linux-kernel - Re: [PATCH 3/4] tty: serial: 8250: omap: convert to using cyclic transfers

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Message-ID: <56A3DF17.2070908@linutronix.de>
Date:	Sat, 23 Jan 2016 21:14:15 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Peter Hurley <peter@...leysoftware.com>,
	John Ogness <john.ogness@...utronix.de>,
	gregkh@...uxfoundation.org, vinod.koul@...el.com
Cc:	dan.j.williams@...el.com, tony@...mide.com, nsekhar@...com,
	peter.ujfalusi@...com, dmaengine@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] tty: serial: 8250: omap: convert to using cyclic
 transfers

On 01/22/2016 05:31 PM, Peter Hurley wrote:
> Hi John,
> 
> On 01/22/2016 02:27 AM, John Ogness wrote:
>> Note that an ugly device-tree lookup hack is implemented in order
>> to detect if the sDMA engine is being used. This is necessary
>> because the sDMA driver does not implement pause/resume correctly
>> and therefore requires slightly different logic for the UART
>> driver.
> 
> No, this is not acceptable.
> 
> Please work with Vinod to refine the dma_get_slave_caps() interface
> so that dmaengine drivers that don't provide the _documented_ pause/resume
> support can be identified generically.

But we could implement the pause/resume bits correctly wait until it is
merge and post this and rely on the fact that it works (including error
checking). RMK requested that he wants the UART driver fixed before
touching the DMA driver and this has been done in meantime. So we could
go ahead and add the missing pieces to SDMA.

> Regards,
> Peter Hurley
> 
Sebastian