Subject: [PATCH 05/11] OMAPDSS: add clk_prepare and clk_unprepare

From: [email-masked] (Mike Turquette)
Date: Tue, 26 Jun 2012 17:47:10 -0700

On 20120625-16:14, Tomi Valkeinen wrote:
> A question about clk_prepare/unprepare, not directly related: let's say
> I have a driver for some HW block. The driver doesn't use clk functions,
> but uses runtime PM. The driver also sets pm_runtime_irq_safe().
> 
> Now, the driver can call pm_runtime_get_sync() in an atomic context, and
> this would lead to the underlying framework (hwmod, omap_device, I don't
> know who =) enabling the func clock for that HW. But this would happen
> in atomic context, so the underlying framework can't use clk_prepare.
> 
> How does the underlying framework handle that case? (sorry if that's a
> stupid question =).
> 

I think it's a good question!

If we're going to call clk_prepare_enable from within a runtime pm
callback then I think we'll need to check if _irq_safe() is set and
conditionally call only clk_enable in such a case.

I'm not a runtime pm expert, but if the driver owns the responsibility
of calling pm_runtime_irq_safe then the driver has the proper context
to know that it should call clk_prepare BEFORE calling
pm_runtime_get_sync.

However if some other framework (outside of the driver) calls
pm_runtime_irq_safe then it will be difficult for the driver to know
what to do...

Regards,
Mike

>  Tomi