linux-kernel - Re: [PATCH] Powerpc 8xx CPM

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Date:	Tue, 14 Aug 2012 15:52:27 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Christophe Leroy <christophe.leroy@....fr>
Cc:	Alan Cox <alan@...ux.intel.com>,
	Vitaly Bordug <vitb@...nel.crashing.org>,
	Marcelo Tosatti <marcelo@...ck.org>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] Powerpc 8xx CPM_UART delay in receive

On Tue, 14 Aug 2012 16:26:28 +0200
Christophe Leroy <christophe.leroy@....fr> wrote:

> Hello,
> 
> I'm not sure who to address this Patch to either
> 
> It fixes a delay issue with CPM UART driver on Powerpc MPC8xx.
> The problem is that with the actual code, the driver waits 32 IDLE patterns before returning the received data to the upper level. It means for instance about 1 second at 300 bauds.
> This fix limits to one byte the waiting period.

Take a look how the 8250 does it - I think you want to set the value
based upon the data rate. Your patch will break it for everyone doing
high seed I/O.

Alan
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