linux-kernel - Re: Fwd: Linux - AMD SB950 USB Regression

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Date:	Sat, 19 Jan 2013 15:47:53 +0100
From:	dAgeCKo <dagecko@...e.fr>
To:	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, Shane Huang <Shane.Huang@....com>,
	Jörg Rödel <joro@...tes.org>
Subject: Re: Fwd: Linux - AMD SB950 USB Regression

Le 17/01/2013 22:36, Borislav Petkov a écrit :

>
> So, there seems to be some serious breakage with GART on SB9xx. I don't
> know whether this is the platform BIOS or the vendor BIOS causing it
> because the original bug reporter says he observes the issue on an MSI
> board and I'm experiencing this on my favourite bunch ASUS.
>
> So, if you use the GART as an IOMMU, i.e.:
>
> Jan 17 22:08:15 pd kernel: [    0.924063] PCI-DMA: using GART IOMMU.
> Jan 17 22:08:15 pd kernel: [    0.924120] PCI-DMA: Reserving 64MB of IOMMU area in the AGP aperture
>
> USB ports start choking like this:
>
> Jan 17 22:08:15 pd kernel: [    3.229909] usb 4-1: device descriptor read/64, error -32
> Jan 17 22:08:15 pd kernel: [    3.432786] usb 4-1: new high-speed USB device number 3 using ehci-pci
> Jan 17 22:08:15 pd kernel: [    3.534684] usb 4-1: device descriptor read/64, error -32
> Jan 17 22:08:15 pd kernel: [    3.737642] usb 4-1: device descriptor read/64, error -32

Yes, this is exactly what I faced.

>
> I'd go and venture a guess here since I don't have an idea that DMA
> somehow gets busted with the GART and thus the errors.
>
> Now, those boards normally have an IOMMU too so if you go and enable
>
> CONFIG_AMD_IOMMU=y
>
> the problem is gone (we're using the real IOMMU for DMA mapping, etc,
> etc). So dAgeCKo, that would be another thing you could do: try enabling
> the IOMMU in the BIOS and the above CONFIG option and the issue would be
> fixed too.

Here is below, exactly what the guy from MSI said me after I said him a 
BIOS upgrade did resolve my bug:

"The  reacts differently to Win/Linux, but it relies on updates by AMD. 
The new AGESA in the BIOS might had fixes for Linux."

After few researches, it seems that this "BIOS-level" software has 
effectively a special implementation wrapper for Linux (something I 
can't understand why actually). For more reference you can find little 
information here 
(http://www.coreboot.org/data/LinuxBIOS%20AMD%202006%20Final_10-02-2006.pdf).

I can't try the solution you are giving since I can't (and don't want to 
try to) downgrade my BIOS.

Another important thing you might be interested in is that not only my 
USB 2 weren't working. My mainboard ethernet wasn't working to (and was 
resolved with the BIOS upgrade too). The ethernet chip is:

03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. 
RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)

I don't know if that can be related to what you are saying.

>
> At least this fixes it on my box.
>
> To the question "how do we fix the GART issue?" I have no answer and
> would expect more informed opinions from someone else.

Actually I can't tell if I have any GART issues. The only thing I can 
say is that 3D looks to work nicely. However I think I never consumed 
more memory than my graphic card has.

>
> Thanks and HTH.
>

Thanks you too.
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