Re: ehci-hcd affects hda speed

[Rene Herman <rene.herman@keyaccess.nl>]

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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.

Rene

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commit fd96c2b26339f21a66504cb3f36579bb312a8f3b
Author: Rene Herman <rene.herman@gmail.com>
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 <melnikovsky@mail.ru>
    Signed-off-by: Rene Herman <rene.herman@gmail.com>

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)
 			break;
 		}
 		break;
+	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;
 	}
 
 	ehci_reset(ehci);