From: Ralf Baechle <ralf@linux-mips.org>
To: Ashish anand <ashish.anand@inspiretech.com>
Cc: linux-mips@linux-mips.org
Subject: Re: Any complications of using CONFIG_MIPS_UNCACHED..?
Date: Tue, 27 May 2003 11:26:49 +0200 [thread overview]
Message-ID: <20030527092649.GB23296@linux-mips.org> (raw)
In-Reply-To: <200305210618.h4L6HqI9006634@smtp.inspirtek.com>
On Wed, May 21, 2003 at 11:16:49AM +0530, Ashish anand wrote:
> I saw a good bit of discussion about CONFIG_MIPS_UNCACHED but
> still i am yet to know...
>
> If I want to use CONFIG_MIPS_UNCACHED (ignoring performance)
> what all the side-effects and any restrictions that linux should
> take care in software ?
>
> I observed something surprising on my R4k mips system(virtually indexed
> caches), after i use this option my driver never got status updation by
> device in transmit and receive decriptors in system memory , Irrespective
> of I (flushed+invalidate) caches or not...
Descriptors sounds like networking. Network descriptors should usually
be stored in uncached or otherwise coherent space that is allocated
through pci_alloc_consistent anyway. If you do that CONFIG_MIPS_UNCACHED
should not make any difference anymore.
> if i don't use CONFIG_MIPS_UNCACHED then before checking status I need to
> (flush+invalidate) cache and whole thing works great...
That's a funny bug. Normally the opposite behaviour would be expected for
a bug ...
Ralf
prev parent reply other threads:[~2003-05-27 9:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-21 5:46 Any complications of using CONFIG_MIPS_UNCACHED..? Ashish anand
2003-05-27 9:26 ` Ralf Baechle [this message]
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