Re: [PATCH v2 2/3] clk: ti: check clock type before doing autoidle ops

From: Tony Lindgren <tony@atomide.com>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>,
	Andreas Kemnade <andreas@kemnade.info>,
	bcousson@baylibre.com, letux-kernel@openphoenux.org,
	linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-omap@vger.kernel.org, mturquette@baylibre.com,
	paul@pwsan.com
Subject: Re: [PATCH v2 2/3] clk: ti: check clock type before doing autoidle ops
Date: Mon, 3 Dec 2018 07:39:10 -0800	[thread overview]
Message-ID: <20181203153910.GA6707@atomide.com> (raw)
In-Reply-To: <154362191595.88331.15503578806026771935@swboyd.mtv.corp.google.com>

* Stephen Boyd <sboyd@kernel.org> [181130 23:52]:
> Quoting Tony Lindgren (2018-11-30 07:37:29)
> > Hi,
> > 
> > * Tero Kristo <t-kristo@ti.com> [181130 09:21]:
> > > On 30/11/2018 09:57, Stephen Boyd wrote:
> > > > No that is not preferred. Can the omap2_clk_deny_idle() function be
> > > > integrated closer into the clk framework in some way that allows it to
> > > > be part of the clk_ops structure? And then have that take a clk_hw
> > > > structure instead of a struct clk? I haven't looked at this in any
> > > > detail whatsoever so I may be way off right now.
> > > 
> > > It could be added under the main clk_ops struct, however this would
> > > introduce two new func pointers to it which are not used by anything else
> > > but OMAP. Are you aware of any other platforms requiring similar feature?
> > 
> > From consumer usage point of view, I'm still wondering about
> > the relationship of clk_deny_idle() and clkdm_deny_idle().
> > 
> > It seems that we need to allow reset control drivers call
> > clk_deny_idle() for the duration of reset. And it seems the
> > clk_deny_idle() should propagate to also up to the related
> > clock domain driver to do clkdm_deny_idle().
> > 
> > So maybe clk_deny_idle() is could just be something like:
> > 
> > dev = clk_get_device(clk);
> > ...
> > error = pm_runtime_get(dev);
> > ...
> > pm_runtime_put(dev);
> > ...
> > 
> > And that way it would just propagate to the parent clock
> > domain driver and the clock framework does not need to know
> > about clockdomains. A clockdomain could be just a genpd
> > domain.
> > 
> > Or do you guys have better ideas?
> > 
> 
> Wouldn't the device link in clk framework patches do this for you if we
> had the RUNTIME_PM flag passed in. If this is about keeping the clock
> controller active when a consumer device is using it then I think it may
> work.

The consumer device stays active just fine with PM runtime
calls. So yes, the problem is keeping a clock controller forced
active for the period of consumer device reset. Other than
that typically autoidle can be just kept enabled.

Below is a clarified suggested example usage if we wanted to
use PM runtime on a clock controller device from a consumer
device reset driver:

error = pm_runtime_get_dev()
...
cdev = clk_get_device(clk);
...
error = pm_runtime_get(cdev);
...
/* Do the consumer device reset here */
...
pm_runtime_put(cdev);
pm_runtime_put(dev);

Regards,

Tony