linux-kernel - Re: [PATCHv9 03/18] TEMP: OMAP3xxx: hwmod data: add PRM hwmod

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Date:	Thu, 20 Oct 2011 16:51:14 +0200
From:	"Cousson, Benoit" <b-cousson@...com>
To:	Paul Walmsley <paul@...an.com>
CC:	"Kristo, Tero" <t-kristo@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv9 03/18] TEMP: OMAP3xxx: hwmod data: add PRM hwmod

On 10/13/2011 6:51 PM, Paul Walmsley wrote:
> On Thu, 13 Oct 2011, Paul Walmsley wrote:
>
>> On Wed, 12 Oct 2011, Cousson, Benoit wrote:
>>
>>> On 10/11/2011 1:26 AM, Paul Walmsley wrote:
>>>> On Tue, 11 Oct 2011, Cousson, Benoit wrote:
>>>>
>>>>> In fact the device name does not have to match the hwmod name. So we
>>>>> can just create an "omap2_prm" omap_device for OMAP2, "omap3_prm"
>>>>> omap_device for OMAP3... That will allow the relevant PRM driver to
>>>>> be bound to the proper device.
>>>>
>>>> Incidentally, given that we would be using the hwmod name and the version
>>>> number to determine the appropriate omap_device name, what IP version
>>>> numbers should we assign to these PRM IP blocks for different SoCs?
>>>
>>> It can just be 1, 2 and 3... The idea is just to differentiate the IP for each
>>> OMAP.
>>
>> So those are basically arbitrary?  Something is not clear here.
>>
>> In the current hwmod design, IP blocks with different interfaces were
>> intended to be uniquely identified by the hwmod name alone.  That is why
>> omap_hwmod_lookup() only takes a 'name' parameter.
>>
>> If I understand what you want to do, you wish to change this to uniquely
>> identify them by a (name, interface version number) tuple.
>>
>> I don't have a problem with this in theory, but it implies some changes to
>> the existing model.  Specifically:
>>
>> - we'll need to add an interface version number to the struct omap_hwmod
>>
>> - we'll need to modify omap_hwmod_lookup() to take an interface version
>> number
>>
>> - the "ti,hwmod" DT binding that you proposed earlier will need to include
>> an interface version number
>
> Hmm, reflecting on this further, is your intention to bind drivers to
> hwmods by the struct omap_hwmod_class instead?

Well, somehow, the class was added for that purpose, to allow one timer 
driver to bind to 2 different hwmods. But in that case the device name 
was the same.

> If we define that "rev" field as the interface version number, that should
> probably work.
>
> So then in C struct format, in a platform_device system, the mapping table
> would basically become
>
> struct omap_hwmod_driver_map {
> 	const char *class_name;
> 	const u32 class_rev;
> 	const char *platform_device_name;
> }

This is needed if and only if you want to have a different driver for 
the same IP.

In the case of the timer, we do have only one device name and one driver:
class=timer, rev=1, device=omap_timer
class=timer, rev=2, device=omap_timer

Regards,
Benoit
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