linux-kernel - Re: [PATCH 1/5] spi: introduce mmap read support for spi flash devices

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Date:	Wed, 16 Sep 2015 15:38:09 +0530
From:	Vignesh R <vigneshr@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	<hramrach@...il.com>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mtd@...ts.infradead.org>, <linux-spi@...r.kernel.org>
Subject: Re: [PATCH 1/5] spi: introduce mmap read support for spi flash
 devices



On 09/15/2015 12:07 AM, Mark Brown wrote:
> On Fri, Sep 04, 2015 at 01:59:58PM +0530, Vignesh R wrote:
>> In addition to providing direct access to SPI bus, some spi controller
>> hardwares (like ti-qspi) provide special memory mapped port
>> to accesses SPI flash devices in order to increase read performance.
>> This means the controller can automatically send the SPI signals
>> required to read data from the SPI flash device.
> 
> Sorry, also meant to say here: as I kind of indicated in response to the
> flash patch I'd expect to see the SPI core know something about this and
> export an API for this which is integrated with things like the existing
> message queue.
> 


Adding an API to SPI core makes sense to me. This can take care of spi
bus locking and runtime pm.
But, I didn't get how to integrate with existing message queue. Memory
mapped read by-passes message queue of SPI core. Could you please
explain a bit more on integrating with message queue? Did you mean
locking the existing message queue when memory mapped read is being
requested?


Thanks,
Vignesh
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