[U-Boot] [PATCH 01/21] Define new system_restart() and emergency_restart()

[Mike Frysinger]

On Monday, March 07, 2011 18:09:25 Graeme Russ wrote:
> On Tue, Mar 8, 2011 at 9:10 AM, Mike Frysinger <vapier at gentoo.org> wrote:
> > On Monday, March 07, 2011 16:56:31 Moffett, Kyle D wrote:
> >> On Mar 07, 2011, at 16:40, Mike Frysinger wrote:
> >> > On Monday, March 07, 2011 12:37:22 Kyle Moffett wrote:
> >> >> +  udelay(50000);
> >> > 
> >> > this doesnt sit well with me.  i dont see why this matters ... we dont
> >> > have any delays today, and i dont think we should introduce any.
> >> 
> >> Actually, several architectures had a printf()+udelay() already.  (i386
> >> and ARM, IIRC).  Since I was moving the printf() to common code I
> >> figured I'd better move the udelay() as well.
> >> 
> >> I believe they had comments to the effect of "This udelay() prevents
> >> garbage on the serial console while rebooting", I would guess because it
> >> gives the FIFO time to finish flushing.
> > 
> > Blackfin specifically does not do this.  personally, a half baked uart
> > char is preferable to a (imo) useless hardcoded delay.  i wonder if they
> > picked a number that seems to work, or actually calculated it based on
> > the slowest baud times the deepest fifo times the extra bits
> > (parity/stop/etc...).  i'd suspect the former which means this is even
> > dumber.
> > 
> >> I can move it back to the individual architectures if you'd like.
> > 
> > if we cant agree to simply punt it, then yes, please do.  or make it a
> > config option so board porters can opt out, and default it to on for
> > only the existing arches.
> 
> Is there any way we could detect that the UART FIFO is empty and wait on
> that condition (with a timeout in case the FIFO is never emptied)?

that would require extending the serial API to add a new func, have each 
serial driver implement (i'm pretty sure most serial devices out there expose 
a bit to poll such status), and then having the code call it.  i'm not saying 
it cant be done, just outlining the requirements.

although i vaguely recall that Wolfgang is against this sort of thing since it 
kind of goes against the KISS principle ...
-mike
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