 +308,8 @@ static int __init mtk_gpt_init(struct device_node *node)
 	to.clkevt.set_state_oneshot = mtk_gpt_clkevt_shutdown;
 	to.clkevt.tick_resume = mtk_gpt_clkevt_shutdown;
 	to.clkevt.set_next_event = mtk_gpt_clkevt_next_event;
+	to.clkevt.suspend = mtk_gpt_suspend;
+	to.clkevt.resume = mtk_gpt_resume;
 	to.of_irq.handler = mtk_gpt_interrupt;
 
 	ret = timer_of_init(node, &to);