linux-kernel - Re: [PATCH v3 2/2] i2c: i2c-ocores: Add support for the GRLIB port of the controller and custom getreg and setreg functions

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Message-ID: <87sj8d86lo.fsf@dell.be.48ers.dk>
Date:	Tue, 13 Nov 2012 23:45:39 +0100
From:	Peter Korsgaard <jacmet@...site.dk>
To:	Andreas Larsson <andreas@...sler.com>
Cc:	Wolfram Sang <w.sang@...gutronix.de>,
	Ben Dooks <ben-linux@...ff.org>, linux-i2c@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	software@...sler.com
Subject: Re: [PATCH v3 2/2] i2c: i2c-ocores: Add support for the GRLIB port of the controller and custom getreg and setreg functions

>>>>> "Andreas" == Andreas Larsson <andreas@...sler.com> writes:

Hi,

 Andreas> The registers in the GRLIB port of the controller are 32-bit
 Andreas> and in big endian byte order. The PRELOW and PREHIGH registers
 Andreas> are merged into one register. The subsequent registers have
 Andreas> their offset decreased accordingly. Hence the register access
 Andreas> needs to be handled in a non-standard manner using custom
 Andreas> getreg and setreg functions.

 Andreas> @@ -257,6 +300,14 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,

 Andreas>  	of_property_read_u32(pdev->dev.of_node, "reg-io-width",
 Andreas>  				&i2c->reg_io_width);
 Andreas> +
 Andreas> +	if (of_device_is_compatible(pdev->dev.of_node,
 Andreas> +				    "aeroflexgaisler,i2cmst")) {
 Andreas> +		dev_dbg(&pdev->dev, "GRLIB variant of i2c-ocores\n");
 Andreas> +		i2c->setreg = oc_setreg_grlib;
 Andreas> +		i2c->getreg = oc_getreg_grlib;
 Andreas> +	}
 Andreas> +

Please also update the bindings documentation under
Documentation/devicetree/bindings/i2c.

With this core you need to add both aeroflexgaisler,i2cmst and
opencores,i2c-ocores to the compatible property, but the grlib variant
is NOT compatible with i2c-ocores, so that's not really nice.

Adding a type define (TYPE_OCORES / TYPE_GRLIB) and a 2nd of_device_id
entry with .data = TYPE_GRLIB, and then using that in the probe routine
would be nicer. Have a look at i2c-at91.c for an example of a driver
doing something like that.

-- 
Bye, Peter Korsgaard
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