linux-kernel - Re: ehci-hcd affects hda speed

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Date:	Mon, 17 Mar 2008 16:00:25 -0800
From:	David Brownell <david-b@...bell.net>
To:	Rene Herman <rene.herman@...access.nl>
Cc:	"Lev A. Melnikovsky" <melnikovsky@...l.ru>,
	Alessandro Suardi <alessandro.suardi@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: ehci-hcd affects hda speed

On Monday 17 March 2008, Rene Herman wrote:
> +       case PCI_VENDOR_ID_VIA:
> +               if (pdev->device == 0x3104 && pdev->revision >= 0x60) {

Unless you have specific docs from VIA saying that this register
isn't revision-specific (at least in the sense that all revisions
after 0x60 define that bit in that way), this should probably be a
switch on pdev->revision and just include the known-safe revisions.

At one point I had a table mapping those revision codes to
specific VIA chips.  Too bad I didn't keep it.  ISTR that the
VT6212 has a newer revision code than the vt8235 southbridge,
and probably not as new as the vt8237 one...

But otherwise, yes -- that's the kind of patch I'd sign off on
after making this comment a bit more informative about how
that 1 usec sleep time creates an amount of PCI bus hogging.

> +                       u8 tmp;
> +
> +                       /* VT6212: EHCI sleep time 10us (default 1) */
> +                       pci_read_config_byte(pdev, 0x4b, &tmp);
> +                       pci_write_config_byte(pdev, 0x4b, tmp | 0x20);
> +               }
> +               break;

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