From: Mike Frysinger <vapier@gentoo.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH v2 3/9] openrisc: Add cpu files
Date: Fri, 6 Jan 2012 14:27:18 -0500 [thread overview]
Message-ID: <201201061427.18815.vapier@gentoo.org> (raw)
In-Reply-To: <20120106132254.GA5499@chokladfabriken.org>
On Friday 06 January 2012 08:22:54 Stefan Kristiansson wrote:
> On Thu, Jan 05, 2012 at 06:15:48PM -0500, Mike Frysinger wrote:
> > 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).
>
> The OpenRISC ISA does provide synch mechanisms, but they are unfortunately
> optional and not supported by the (currently) only open implementation
> (or1200).
sounds like a CONFIG knob for people :). i imagine the # of nop's require
depends heavily on how the core is laid out in hardware, the speed, etc...
-mike
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next prev parent reply other threads:[~2012-01-06 19:27 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
2012-01-06 13:22 ` Stefan Kristiansson
2012-01-06 19:27 ` Mike Frysinger [this message]
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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