[PATCH 1/1] ARM: imx: clk-pllv3: change wait method for PLL lock

Peter Chen peter.chen at freescale.com
Thu Jun 6 22:53:21 EDT 2013

On Thu, Jun 06, 2013 at 02:16:47PM +0200, Uwe Kleine-König wrote:
> Hello
> [added jstultz to Cc:]
> On Thu, Jun 06, 2013 at 02:55:26PM +0800, Peter Chen wrote:
> > For tickless system, the jiffies may be updated long time (>20ms).
> ... may not be updated for a long time ... ?
> > At high loading system, the current waiting method will cause waiting
> > timeout, and cause a kernel dump at below case.
> > After timeout = jiffies + msecs_to_jiffies(10),
> > the timer interrupt occurs, it updates jiffies (eg,  + 2 jiffies),
> > then return back from interrupt, the time between above operations
> > are tiny, the PLL is still not locked, but the timeout condition is satisfied.
> Hmm, I admit I didn't follow the tickless stuff, but still I wonder if
> the analysis is right. I thought on tickless jiffies are updated as
> before by the boot cpu that cannot run in tickless mode?
> Anyhow, this only affects the commit log, not the problem.

I add jiffies print at irq_exit (kernel/softirq.c), and it
is not updated every jiffies.

Meanwhile, I ran out this PLL Lock timeout issue with
iperf test using usb ethernet gadget at current code (v3.5.7 kernel).
After using udelay, this issue is disappeared.


Best Regards,
Peter Chen

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