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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)
+ 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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