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List:       linux-arm-kernel
Subject:    RE: [linux-usb-devel] RE: What does this code snippet check for?
From:       "Yang, Neil L" <neil.l.yang () intel ! com>
Date:       2001-06-29 19:55:00
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Hi,

I realized what could be the cause of these errors.  I'm trying to use the
2.4.5 usb drivers with the 2.4.4 kernel, and I had thought I made the
correct changes to allow this to happen, but in fact, left off the very
important step of copying the new file "pci-sa1111.c" over... doh!  This
file contains functions to compensate for the hardware bug.  Could you
kindly tell me how I can now modify the Makefiles to include this file into
the 2.4.4 kernel?  

Thanks!
Neil

-----Original Message-----
From: David Brownell [mailto:david-b@pacbell.net]
Sent: Friday, June 29, 2001 7:33 AM
To: Yang, Neil L
Subject: Re: [linux-usb-devel] RE: What does this code snippet check
for?


Someone mentioned a flag that had to be passed down to the
allocator ... can you just add GFP_DMA to SLAB_FLAGS?

- Dave


----- Original Message -----
From: "Yang, Neil L" <neil.l.yang@intel.com>
To: "'John Dorsey'" <john+@cs.cmu.edu>; "Yang, Neil L"
<neil.l.yang@intel.com>
Cc: "Linux-Arm-Kernel-Mailing-List (E-Mail)"
<linux-arm-kernel@lists.arm.linux.org.uk>;
<linux-usb-devel@lists.sourceforge.net>
Sent: Thursday, June 28, 2001 10:19 PM
Subject: [linux-usb-devel] RE: What does this code snippet check for?


> Hi,
>
> Thanks for the info.
> You mentioned that modern kernels should be allocating DMA-safe buffers
from
> a region in RAM known to be safe from this bug.  I'm actually getting that
> warning, but I'm using linux 2.4.5-rmk6-np1 kernel, on an
> assabet/neponset-like board.  Do you know where the kernel allocates this
> region, or how I could get around this problem?
>
> Thanks again,
> Neil
>
> -----Original Message-----
> From: John Dorsey [mailto:john+@cs.cmu.edu]
> Sent: Thursday, June 28, 2001 9:33 PM
> To: Yang, Neil L
> Cc: Linux-Arm-Kernel-Mailing-List (E-Mail);
> 'linux-usb-devel@lists.sourceforge.net'
> Subject: Re: What does this code snippet check for?
>
>
>
> On Thursday, June 28, 2001, at 09:19 PM, Yang, Neil L wrote:
>
> > if( (((unsigned long)td->hwCBP) & 0x100000) ) {
> > printk("td_fill() hwCBP %p, a20!\n", (void *)td->hwCBP);
> >
> > }
>
> See the SA-1111 specification update. DMA transfers having a particular
> address bit set generate an erroneous SDRAM AUTOPRECHARGE command, which
> can result in corruption. (The bit is always A10 on the SDRAM, but from
> the perspective of software, the bit can be in different locations
> depending on the SDRAM row/column geometry.)
>
> Testing just for A20 is insufficient; I think sa1111_check_dma_bug() in
> dma-sa1111.c is more thorough. In modern kernels, SA-1111 drivers should
> be allocating DMA-safe buffers from a region in low SDRAM known to have
> immunity from this bug.
>
> -jd
>
>
> _______________________________________________
> linux-usb-devel@lists.sourceforge.net
> To unsubscribe, use the last form field at:
> http://lists.sourceforge.net/lists/listinfo/linux-usb-devel



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