[patch 2.5.65] ehci-hcd, don't use PCI MWI

[patch 2.5.65] ehci-hcd, don't use PCI MWI

[David Brownell]

[-- Attachment #1: Type: text/plain, Size: 451 bytes --]

Hi,

Some users have been sending init logs for Athlon kernels that
include PCI warning messages about the PCI cache line size
getting set incorrectly ... where the kernel thinks that the
right value is 16 bytes.  Since 64 bytes is the right number,
it's dangerous to enable MWI on such systems.

This patch stops trying to use MWI; it's a workaround for the
misbehavior of that PCI cacheline-setting code.  Please apply
to 2.5 and 2.4 trees.

- Dave

[-- Attachment #2: ehci-0319a.patch --]
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--- 1.45/drivers/usb/host/ehci-hcd.c	Mon Feb 24 03:30:38 2003
+++ edited/drivers/usb/host/ehci-hcd.c	Wed Mar 19 07:05:33 2003
@@ -432,7 +432,11 @@
 	}
 
 	/* help hc dma work well with cachelines */
-	pci_set_mwi (ehci->hcd.pdev);
+	/* NOTE:  disabled until it works reliably ... some x86/Athlon
+	 * kernels are thinking 16 byte cachelines, not 64 byte ones,
+	 * so clearly the MWI prep logic is wrong.
+	 */
+	// pci_set_mwi (ehci->hcd.pdev);
 
 	/* clear interrupt enables, set irq latency */
 	temp = readl (&ehci->regs->command) & 0xff;

Re: [patch 2.5.65] ehci-hcd, don't use PCI MWI

[Jeff Garzik]

On Wed, Mar 19, 2003 at 07:21:42AM -0800, David Brownell wrote:
> Hi,
> 
> Some users have been sending init logs for Athlon kernels that
> include PCI warning messages about the PCI cache line size
> getting set incorrectly ... where the kernel thinks that the
> right value is 16 bytes.  Since 64 bytes is the right number,
> it's dangerous to enable MWI on such systems.
> 
> This patch stops trying to use MWI; it's a workaround for the
> misbehavior of that PCI cacheline-setting code.  Please apply
> to 2.5 and 2.4 trees.

Please don't -- Ivan has a patch for this, let's get that in instead.

We all acknowledge your patch is a workaround, but this sort of fix does
not belong in the mainstream kernel.  We want to fix it The Right
Way(tm), once.  And since a patch already exists for this...

We need to get IvanK's extended-save-restore-state patch in, too.

Ivan, would you be up for a repost on lkml?

	Jeff

Re: [patch 2.5.65] ehci-hcd, don't use PCI MWI

[David Brownell]

Jeff Garzik wrote:
> On Wed, Mar 19, 2003 at 07:21:42AM -0800, David Brownell wrote:
> 
>>Hi,
>>
>>Some users have been sending init logs for Athlon kernels that
>>include PCI warning messages about the PCI cache line size
>>getting set incorrectly ... where the kernel thinks that the
>>right value is 16 bytes.  Since 64 bytes is the right number,
>>it's dangerous to enable MWI on such systems.
>>
>>This patch stops trying to use MWI; it's a workaround for the
>>misbehavior of that PCI cacheline-setting code.  Please apply
>>to 2.5 and 2.4 trees.
> 
> 
> Please don't -- Ivan has a patch for this, let's get that in instead.

I'd be happy with that, except on the 2.4 trees where we haven't
seen such a patch yet.  (So Greg -- please hold off on this
for 2.5 unless/until it becomes clear Ivan's patch won't happen.)

> We all acknowledge your patch is a workaround, but this sort of fix does
> not belong in the mainstream kernel.  We want to fix it The Right
> Way(tm), once.  And since a patch already exists for this...

Yep, I figured CC'ing LKML would help move things forward ... :)

- Dave



> We need to get IvanK's extended-save-restore-state patch in, too.
> 
> Ivan, would you be up for a repost on lkml?
> 
> 	Jeff
> 
> 
> 
> 

Re: [patch 2.5.65] ehci-hcd, don't use PCI MWI

[Ivan Kokshaysky]

On Wed, Mar 19, 2003 at 07:53:35AM -0800, David Brownell wrote:
> Jeff Garzik wrote:
> > Please don't -- Ivan has a patch for this, let's get that in instead.
> 
> I'd be happy with that, except on the 2.4 trees where we haven't
> seen such a patch yet.  (So Greg -- please hold off on this
> for 2.5 unless/until it becomes clear Ivan's patch won't happen.)

Hopefully I'll post the updated patch tomorrow.
Right now I'm chasing down weird problem - 2.5.65 broke networking
on one of my boxes. So far I figured out that reverting serial/core
changes fixes that. Incredibly...

Ivan.

Re: [patch 2.5.65] ehci-hcd, don't use PCI MWI

[Greg KH]

On Wed, Mar 19, 2003 at 07:53:35AM -0800, David Brownell wrote:
> 
> I'd be happy with that, except on the 2.4 trees where we haven't
> seen such a patch yet.  (So Greg -- please hold off on this
> for 2.5 unless/until it becomes clear Ivan's patch won't happen.)

I'll hold off for both 2.5 and 2.4, as Ivan's patch should go into both
kernels.

thanks,

greg k-h