Subject: [PATCH v2 1/5] clocksource: mediatek: do not enable GPT_CLK_EVT when setup

From: [email-masked] (Daniel Lezcano)
Date: Thu, 13 Aug 2015 10:35:16 +0200

On 07/22/2015 10:14 AM, Yingjoe Chen wrote:
> Spurious mtk timer interrupt is noticed at boot and cause kernel
> crash. It seems if GPT is enabled, it will latch irq status even
> when its IRQ is disabled. When irq is enabled afterward, we see
> spurious interrupt.
> Change init flow to only enable GPT_CLK_SRC at mtk_timer_init.
>
> Acked-by: Matthias Brugger <[email-masked]>
> Reviewed-by: Daniel Kurtz <[email-masked]>
> Signed-off-by: Yingjoe Chen <[email-masked]>
> ---
>
> Update to my patch [1], added __init as Daniel suggest. This is the
> only patch that need to change in that series, so I only sent this one.
>
> http://lists.infradead.org/pipermail/linux-mediatek/2015-July/001545.html
>
>   drivers/clocksource/mtk_timer.c | 16 ++++++++++------
>   1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/clocksource/mtk_timer.c b/drivers/clocksource/mtk_timer.c
> index 68ab423..2ba5b66 100644
> --- a/drivers/clocksource/mtk_timer.c
> +++ b/drivers/clocksource/mtk_timer.c
> @@ -156,9 +156,11 @@ static void mtk_timer_global_reset(struct mtk_clock_event_device *evt)
>   	writel(0x3f, evt->gpt_base + GPT_IRQ_ACK_REG);
>   }
>
> -static void
> -mtk_timer_setup(struct mtk_clock_event_device *evt, u8 timer, u8 option)
> +static void __init mtk_timer_setup(struct mtk_clock_event_device *evt,
> +				   u8 timer, u8 option, bool enable)
>   {
> +	u32 val;
> +
>   	writel(TIMER_CTRL_CLEAR | TIMER_CTRL_DISABLE,
>   		evt->gpt_base + TIMER_CTRL_REG(timer));
>
> @@ -167,8 +169,10 @@ mtk_timer_setup(struct mtk_clock_event_device *evt, u8 timer, u8 option)
>
>   	writel(0x0, evt->gpt_base + TIMER_CMP_REG(timer));
>
> -	writel(TIMER_CTRL_OP(option) | TIMER_CTRL_ENABLE,
> -			evt->gpt_base + TIMER_CTRL_REG(timer));
> +	val = TIMER_CTRL_OP(option);
> +	if (enable)
> +		val |= TIMER_CTRL_ENABLE;
> +	writel(val, evt->gpt_base + TIMER_CTRL_REG(timer));

Instead of the 'enable' new option, I prefer a test with 'timer' with a 
comment:

	/*
	 * the timer hw is broken in that way ... bla bla, so we only
	 * enable the clocksource ...
	 */
	if (timer == GPT_CLK_SRC)
		val |= TIMER_CTRL_ENABLE;

That said, can you have a look at commit 1096be08 ?
"clockevents: sun5i: Fix setup_irq init sequence"

first and check if moving the interrupt request after the 
clockevents_config_and_register could fix your issue.

>   }
>
>   static void mtk_timer_enable_irq(struct mtk_clock_event_device *evt, u8 timer)
> @@ -235,12 +239,12 @@ static void __init mtk_timer_init(struct device_node *node)
>   	evt->ticks_per_jiffy = DIV_ROUND_UP(rate, HZ);
>
>   	/* Configure clock source */
> -	mtk_timer_setup(evt, GPT_CLK_SRC, TIMER_CTRL_OP_FREERUN);
> +	mtk_timer_setup(evt, GPT_CLK_SRC, TIMER_CTRL_OP_FREERUN, true);
>   	clocksource_mmio_init(evt->gpt_base + TIMER_CNT_REG(GPT_CLK_SRC),
>   			node->name, rate, 300, 32, clocksource_mmio_readl_up);
>
>   	/* Configure clock event */
> -	mtk_timer_setup(evt, GPT_CLK_EVT, TIMER_CTRL_OP_REPEAT);
> +	mtk_timer_setup(evt, GPT_CLK_EVT, TIMER_CTRL_OP_REPEAT, false);
>   	clockevents_config_and_register(&evt->dev, rate, 0x3,
>   					0xffffffff);

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