Re: [PATCH] i2c-designware: add OF binding support

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Ben,

On 08/04/2011 04:12 AM, Ben Dooks wrote:
> On Wed, Aug 03, 2011 at 03:04:23PM -0500, Rob Herring wrote:
>> From: Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
>>
>> Add of_match_table and DT style i2c registration to designware i2c
>> driver.
>>
>> Signed-off-by: Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
>> Cc: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
>> Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
>> Cc: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
>> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>> ---
>>  Documentation/devicetree/bindings/i2c/dw-i2c.txt |   23 ++++++++++++++++++++++
>>  drivers/i2c/busses/i2c-designware.c              |   13 ++++++++++++
>>  2 files changed, 36 insertions(+), 0 deletions(-)
>>  create mode 100644 Documentation/devicetree/bindings/i2c/dw-i2c.txt
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/dw-i2c.txt b/Documentation/devicetree/bindings/i2c/dw-i2c.txt
>> new file mode 100644
>> index 0000000..cbcb404
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/dw-i2c.txt
>> @@ -0,0 +1,23 @@
>> +* Synopsys DesignWare I2C
>> +
>> +Required properties :
>> +
>> + - compatible : should be "snps,designware-i2c"
>> + - reg : Offset and length of the register set for the device
>> + - interrupts : <IRQ> where IRQ is the interrupt number.
>> +
>> +Recommended properties :
>> +
>> + - clock-frequency : desired I2C bus clock frequency in Hz.
>> +
>> +Example :
>> +
>> +	i2c@f0000 {
>> +		#address-cells = <1>;
>> +		#size-cells = <0>;
>> +		compatible = "snps,designware-i2c";
>> +		reg = <0xf0000 0x1000>;
>> +		interrupts = <11>;
>> +		clock-frequency = <400000>;
>> +	};
>> +
> 
> looks good to me.
> 
>> diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c
>> index b7a51c4..2911a49 100644
>> --- a/drivers/i2c/busses/i2c-designware.c
>> +++ b/drivers/i2c/busses/i2c-designware.c
>> @@ -37,6 +37,7 @@
>>  #include <linux/platform_device.h>
>>  #include <linux/io.h>
>>  #include <linux/slab.h>
>> +#include <linux/of_i2c.h>
>>  
>>  /*
>>   * Registers offset
>> @@ -770,12 +771,17 @@ static int __devinit dw_i2c_probe(struct platform_device *pdev)
>>  	adap->algo = &i2c_dw_algo;
>>  	adap->dev.parent = &pdev->dev;
>>  
>> +#ifdef CONFIG_OF
>> +	r = i2c_add_adapter(adap);
>> +#else
>>  	adap->nr = pdev->id;
>>  	r = i2c_add_numbered_adapter(adap);
>> +#endif
> 
> I would say that doing the #ifdef CONFIG_OF is dangerous here when we
> are in a mixed OF/platform enviromnent as we're depending on compile
> time selection.
> 
> I'm also wondering whether we have an of helper macro which takes
> a pdev and gives you an adapter number either given on pdev->id or
> -1 for the case when we're using the OF bindings.
> 
> It might be worth talking to Grant about setting pdev->id to -1 if we
> are using an OF device.
> 

As Grant said, that's already done and this hunk is not needed.

>>  	if (r) {
>>  		dev_err(&pdev->dev, "failure adding adapter\n");
>>  		goto err_free_irq;
>>  	}
>> +	of_i2c_register_devices(adap);
> 
> If we did that, we could add a of_i2c_register_adapter() call which
> would take the platform device and then do the of_i2c_register_devices()
> and do these steps.
> 

Better yet, how about putting of_i2c_register_devices into
i2c_register_adapter? Everywhere that calls of_i2c_register_devices is
preceded by a call to i2c_add_numbered_adapter or i2c_add_adapter. It
seems logical to put it with i2c_scan_static_board_info. I'll prepare a
patch to add that and remove all the other callers unless you think
that's a bad idea.

>>  	return 0;
>>  
>> @@ -819,6 +825,12 @@ static int __devexit dw_i2c_remove(struct platform_device *pdev)
>>  	return 0;
>>  }
>>  
>> +static const struct of_device_id dw_i2c_of_match[] = {
>> +	{ .compatible = "snps,designware-i2c", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, dw_i2c_of_match);
>> +
>>  /* work with hotplug and coldplug */
>>  MODULE_ALIAS("platform:i2c_designware");
>>  
>> @@ -827,6 +839,7 @@ static struct platform_driver dw_i2c_driver = {
>>  	.driver		= {
>>  		.name	= "i2c_designware",
>>  		.owner	= THIS_MODULE,
>> +		.of_match_table = dw_i2c_of_match,
> 
> If my patch for of_match_ptr() is accepted, it will be needed here
> otherwise you will need to do something about remvoing the of table
> above if not config of.

There's really not much harm with having the table. If you match the
device in the non-DT way, the table is not used. Drivers should never
directly access the table either, but use the helpers to get their data.

Rob