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From: Michal Simek <michal.simek@xilinx.com>
To: Mark Brown <broonie@kernel.org>, Michal Simek <michal.simek@xilinx.com>
Cc: linux-kernel@vger.kernel.org, monstr@monstr.eu,
	"Sören Brinkmann" <soren.brinkmann@xilinx.com>,
	linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] spi: xilinx: Use standard num-cs binding
Date: Fri, 27 Mar 2015 11:55:49 +0100	[thread overview]
Message-ID: <2a81c738-f7e2-4387-b04c-05c9892ba8e4@BN1AFFO11FD026.protection.gbl> (raw)
In-Reply-To: <20150308190012.GV28806@sirena.org.uk>

Hi Mark,

On 03/08/2015 08:00 PM, Mark Brown wrote:
> On Fri, Jan 16, 2015 at 01:55:14PM +0100, Michal Simek wrote:
>> Use standard num-cs binding property and setup
>> "xlnx,num-ss-bits" as deprecated.
> 
> Why?  These properties mean different things - num-cs is a bit confused
> and is the total number of available chip selects for the system (which
> could include GPIOs) while num-ss-bits is the size of the bitfield
> (which could include things not actually mapped out properly/successfully 
> or something if the hardware designers were feeling particularly inspired).

I was checking meaning of num-ss-bits and meaning is Number of slaves (taking
explanation from Vivado 2014.4) Range 1-32.
http://www.xilinx.com/support/documentation/ip_documentation/axi_spi/v1_02_a/axi_spi_ds742.pdf
Table 1 - page 4

Checking through the hw design every pin is connected to device to do chip select.
That's why I think that num-cs (based on spi-bus.txt) is the right property.

Of course hw guys can use decoder from these bits and we could use binding
as is used in cadence spi (is-decoded-cs)

> I'm not convinced num-cs ever made any sense.

Does it mean that num-cs property used by 11 SPI drivers is just incorrect?

Based on Documentation/devicetree/bindings/spi/spi-bus.txt it is the part of binding
- num-cs : total number of chipselects

Please let me know what you think.

Thanks,
Michal



  reply	other threads:[~2015-03-27 10:56 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-16 12:55 Michal Simek
2015-02-12  9:45 ` Michal Simek
     [not found] ` <CAHTX3dJRGhwo7FW+VJxfEJmx-9FdjFN5EnxG0RRDfMOm3=VU4A@mail.gmail.com>
2015-02-14  5:35   ` Mark Brown
2015-02-23 10:22     ` Michal Simek
2015-02-24 14:52       ` Mark Brown
2015-03-08 19:00 ` Mark Brown
2015-03-27 10:55   ` Michal Simek [this message]
2015-03-27 17:53     ` Mark Brown
2015-03-30  6:46       ` Michal Simek
2015-03-31  5:47         ` Mark Brown
2015-03-31  8:16           ` Michal Simek
2015-03-31 11:16             ` Mark Brown
2015-03-31 11:25               ` Michal Simek
2015-03-31 12:24                 ` Mark Brown

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