linux-kernel - Re: [PATCH-v5 RESEND 3/5] i2c: pxa: Add support for pxa910/988 & new configuration features

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Date:	Mon, 14 Sep 2015 10:58:23 +0530
From:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-arm-kernel@...ts.infradead.org, robh+dt@...nel.org,
	robert.jarzmik@...e.fr, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	"Jett.Zhou" <jtzhou@...vell.com>, Yi Zhang <yizhang@...vell.com>
Subject: Re: [PATCH-v5 RESEND 3/5] i2c: pxa: Add support for pxa910/988 & new
 configuration features



On Saturday 12 September 2015 12:36 AM, Wolfram Sang wrote:
> On Mon, Aug 24, 2015 at 11:29:36AM +0530, Vaibhav Hiremath wrote:
>> TWSI_ILCR & TWSI_IWCR registers are used to adjust clock rate
>> of standard & fast mode in pxa910/988; so this patch adds these two new
>> entries to "struct pxa_reg_layout" and "struct pxa_i2c".
>>
>> As discussed in the previous patch-series, the idea here is to add standard
>> DT properties for ilcr and iwcr configuration fields.
>> In case of Master ilcr is used for low/high time and in case of slave mode
>> of operation iwcr is used for setup/hold time.
>
> I need to rethink how to describe i2c bus timing parameters in DT in the
> next days. But this is planned for 4.4., promised.
>
> One thing I already wonder about this one...
>
>>   static const struct platform_device_id i2c_pxa_id_table[] = {
>>   	{ "pxa2xx-i2c",		REGS_PXA2XX },
>>   	{ "pxa3xx-pwri2c",	REGS_PXA3XX },
>>   	{ "ce4100-i2c",		REGS_CE4100 },
>> +	{ "pxa910-i2c",		REGS_PXA910 },
>>   	{ },
>
> You add a new platform_id...
>
>> @@ -1135,7 +1170,7 @@ static const struct i2c_algorithm i2c_pxa_pio_algorithm = {
>>   static const struct of_device_id i2c_pxa_dt_ids[] = {
>>   	{ .compatible = "mrvl,pxa-i2c", .data = (void *)REGS_PXA2XX },
>>   	{ .compatible = "mrvl,pwri2c", .data = (void *)REGS_PXA3XX },
>> -	{ .compatible = "mrvl,mmp-twsi", .data = (void *)REGS_PXA2XX },
>> +	{ .compatible = "mrvl,mmp-twsi", .data = (void *)REGS_PXA910 },
>>   	{}
>
> ...but change the compatible binding instead of adding a new one?
>

Yes, because the offset for both REGS_PXA2XX and REGS_PXA910 are same,
and for REGS_PXA2XX we already have compatible entry "mrvl,pxa-i2c".
And the i2c binding documentation, which says,
for platforms using REGS_PXA2XX, they need to provide additional node
"mrvl,pxa-i2c". Which is confusing :)

Also, when I did git-blame on the driver file to see why "mmp-twsi"
entry has been added without anyone really using it. But I did not find
anything meaningful.
So, from the code it was very clear that, "mmp-twsi" and "pxa-i2c" both
are same, its the code which I am adding here brings difference between 
them.

I tried to find datasheet for the platforms using "mmp-twsi", but was
unlucky.


Thanks,
Vaibhav




Thanks,
Vaibhav
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