Re: [PATCH 1/3] ARM: omap_device: handle first time activation of console device

Rajendra Nayak
2011-11-17T07:19:11Z

[...]
>> +static int omap_console_hwmod_enable(struct omap_device *od)
>> +{
>> + console_lock();
>> + /*
>> + * For early console we prevented hwmod reset and idle
>
> A period is missing. Or maybe it should a comma with not capital letter.
>
>> + * So before we enable the uart clocks idle the console
>> + * uart clocks, then enable back the console uart hwmod.
>> + */
>> + omap_hwmod_idle(od->hwmods[0]);
>> + omap_hwmod_enable(od->hwmods[0]);
>
> Why do we have to idle -> enable? The module is already enabled, isn't it?
> The comment is not super clear for me :-)
> Is the goal is to reset the IP?

Yes, now that I read it, it does sound confusing. I should have at-least
read it once before I picked it from serial.c

But anyway, here's what the problem is.

I feel its partly to do with the inability of hwmod to handle some
modules which are left enabled post a setup, due to the
'HWMOD_INIT_NO_IDLE' flag set.
Such modules end up with a hwmod state as '_HWMOD_STATE_ENABLED' post
a setup. Now when a driver for such devices/modules tries to enable the
module the first time, hwmod throws up a big WARN stating the hwmod is
already in an enabled state.
[uart used as console is one such module, which cannot be idled post a
setup by hwmod]

If hwmod could be made in some way intelligent enough to know that the
module is in enabled state because of the 'HWMOD_INIT_NO_IDLE' itself,
a lot of this hackery might not be needed at all.
Simplest way to do it could be to just add another intermediate state,
something like '_HWMOD_STATE_ENABLED_AT_INIT'.
I will post a patch for this, see if you like it being handled that way.

The other part of the problem is also with the inability to hook up
'custom' omap_device_pm_latency for omap devices created from DT.
Maybe a lot of such cases which need custom activate/deactivate
functions might have to be handled in some way in the framework
itself like the one above.