linux-kernel - Re: [PATCH 3/4] Fix remaining big endian issue of hfcmulti

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Message-ID: <20080805113111.GA6827@pingi.kke.suse.de>
Date:	Tue, 5 Aug 2008 13:31:11 +0200
From:	Karsten Keil <kkeil@...e.de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, isdn4linux@...tserv.isdn4linux.de
Subject: Re: [PATCH 3/4] Fix remaining big endian issue of hfcmulti

On Tue, Aug 05, 2008 at 02:29:48PM +1000, Benjamin Herrenschmidt wrote:
> On Sat, 2008-08-02 at 16:35 +0200, Karsten Keil wrote:
> > The driver was not so bad at big endian at all, only the optimised fifo
> > read/write functions need a fix, with this fix the driver works on
> > a pegasus PPC machine.
> 
> This is however very broken... IE, you should instead use iomap
> and thus get ioreadXX_rep() and writeXX_rep() (XX = 16 or 32) that
> will do the right thing for you. IE, they will do the right amount
> of memory barriers and will avoid the unnecessary double-swapping
> you are doing there.
> 

Thanks for this hint, I didn't know that the repetive versions are
for byte streams and not for eg. transfer of multiple u32.
So it makes things lot easier the code should look like:

	int l = len >> 2;

	if (l) {
		ioread32_rep(hc->pci_membase + A_FIFO_DATA0, data, l);
		data += l << 2;
	}
	if (len & 2) {
		ioread16_rep(hc->pci_membase + A_FIFO_DATA0, data, 1);
		data += 2;
	}
	if (len & 1)
		writeb(*data, hc->pci_membase + A_FIFO_DATA0);

-- 
Karsten Keil
SuSE Labs
ISDN and VOIP development
SUSE LINUX Products GmbH, Maxfeldstr.5 90409 Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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