From mboxrd@z Thu Jan  1 00:00:00 1970
From: Markus =?utf-8?Q?Klotzb=C3=BCcher?= <mk@denx.de>
Date: Fri, 16 May 2008 18:24:49 +0200
Subject: [U-Boot-Users] U-Boot help request for OHCI driver with CPU
	cache on
In-Reply-To: <200805151214.14518.matthias.fuchs@esd-electronics.com> (Matthias
	Fuchs's message of "Thu\, 15 May 2008 12\:14\:14 +0200")
References: <00a901c8b644$c624a1e0$30065e0a@SHZ.ST.COM>
	<87fxskezf3.fsf@denx.de>
	<200805151214.14518.matthias.fuchs@esd-electronics.com>
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Hi Matthias,

Matthias Fuchs <matthias.fuchs@esd-electronics.com> writes:

> On Thursday 15 May 2008 10:37:04 Markus Klotzb?cher wrote:
>> > Could you suggest me how to solve the problem?
>> > Is there any specific part of USB driver that requires cache handling?
>>
>> None that I'm aware of, but I could imagine that enabling caches might
>> cause some kind of problems.
> With U-Boot's current OHCI implementation you will run into trouble at least 
> with cache incoherent CPUs like the 4xx PowerPCs. The 4xx_enet driver
> has been modified to deal with this stuff when data caches are enabled.
> The USB OHCI driver will also need that kind of fixing (making the code very
> ugly). An other approach would be to put the USB DMA accessable memory into
> some non-cached memory. Perhaps this is much more simple.

Thanks for the explanation. Yes I agree that this is likely the
problem.

I'm wondering if the benefits of having the cache enabled is worth the
pain of fixing (= making the code uglier) this at all. I somehow doubt
it.

Best regards

Markus Klotzbuecher

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