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

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Message-ID: <20140630203225.GA3893@amd.pavel.ucw.cz>
Date:	Mon, 30 Jun 2014 22:32:25 +0200
From:	Pavel Machek <pavel@....cz>
To:	Suman Anna <s-anna@...com>
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!

> >>>> 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

Aha, ok, then the intr_type should be derived from
compatible-string. Or rather... you should have three
compatible-strings for the three possibilities? (And then subtype,
currently unused, in case there are more hw differences).

> 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.

Ok, right... I'd vote for putting them into DT.

								Pavel
-- 
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