[PATCH 3/4] ARM: Xilinx: Adding timer support to the platform

On Mon, Feb 07, 2011 at 07:16:01AM -0700, John Linn wrote:

quoted

-----Original Message-----
From: Jamie Iles [mailto:jamie at jamieiles.com]
Sent: Saturday, February 05, 2011 6:04 PM
To: John Linn
Cc: linux-arm-kernel at lists.infradead.org;

linux-kernel at vger.kernel.org; linux at arm.linux.org.uk;

quoted

catalin.marinas at arm.com; glikely at secretlab.ca; Kiran Sutariya
Subject: Re: [PATCH 3/4] ARM: Xilinx: Adding timer support to the

platform

quoted

Hi John,

A couple more nitpicks.

Jamie

On Sat, Feb 05, 2011 at 09:17:16AM -0700, John Linn wrote:

quoted

+static irqreturn_t xttcpss_clock_event_interrupt(int irq, void

*dev_id)

quoted

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+{
+	struct clock_event_device *evt = &xttcpss_clockevent;
+	struct xttcpss_timer *timer = dev_id;
+	u32 ctrl_reg;
+
+	/* Acknowledge the interrupt and call event handler */
+	xttcpss_write(timer->base_addr + XTTCPSS_ISR_OFFSET,
+		xttcpss_read(timer->base_addr + XTTCPSS_ISR_OFFSET));
+
+	if (timer->mode == CLOCK_EVT_MODE_ONESHOT) {
+
+		/* Disable the counter as it would keep running. */
+		ctrl_reg = xttcpss_read(timer->base_addr +
+					XTTCPSS_CNT_CNTRL_OFFSET);
+		ctrl_reg |= ~(XTTCPSS_CNT_CNTRL_ENABLE_MASK);

The clock events framework should reprogram the next event so you

don't

quoted

actually need to disable the timer here.  Once the event handler has
been called the timer will be reenabled with a new period, and as

we're

quoted

running with interrupts disabled here we don't need to stop the timer.

What about if there's not another event to be started?

Then the clockevents code can set the mode to CLOCK_EVT_MODE_SHUTDOWN 
and this should disable the timer.  For NOHZ, AFAICT the 
clockevents/tick code will make sure that the next tick always falls 
within your max_delta_ns.

Jamie