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Date:      Fri, 30 Jan 2009 09:31:47 -0800
From:      Andrew Thompson <thompsa@FreeBSD.org>
To:        Sam Leffler <sam@freebsd.org>
Cc:        arm@freebsd.org
Subject:   Re: busdma problem
Message-ID:  <20090130173147.GC2160@citylink.fud.org.nz>
In-Reply-To: <49833653.60509@freebsd.org>
References:  <20090130072649.GF73709@citylink.fud.org.nz> <49833653.60509@freebsd.org>

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On Fri, Jan 30, 2009 at 09:18:11AM -0800, Sam Leffler wrote:
> Andrew Thompson wrote:
>> Hi,
>> 
>> 
>> I am having an issue with busdma when bounce buffers are used. I have
>> patched _bus_dmamap_sync_bp() to print out the details when a bounce
>> happens and also print the driver buffer before and after.
>> 
>> During normal dma everything is fine,
>> 
>> Before: 0xc7c1ab40 data=c1:4b:a4:80:c0:5d:ed:78:00:00:08:0d:c1:1f:46:78:00:00:20:02:00:00:20:02:
>> [...do dma...]
>> After:  0xc7c1ab40 data=2c:03:4e:00:6f:00:76:00:61:00:74:00:65:00:6c:00:20:00:57:00:69:00:72:00:
>> 
>> The buffer 2c:03:4e:00:... is the correct response from the hardware.
>> When a bounce buffer is used I see the correct data come in and be
>> bcopy'd to my memory region but it is not visible when read later.
>> 
>> Before: 0xc7c29b40 data=c1:50:19:00:c0:5d:ed:f8:00:00:08:0d:c1:1f:46:78:00:00:20:02:00:00:20:02:
>> dma bounced 0x1271000 -> 0xc7c29b40 len=193 data=2c:03:4e:00:6f:00:76:00:61:00:74:00:65:00:6c:00:20:00:57:00:69:00:72:00:
>> After:  0xc7c29b40 data=c1:50:19:00:c0:5d:ed:f8:00:00:08:0d:c1:1f:46:78:00:00:20:02:00:00:20:02:
>> 
>> 
>> This is on an xscale ixp425 with 128m memory, the PCI dma tag is limited
>> to 64m.
>>   
> What device is involved?  Is this on HEAD?

This is usb/ehci. The specific function I am looking at is
usbd_get_string() in usbdi.c, it does a usb request to fill
usb_string_descriptor_t that is a stack variable.

This is on HEAD, a simple way to see it is to run 'usbdevs -v' and see
the vendor/product strings as garbage (sometimes). I have committed a
fix so that total_bounces is actually incremented.

Andrew



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