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    SubjectRe: ehci-hcd affects hda speed
    On 18-03-08 01:00, David Brownell wrote:

    > 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.

    I'm looking at a VIA datasheet which says the revision ID for the "VT6212 /
    VT6212L PCI USB2.0 Controller" is simply 0x60. The VT61212L I myself owned
    advertised a revision ID of 0x63 and Lev's VT6212L advertises 0x65.

    The thing is -- you don't necesarily immediately notice this problem. I
    noticed it earlier on an old system, as did Lev, but even if on a modern
    system you may not immediately see an IDE throughput drop, you may still
    have a sucky system.

    With 0x60 documented and 0x63 and 0x65 confirmed as VT6212L, I'd personally
    still go with >= 0x60 and assume either backwards-compatibility or a "don't
    care" definition if some later revision were to not define this hack.

    > 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...

    Some googling seems to indicate that:

    VT6202 = 0x5x (0x50, 0x51 at least)
    VT6212 = 0x6x (0x60, 0x61, 0x63, 0x65 at least)
    VT8235 = 0x82
    VT8237 = 0x86
    VT*800 = 0x90 (KM800Pro, VN800, K8N800, ...)

    Do you want one with 0x6x? I feel it's very likely that everyone on anything
    later will then still have a sucky system. Tons of people with VT8235/VT8237
    around (although not me). Any quick test available for them?

    > 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.

    Version with 0x6x and the somewhat more expansive comment. I'd like to be
    able to test VT8235/VT8237 first though...

    Still totally untested ofcourse.

    commit fd96c2b26339f21a66504cb3f36579bb312a8f3b
    Author: Rene Herman <>
    Date: Tue Mar 18 00:02:16 2008 +0100

    USB: VIA VT6212(L) 10us EHCI sleep time select.

    The VIA VT6212(L) uses a 1us EHCI sleep time by default which hogs
    the bus bad. Use the 10us EHCI spec value instead as suggested by
    Lev A. Melnikovsky.

    CC: Lev A. Melnikovsky <>
    Signed-off-by: Rene Herman <>

    diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
    index 3ba0166..bdc8af9 100644
    --- a/drivers/usb/host/ehci-pci.c
    +++ b/drivers/usb/host/ehci-pci.c
    @@ -152,6 +152,20 @@ static int ehci_pci_setup(struct usb_hcd *hcd)
    + case PCI_VENDOR_ID_VIA:
    + if (pdev->device == 0x3104 && (pdev->revision & 0xf0) == 0x60) {
    + u8 tmp;
    + /*
    + * The VT6212 defaults to a 1us EHCI sleep time which
    + * hogs the bus badly. Setting bit 5 of 0x4B sets the
    + * sleep time to the EHCI standard 10us.
    + */
    + pci_read_config_byte(pdev, 0x4b, &tmp);
    + if (tmp & 0x20)
    + break;
    + pci_write_config_byte(pdev, 0x4b, tmp | 0x20);
    + }
    + break;

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