linux-kernel - Re: [PATCH 1/2] serial: imx: remove the DMA wait queue

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Message-ID: <20140530090128.GA4380@shlinux1.ap.freescale.net>
Date:	Fri, 30 May 2014 17:01:30 +0800
From:	Huang Shijie <b32955@...escale.com>
To:	"Wang, Jiada (ESD)" <Jiada_Wang@...tor.com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"Behme, Dirk - Bosch" <dirk.behme@...bosch.com>
Subject: Re: [PATCH 1/2] serial: imx: remove the DMA wait queue

On Fri, May 30, 2014 at 09:27:20AM +0000, Wang, Jiada (ESD) wrote:
> Hi Shijie
> 
> After apply this patch into our kernel,
> We are facing data hang issue when sending big size file (2M used in test) to uart port
> Note: Rx port is also keep receiving data.
> 
> After read the implementation of uart_stop(),
> I feel like, stop_tx() is used to perform flow control when like a XOFF is received.
> Which means no data should be dropped, as they may need to be sent out,
> When next start_tx() is called.
> 
> But by calling dmaengine_termiate_all(), the data already be submitted to DMA engine,
> May be lost, thus cause data hang.
> 
> What do you think?
This patch has been reverted by Greg.

I also noticed the data loss issue. 

thanks
Huang Shijie
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