[PATCH 2/2] drivers/clocksource/mediatek: Ack and disable interrupts on shutdown

[Evan Benn <evanbenn@chromium.org>]

set_state_shutdown is called during system suspend after interrupts have
been disabled. If the timer has fired in the meantime, there will be
a pending IRQ. So we ack that now and disable the timer. Without this
ARM trusted firmware will abort the suspend due to the pending
interrupt.

Now always disable the IRQ in state transitions, and re-enable in
set_periodic and next_event.

Signed-off-by: Evan Benn <evanbenn@chromium.org>
---

 drivers/clocksource/timer-mediatek-mt6577.c | 49 +++++++++++++--------
 1 file changed, 30 insertions(+), 19 deletions(-)

diff --git a/drivers/clocksource/timer-mediatek-mt6577.c b/drivers/clocksource/timer-mediatek-mt6577.c
index 9e5241d1876d..44598121585c 100644
--- a/drivers/clocksource/timer-mediatek-mt6577.c
+++ b/drivers/clocksource/timer-mediatek-mt6577.c
@@ -54,13 +54,33 @@ static u64 notrace mtk_gpt_read_sched_clock(void)
 	return readl_relaxed(gpt_sched_reg);
 }
 
+static void mtk_gpt_disable_ack_interrupts(struct timer_of *to, u8 timer)
+{
+	u32 val;
+
+	/* Disable interrupts */
+	val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
+	writel(val & ~GPT_IRQ_ENABLE(timer), timer_of_base(to) +
+	       GPT_IRQ_EN_REG);
+
+	/* Ack interrupts */
+	writel(GPT_IRQ_ACK(timer), timer_of_base(to) + GPT_IRQ_ACK_REG);
+}
+
 static void mtk_gpt_clkevt_time_stop(struct timer_of *to, u8 timer)
 {
 	u32 val;
 
+	/* Disable timer */
 	val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
 	writel(val & ~GPT_CTRL_ENABLE, timer_of_base(to) +
 	       GPT_CTRL_REG(timer));
+
+	/* This may be called with interrupts disabled,
+	 * so we need to ack any interrupt that is pending
+	 * Or for example ATF will prevent a suspend from completing.
+	 */
+	mtk_gpt_disable_ack_interrupts(to, timer);
 }
 
 static void mtk_gpt_clkevt_time_setup(struct timer_of *to,
@@ -74,8 +94,10 @@ static void mtk_gpt_clkevt_time_start(struct timer_of *to,
 {
 	u32 val;
 
-	/* Acknowledge interrupt */
-	writel(GPT_IRQ_ACK(timer), timer_of_base(to) + GPT_IRQ_ACK_REG);
+	/* Enable interrupts */
+	val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
+	writel(val | GPT_IRQ_ENABLE(timer),
+	       timer_of_base(to) + GPT_IRQ_EN_REG);
 
 	val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
 
@@ -148,21 +170,6 @@ __init mtk_gpt_setup(struct timer_of *to, u8 timer, u8 option)
 	       timer_of_base(to) + GPT_CTRL_REG(timer));
 }
 
-static void mtk_gpt_enable_irq(struct timer_of *to, u8 timer)
-{
-	u32 val;
-
-	/* Disable all interrupts */
-	writel(0x0, timer_of_base(to) + GPT_IRQ_EN_REG);
-
-	/* Acknowledge all spurious pending interrupts */
-	writel(0x3f, timer_of_base(to) + GPT_IRQ_ACK_REG);
-
-	val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
-	writel(val | GPT_IRQ_ENABLE(timer),
-	       timer_of_base(to) + GPT_IRQ_EN_REG);
-}
-
 static struct timer_of to = {
 	.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
 
@@ -193,6 +200,12 @@ static int __init mtk_gpt_init(struct device_node *node)
 	if (ret)
 		return ret;
 
+	/* In case the firmware left the interrupts enabled
+	 * disable and ack those now
+	 */
+	mtk_gpt_disable_ack_interrupts(&to, TIMER_CLK_SRC);
+	mtk_gpt_disable_ack_interrupts(&to, TIMER_CLK_EVT);
+
 	/* Configure clock source */
 	mtk_gpt_setup(&to, TIMER_CLK_SRC, GPT_CTRL_OP_FREERUN);
 	clocksource_mmio_init(timer_of_base(&to) + GPT_CNT_REG(TIMER_CLK_SRC),
@@ -206,8 +219,6 @@ static int __init mtk_gpt_init(struct device_node *node)
 	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
 					TIMER_SYNC_TICKS, 0xffffffff);
 
-	mtk_gpt_enable_irq(&to, TIMER_CLK_EVT);
-
 	return 0;
 }
 TIMER_OF_DECLARE(mtk_mt6577, "mediatek,mt6577-timer", mtk_gpt_init);
-- 
2.31.0.rc2.261.g7f71774620-goog