Re: [patch v2 1/2] at91_udc.c read_fifo timing issue

Re: [patch v2 1/2] at91_udc.c read_fifo timing issue

[Remy Bohmer]

Hi Harro,

2010/1/29 Harro Haan <hrhaan@gmail.com>:
> This solves the read_fifo timing issue for example seen with CDC Ethernet.
> See the comments below for more info.
>
> Signed-off-by: Harro Haan <hrhaan@gmail.com>
> ---
>  drivers/usb/gadget/at91_udc.c |   46 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 42 insertions(+), 4 deletions(-)
>
Acked-by: Remy Bohmer <linux@bohmer.net>

RE: [patch v2 2/2] at91_udc.c use spinlocks instead of local_irq_xxx

[H Hartley Sweeten]

On Friday, January 29, 2010 9:21 AM, Harro Haan wrote:
>
> The locking code of this driver is reworked for preempt-rt.
>
> Signed-off-by: Harro Haan <hrhaan@gmail.com>
> ---
>  drivers/usb/gadget/at91_udc.c |  139 ++++++++++++++++++++++++++++--------------
>  drivers/usb/gadget/at91_udc.h |    1 
>  2 files changed, 94 insertions(+), 46 deletions(-)

Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>

Re: [patch v2 1/2] at91_udc.c read_fifo timing issue

[Ryan Mallon]

Remy Bohmer wrote:
> Hi Harro,
> 
> 2010/1/29 Harro Haan <hrhaan@gmail.com>:
>> This solves the read_fifo timing issue for example seen with CDC Ethernet.
>> See the comments below for more info.
>>
>> Signed-off-by: Harro Haan <hrhaan@gmail.com>
>> ---
>>  drivers/usb/gadget/at91_udc.c |   46 ++++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 42 insertions(+), 4 deletions(-)
>>
> Acked-by: Remy Bohmer <linux@bohmer.net>

Can I get your Acked-by for my patch also Remy?

Harro, I can either submit my patch to the patch system separately, or
you can put it through with your series with my From/Signed-off-by tag
on it.

~Ryan

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Re: [patch v2 1/2] at91_udc.c read_fifo timing issue

[Anti Sullin]

Harro Haan wrote:
 > This solves the read_fifo timing issue for example seen with CDC 
Ethernet.
[...]

Still this bug not fixed?
I sent almost the same fix and a lot of debug info with description of 
the issue and the critical path of the timing to linux-arm-kernel on 
2009-03-25 ( 
http://lists.arm.linux.org.uk/lurker/message/20090325.150843.f515c02f.en.html 
) and we had an off-list discussion with David Brownell about another 
udc patch on 2009-06-19 that later turned out to be the same issue.

This fix has solved the problems on our devices and we've been using it 
for almost a year now.

About Harro's patch:
* why are the marker1 and marker2 comments necessary to be included?
* maybe you should just link to the mailing list and/or move the long 
comment to patch description instead adding a page-long comment to code; 
just leave a small comment to explain why the work-around is needed so 
that nobody would optimize it away?
* Is the error check and warning message necessary after we've got rid
of the problem? Won't it add problems - as I found out, the first csr
read (that comes too early) may return bogus data, you should not use 
its result at all.

-- 
Anti Sullin
Embedded Software Engineer
Artec Design LLC
Teaduspargi 6/2, 12618, Tallinn, Estonia
http://www.artecdesign.ee