linux-kernel - Re: [RFC PATCH 0/2] spi: add dual parallel & stacked mode support in Zynq MPSoC GQSPI controller

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Message-ID: <559F824B.70409@topic.nl>
Date:	Fri, 10 Jul 2015 10:28:59 +0200
From:	Mike Looijmans <mike.looijmans@...ic.nl>
To:	Ranjit Waghmode <ranjit.waghmode@...inx.com>, <broonie@...nel.org>,
	<michal.simek@...inx.com>, <soren.brinkmann@...inx.com>,
	<dwmw2@...radead.org>, <computersforpeace@...il.com>,
	<zajec5@...il.com>, <marex@...x.de>, <shijie.huang@...el.com>,
	<juhosg@...nwrt.org>, <ben@...adent.org.uk>
CC:	<harinik@...inx.com>, <linux-kernel@...r.kernel.org>,
	<linux-spi@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
	<punnaia@...inx.com>, <ran27jit@...il.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 0/2] spi: add dual parallel & stacked mode support
 in Zynq MPSoC GQSPI controller

On 09-07-15 14:44, Ranjit Waghmode wrote:
> This series of patches is to add dual parallel and stacked mode support for
> Zynq Ultrascale+ MPSoC GQSPI controller driver.
>
> These are all very high level changes and expected to make an idea clear.
> Comments and suggestions are welcomed.
>
...
>
> What is stacked mode?
> ---------------------
> ZynqMP GQSPI controller supports stacked mode with following functionalities:
> 1) The Generic Quad-SPI controller also supports two SPI flash memories
>     in a shared bus arrangement to reduce IO pin count.
> 2) Separate chip select lines
> 3) Shared I/O lines
> 4) This mode is targeted for increasing the flash memory and no performance
>     improvement when compared with single.

One could also model the stacked mode as having two distinct flash chips with 
separate chip selects and shared lines.
Merging them into a single storage device can be done on block layer or higher 
level. This allows the flash chips to be used in any configuration using 
existing support for concatenating multiple devices.
I think this would be a more generic way of doing this. It also allows much 
more flexibility, for example the devices could be used in a mirror setup, or 
in combination with additional devices on other controllers.


Kind regards,

Mike Looijmans
System Expert

TOPIC Embedded Products
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