linux-kernel - Re: [PATCH V2 2/2] mtd: spi-nor: Bindings for Cadence Quad SPI Flash Controller driver.

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Message-ID: <54B41BED.5090809@opensource.altera.com>
Date:	Mon, 12 Jan 2015 13:09:33 -0600
From:	Graham Moore <grmoore@...nsource.altera.com>
To:	Rob Herring <robherring2@...il.com>
CC:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alan Tull <atull@...nsource.altera.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Yves Vandervennet <yvanderv@...nsource.altera.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH V2 2/2] mtd: spi-nor: Bindings for Cadence Quad SPI Flash
 Controller driver.


On 01/08/2015 04:30 PM, Rob Herring wrote:
>
> This controller only works with flash devices and is different than this one:?
>
> Documentation/devicetree/bindings/spi/spi-cadence.txt
>

Yes, it is a different controller and is for flash only.  The docs call 
it the "QSPI Flash Controller".
...

>
> The above binding already uses "is-decoded-cs". Let's not invent something new.
>

OK.
...

>
>>> +- cdns,tshsl-ns : Delay in master reference clocks for the length that the master mode chip select outputs are de-asserted between transactions.
>>> +- cdns,tsd2d-ns : Delay in master reference clocks between one chip select being de-activated and the activation of another.
>>> +- cdns,tchsh-ns : Delay in master reference clocks between last bit of current transaction and deasserting the device chip select (qspi_n_ss_out).
>>> +- cdns,tslch-ns : Delay in master reference clocks between setting qspi_n_ss_out low and first bit transfer.
>
> Aren't these properties probeable at all? We really should have
> standard bindings for this. It seems spi NOR flash devices have gone
> somewhat undocumented, but it is not hard to find examples already in
> use.
>

They are not probeable, afaik.  I don't see these values in any 
probeable info block in the datasheet, only in the AC params table.

I can't find an example of these timing parameters, do you have one in mind?

> Is it master reference clocks or nanoseconds for the units?

Yeah, they are actually nanoseconds in the dts, converted to clocks in 
the driver.  I'll change the docs.

...

Thanks,
Graham
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