From: Mike Frysinger <vapier@gentoo.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH v2 3/9] openrisc: Add cpu files
Date: Thu, 5 Jan 2012 18:15:48 -0500 [thread overview]
Message-ID: <201201051815.49122.vapier@gentoo.org> (raw)
In-Reply-To: <20111222113932.GA4189@chokladfabriken.org>
On Thursday 22 December 2011 06:39:32 Stefan Kristiansson wrote:
> On Thu, Dec 22, 2011 at 10:09:30AM +0100, Michal Simek wrote:
> > Stefan Kristiansson wrote:
> > >+
> > >+void dcache_enable(void)
> > >+{
> > >+ mtspr(SPR_SR, mfspr(SPR_SR) | SPR_SR_DCE);
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> > >+ asm volatile("l.nop");
> >
> > This is interesting. Are there 8 nops?
> > Is there any reason for that? Is it just any waiting?
> > If yes, maybe it will be worth to add any comment.
>
> Yes, the number of nops are kind of arbitrary,
> they are there to add some headroom for the cache
> to startup without any load/stores in flight.
>
> But you are right, a comment about this might be in place.
this is usually why the ISA provides some sort of sync or latch mechanism.
that way code is deterministic instead of being unsettling arbitrary (like it
is here).
-mike
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next prev parent reply other threads:[~2012-01-05 23:15 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-27 5:04 [U-Boot] [PATCH v2 0/9] Add support for the OpenRISC architecture Stefan Kristiansson
2011-11-27 5:04 ` [U-Boot] [PATCH v2 1/9] openrisc: Add architecture header files Stefan Kristiansson
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 2/9] openrisc: Add architecture image support Stefan Kristiansson
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 3/9] openrisc: Add cpu files Stefan Kristiansson
2011-12-22 9:09 ` Michal Simek
2011-12-22 11:39 ` Stefan Kristiansson
2012-01-05 23:15 ` Mike Frysinger [this message]
2012-01-06 13:22 ` Stefan Kristiansson
2012-01-06 19:27 ` Mike Frysinger
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 4/9] openrisc: Add library functions Stefan Kristiansson
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 5/9] openrisc: Add board info printout to cmd_bdinfo Stefan Kristiansson
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 6/9] openrisc: Add support for standalone programs Stefan Kristiansson
2012-01-13 20:29 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 7/9] openrisc: Add openrisc-generic example board Stefan Kristiansson
2012-01-13 20:30 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 8/9] openrisc: Add architecture to MAKEALL Stefan Kristiansson
2012-01-13 20:30 ` Wolfgang Denk
2011-11-27 5:04 ` [U-Boot] [PATCH v2 9/9] openrisc: Add MAINTAINERS entry Stefan Kristiansson
2012-01-13 20:30 ` Wolfgang Denk
2011-12-19 8:20 ` [U-Boot] [PATCH v2 0/9] Add support for the OpenRISC architecture Stefan Kristiansson
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