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

-----Original Message-----
From: Jamie Iles [mailto:jamie at jamieiles.com]
Sent: Monday, February 07, 2011 7:59 AM
To: John Linn
Cc: Jamie Iles; linux-arm-kernel at lists.infradead.org;

linux-kernel at vger.kernel.org;

linux at arm.linux.org.uk; catalin.marinas at arm.com; glikely at secretlab.ca;

Kiran Sutariya

Subject: Re: [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

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

quoted

+{
+	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));

quoted

quoted

quoted

+
+	if (timer->mode == CLOCK_EVT_MODE_ONESHOT) {
+
+		/* Disable the counter as it would keep running.

*/

quoted

quoted

quoted

+		ctrl_reg = xttcpss_read(timer->base_addr +
+

XTTCPSS_CNT_CNTRL_OFFSET);

quoted

quoted

quoted

+		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

quoted

quoted

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.

quoted

quoted

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

Thanks, appreciate that help as I'm still learning more on the clock
mgmt.

Sounds good, I can stop it and test that.

-- John

This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately.