Re: [RFC/NOT FOR MERGING 2/3] serial: omap: remove hwmod dependency

[Santosh Shilimkar <santosh.shilimkar@ti.com>]

On Friday 15 February 2013 10:12 PM, Felipe Balbi wrote:
> Hi,
>
> On Fri, Feb 15, 2013 at 08:30:32AM -0800, Tony Lindgren wrote:
>> * Santosh Shilimkar <santosh.shilimkar@ti.com> [130215 05:34]:
>>> On Friday 15 February 2013 06:57 PM, Russell King - ARM Linux wrote:
>>>> On Fri, Feb 15, 2013 at 06:56:47PM +0530, Santosh Shilimkar wrote:
>>>>> Whats your view on use of arch_ioremap_caller() hook ? This can allow
>>>>> us to avoid the dual ioremap() issue discussed here if the hook
>>>>> maintains the list of mapped ios.
>>>>>
>>>>> I was even thinking of having such intelligence within the core
>>>>> ioremap code but thought that might be too invasive.
>>>>
>>>> Why do you even need it?  There's no problem with ioremapping the same
>>>> space multiple times (you end up with multiple mappings but that
>>>> shouldn't be a problem, except for the additional space used.)
>>>>
>>> It just waste of iospace and Tony insisted to have just single ioremap()
>>> hence all this discussion
>>
>> The main goal is to avoid duplicating data both in hwmod and DT.
>> That's pretty much solved as we can have the driver probe populate
>> the common data for hwmod from DT as Santosh has already demonstrated.
>>
>> Then we also want the driver specific idle and reset code to be done
>> in the drivers rather than in hwmod and glue it together with hwmod
>> using runtime PM. The biggest issue there is how do we reset and idle
>> some piece of hardware for PM purposes when there's no driver loaded.
>
> right, this will be a tough nut to crack.
>
> I guess the only way would be reset all IPs early in the boot process,
> before even creating the platform-devices. Can we do that ? I mean, from
> omap_device_build_from_dt() we have access to address space of all
> devices, through ti,hwmods we can figure out which hwmods are linked to
> that particular device, so whenever you build a device, you could just
> call _reset().
>
Thats what we do today and it works perfectly. As per Tony's suggestion,
we need to move the non-probed devices reset and idle setup to late_init
which is also doable.

In that case when probed driver calls runtime_get(), we reset that
device and setup the idle settings. And remainder of the devices
are managed in late_init().

> The only problem is that now omap_device_build_from_dt() is called after
> we notify that a new device/driver pair has been registered with the
> platform_bus, right ? So we would still need a way to call _reset() for
> those which are on DTS but don't have a driver bound to them...
>
The only special requirement for reset remains(which today handled by
hwmod function calls) is for devices which needs specific reset
sequence. And this one can be handled through a runtime_reset()
kind of hook.

Does that sound reasonable ?

Regards,
Santosh