linux-kernel - Re: [PATCHv2] wlcore: spi: add wl18xx support

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Date:	Mon, 18 Apr 2016 00:19:41 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Reizer, Eyal" <eyalr@...com>
Cc:	Kalle Valo <kvalo@...eaurora.org>,
	Eyal Reizer <eyalreizer@...il.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-spi@...r.kernel.org
Subject: Re: [PATCHv2] wlcore: spi: add wl18xx support

On Sunday 10 April 2016 07:37:23 Reizer, Eyal wrote:
> Add support for using with both wl12xx and wl18xx.
> 
> - all wilink family needs special init command for entering wspi mode.
>   extra clock cycles should be sent after the spi init command while the
>   cs pin is high.
> - switch to controling the cs pin from the spi driver for achieveing the
>   above.
> - the selected cs gpio is read from the spi device-tree node using the
>   cs-gpios field and setup as a gpio.
> - See the example below for specifying the cs gpio using the cs-gpios entry
> &spi0   {
>         ...
>         cs-gpios = <&gpio0 5 0>;
>         ...
>         wlcore: wlcore@0 {
>                 compatible = "ti,wl1835";
>         ...
>         ...
>         };
> };
> 
> Signed-off-by: Eyal Reizer <eyalr@...com>

I don't think this can work in general: not all SPI hosts uses GPIOs
for controlling CS, so the logic can't work, and it's also a layering
violation for the driver to look at the parent.

I would suggest fixing this using a new API function from the SPI
core, if we don't already have a generic way to do it.

	Arnd