[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 3/5] RTC: Add UIP(update in progress) check logic

Actually, in the draft patch, I also think it is unnecessary. And I don't find 
any real use mode to use RTC in this way.
But someone points out that the RTC datasheet allows us to check the update 
cycle by UIP. So we need to support it.

best regards

> -----Original Message-----
> From: Ian Campbell [mailto:Ian.Campbell@xxxxxxxxxx]
> Sent: Tuesday, March 06, 2012 2:36 AM
> To: Zhang, Yang Z
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Jan Beulich
> Subject: Re: [Xen-devel] [PATCH 3/5] RTC: Add UIP(update in progress) check
> logic
> On Mon, 2012-03-05 at 03:25 -0500, Zhang, Yang Z wrote:
> > The UIP(update in progress) is set when RTC is in updating. And the
> > update cycle begins 244us later after UIP is set.
> Not arguing against this patch but OOI how important is it to emulate this
> behaviour to this level of accuracy? On real hardware the UIP tells you that 
> the
> data may not be valid/consistent but I don't think the emulated RTC has that
> property (does it?). Do guest OSes rely on seeing the UIP bit occasionally or 
> have
> you seen a specific issue which caused you to make this change?
> Ian.

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.