Re: e1000e: can TIMINCA register be zero?

[Richard Cochran]

On Tue, Apr 19, 2016 at 12:44:08PM +0200, Denys Vlasenko wrote:
> User says it happens on hotplug.

This sounds familiar.

   http://lists.openwall.net/netdev/2016/02/07/90

It also only ever happends in a VM, right?

> In 1000e_config_hwtstamp(), it is initialized before timecounter_init():

...

> By code inspection, e1000e_get_base_timinca() either returns -EINVAL
> and we don't do timecounter_init() and the division/0 location
> is not reached, or e1000e_get_base_timinca(&regval) sets
> nonzero regval. Then we set TIMINCA to this nonzero value.

Right, the register is always set to a non-zero value.
 
> Isn't it fishy that then timecounter_init() -> e1000e_cyclecounter_read()
> -> er32(TIMINCA) sees zero there?

Sure is.

Thanks,
Richard