linux-kernel - Re: [PATCH 2/6] mailbox/omap: add support for parsing dt devices

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Message-ID: <53B1BBA8.5090507@ti.com>
Date:	Mon, 30 Jun 2014 14:34:00 -0500
From:	Suman Anna <s-anna@...com>
To:	Pavel Machek <pavel@....cz>
CC:	Tony Lindgren <tony@...mide.com>,
	Jassi Brar <jaswinder.singh@...aro.org>,
	Dave Gerlach <d-gerlach@...com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH 2/6] mailbox/omap: add support for parsing dt devices

Hi Pavel,

>
>>>> The non-DT support has to be maintained for now to not break
>>>> OMAP3 legacy boot, and the legacy-style code will be cleaned
>>>> up once OMAP3 is also converted to DT-boot only.
>>>
>>>> @@ -587,24 +606,157 @@ static int omap_mbox_unregister(struct omap_mbox_device *mdev)
>>>>  	return 0;
>>>>  }
>>>>  
>>>> +static const struct omap_mbox_device_data omap2_data = {
>>>> +	.num_users	= 4,
>>>> +	.num_fifos	= 6,
>>>> +	.intr_type	= MBOX_INTR_CFG_TYPE1,
>>>> +};
>>>> +
>>>> +static const struct omap_mbox_device_data omap3_data = {
>>>> +	.num_users	= 2,
>>>> +	.num_fifos	= 2,
>>>> +	.intr_type	= MBOX_INTR_CFG_TYPE1,
>>>> +};
>>>> +
>>>> +static const struct omap_mbox_device_data am335x_data = {
>>>> +	.num_users	= 4,
>>>> +	.num_fifos	= 8,
>>>> +	.intr_type	= MBOX_INTR_CFG_TYPE2,
>>>> +};
>>>
>>> So you use compatible strings to look up 3 integers. Would it be better to have
>>> num_users/num_fifos/intr_type directly in the device tree? That should be cleaner
>>> and more flexible...
>>>
>>> If you do that, would it be possible to have share compatible string?
>>
>> Yeah, I have actually encoded the .num_users and .num_fifos in DT in the
>> previous version [1] with shared compatible strings, but dropped those
>> properties in favour of adding minimal custom properties to DT based on
>> some offline IRC comments. I have no objections either way, but there is
>> really nothing to be gained from minimizing compatible strings.
> 
> Actually, I'd guess best solution would be to do both: have it encoded
> in device tree _and_ have separate compatible string for each version
> (in case there are other differences). You'd still get rid of the
> table...

Do note that the .intr_type has to with the register layout rather than
a physical property (mainly to distinguish the pre-OMAP4 IP register
layout), so I am not convinced that belongs to DT. This is the reason
why I didn't represent it in DT even in the previous version. The other
two are HW IP design parameters, so in general putting them in DT isn't
completely a bad idea, but I will wait to see if there are any further
comments on this from Tony or DT maintainers before I make changes.

regards
Suman
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