linux-kernel - Re: [PATCH 4/4] wl1251: spi: add device tree support

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Date:	Mon, 28 Oct 2013 14:30:45 -0500
From:	Kumar Gala <galak@...eaurora.org>
To:	Grazvydas Ignotas <notasas@...il.com>
Cc:	Sebastian Reichel <sre@...ian.org>,
	Mark Rutland <mark.rutland@....com>, linux-doc@...r.kernel.org,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Sebastian Reichel <sre@...g0.de>,
	Luciano Coelho <luca@...lho.fi>, devicetree@...r.kernel.org,
	Pawel Moll <pawel.moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	"John W. Linville" <linville@...driver.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Bill Pemberton <wfp5p@...ginia.edu>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Felipe Balbi <balbi@...com>, Rob Landley <rob@...dley.net>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 4/4] wl1251: spi: add device tree support


On Oct 28, 2013, at 12:15 PM, Grazvydas Ignotas wrote:

> On Mon, Oct 28, 2013 at 8:37 AM, Kumar Gala <galak@...eaurora.org> wrote:
>> On Oct 27, 2013, at 11:14 AM, Sebastian Reichel wrote:
>>> +++ b/Documentation/devicetree/bindings/net/wireless/ti,wl1251.txt
>>> @@ -0,0 +1,36 @@
>>> +* Texas Instruments wl1251 controller
>>> +
>>> +The wl1251 chip can be connected via SPI or via SDIO. The linux
>>> +kernel currently only supports device tree for the SPI variant.
>>> +
>> 
>> From the binding I have no idea what this chip actually does, also we don't normally reference linux kernel support in bindings specs (so please remove it).
>> 
>> However, what would expect the SDIO binding to look like?  Or more specifically, how would you distinguish the SPI vs SDIO binding/connection?  I'm wondering if the compatible should be something like "ti,wl1251-spi" and than the sdio can be "ti,wl1251-sdio"
> 
> When connected to SDIO, it doesn't act as standard SDIO device and
> can't be probed (standard SDIO registers missing), so information has
> to come some other way. That used to partially come through
> platform_data and partially through a callback from mmc subsystem (see
> pandora_wl1251_init_card() in
> arch/arm/mach-omap2/board-omap3pandora.c). I don't know much about DT,
> but maybe the information that comes from SDIO registers on "normal"
> SDIO devices should come through DT in this case too? I don't really
> know how that should be integrated with mmc subsystem though..

Ok, my point is still valid that we can use a different compatible for the SDIO case even if its no standard SDIO vs the SPI case.

> 
>>> +Required properties:
>>> +- compatible : Should be "ti,wl1251"
>> 
>> reg is not listed as a required prop.
>> 
>>> +- interrupts : Should contain interrupt line
>>> +- interrupt-parent : Should be the phandle for the interrupt
>>> +  controller that services interrupts for this device
>>> +- vio-supply : phandle to regulator providing VIO
>>> +- power-gpio : GPIO connected to chip's PMEN pin
>> 
>> should be vendor prefixed: ti,power-gpio
>> 
>>> +- For additional required properties on SPI, please consult
>>> +  Documentation/devicetree/bindings/spi/spi-bus.txt
>>> +
>>> +Optional properties:
>>> +- ti,use-eeprom : If found, configuration will be loaded from eeprom.
>> 
>> can you be a bit more specific on what cfg will be loaded.  Also, is this property a boolean, if so how do I know which eeprom the cfg is loaded from (is it one that is directly connected to the wl1251?
> 
> wl1251 is a wifi chip that can have an optional eeprom connected to it
> to store things like calibration stuff and MAC address, and that
> eeprom is usually inside a single module with some additional radio
> related chips. If the eeprom is connected (like the module on pandora
> board has), the driver can issue command to the firmware running on
> chip to load that data on it's startup, alternatively the driver can
> load calibration from other storage (like it happens on N900).

So sounds like a boolean.  I think just adding that its a boolean and maybe something like "configuration (calibration data, MAC addr, etc..)"

- k

> 
> 
> Gražvydas
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