Date: Mon, 15 Sep 2003 10:47:22 +0200
From: Jens Axboe <axboe@suse.de>
To: Eduardo Casino <casino_e@terra.es>
Cc: linux-kernel@vger.kernel.org
Subject: Re: SII SATA request size limit
Message-ID: <20030915084722.GD27105@suse.de>
References: <1063399684.1184.7.camel@centinela>
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On Fri, Sep 12 2003, Eduardo Casino wrote:
> Hi All,
> 
> I had a look at the NetBSD pciide.c driver and found this interesting
> bit of code:
> 	
> 	/*
> 	 * Rev. <= 0x01 of the 3112 have a bug that can cause data
> 	 * corruption if DMA transfers cross an 8K boundary.  This is
> 	 * apparently hard to tickle, but we'll go ahead and play it
> 	 * safe.
> 	 */
> 	if (PCI_REVISION(pa->pa_class) <= 0x01) {
> 		sc->sc_dma_maxsegsz = 8192;
> 		sc->sc_dma_boundary = 8192;
> 	}
> 
> This is basically the same as setting hwif->rqsize to 15, but the NetBSD

You can do much much better than that, it's pretty simply to just
restrict the segment size and boundary if you have a controller with
such a bug. And then you get the benefit of the larger requests too,
it's basically not a performance hit at that point.

-- 
Jens Axboe

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