AT91: Fix power-saving in idle-mode on 926T processors

Hej Peter,

On 2011-01-10 16:05:36, Peter Korsgaard wrote:

On Thu, Oct 7, 2010 at 9:44 PM, Anders Larsen [off-list ref] wrote:

quoted

According to Atmel, their 926T processors (AT91 post RM9200) requires
'Wait for Interrupt' mode be entered right after disabling the processor clock
in order to minimise current consumption when idle, so do both provided we're
not running on a 920T (an RM9200).

Is there a known interaction with this and the JTAG controller?

indeed there is - disabling the processor clock blocks JTAG debugging.

I haven't had time to look closer into it yet, but with this applied
I can no longer access an Altera FPGA on a chain shared with a 9G45
through Quartus.

If you boot with the kernel parameter "nohlt", arch_idle() is not called,
and JTAG should work again (but of course power consumption will be
substantially higher).

This was noted by Uwe Kleine-K?nig in https://lkml.org/lkml/2010/5/5/342

Cheers
Anders