linux-kernel - Re: [PATCH] atmel serial reduce trasmitting window & code style patch

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Date:	Mon, 7 Apr 2008 08:14:24 +0000 (GMT)
From:	Michael Trimarchi <trimarchimichael@...oo.it>
To:	Haavard Skinnemoen <hskinnemoen@...el.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atmel serial reduce trasmitting window & code style patch


Hi,

> Ok, the patch seems to make sense, but your description
> isn't very good...
ok
>   * What problem does this patch solve (I think I know it,
> but I don't
>     want to guess.)
I try to resolve this problem:
The serial is set in interrupt mode 9600, and trasmit a lot of data.
The serial receive data from another device. The receive buffer is
1024 bytes and the trasmit buffer is an XMIT_SIZE. So when the tasklet
start to trasmit, it can loose data.
>   * This patch doesn't really reduce any "TX
> window" since the window
>     simply didn't exist before (or was infinitely long
> or whatever.) I
>     think you should mention that this limitation is a new
> thing.

>   * Why is 32 a good value?
> 
... I don't know a good value, because the tasklet can be preempted,
and the receiving buffer can be fill in background. It is hard to choose
a good value...
> Also, do we need to reschedule the tasklet if we terminate
> the loop
> because of this limit? I think we can get away with not
> doing it since
> the interrupt handler will be triggered as soon as we
> enable the TX
> interrupt. But perhaps we should avoid enabling the
> interrupt and
> schedule the tasklet since we _know_ there's a TX
> interrupt pending?
> 
Ok, you are right, schedule the tasklet is better. I do some
test and post another patch. 

Michael


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