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

Tomi Valkeinen tomi.valkeinen at ti.com
Wed Jun 27 00:19:58 EDT 2012

On Tue, 2012-06-26 at 17:47 -0700, Mike Turquette wrote:
> 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.

That's not quite what I meant. If it's the driver that does clk_enable,
be it in runtime PM callback or not, it's driver's responsibility.

But some clocks are not handled by the driver, but the hwmod/omap_device
framework. Mainly I think this is for the functional and interface
clocks. The driver has no visibility to those, they are implicitly
enabled via pm_runtime_get.


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