linux-kernel - Re: [PATCH v13 4/6] clk: Add rate constraints to clocks

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Date:	Fri, 30 Jan 2015 17:31:58 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Mike Turquette <mturquette@...aro.org>
Cc:	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	Chao Xie <chao.xie@...vell.com>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Corbet <corbet@....net>,
	Emilio L??pez <emilio@...pez.com.ar>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	Alex Elder <elder@...aro.org>,
	Zhangfei Gao <zhangfei.gao@...aro.org>,
	Bintian Wang <bintian.wang@...wei.com>,
	Matt Porter <mporter@...aro.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Tero Kristo <t-kristo@...com>,
	Manuel Lauss <manuel.lauss@...il.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Subject: Re: [PATCH v13 4/6] clk: Add rate constraints to clocks

On 01/29, Stephen Boyd wrote:
> On 01/29/15 05:31, Geert Uytterhoeven wrote:
> > Hi Tomeu, Mike,
> >
> > On Fri, Jan 23, 2015 at 12:03 PM, Tomeu Vizoso
> > <tomeu.vizoso@...labora.com> wrote:
> >> --- a/drivers/clk/clk.c
> >> +++ b/drivers/clk/clk.c
> >> @@ -2391,25 +2543,24 @@ int __clk_get(struct clk *clk)
> >>         return 1;
> >>  }
> >>
> >> -static void clk_core_put(struct clk_core *core)
> >> +void __clk_put(struct clk *clk)
> >>  {
> >>         struct module *owner;
> >>
> >> -       owner = core->owner;
> >> +       if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
> >> +               return;
> >>
> >>         clk_prepare_lock();
> >> -       kref_put(&core->ref, __clk_release);
> >> +
> >> +       hlist_del(&clk->child_node);
> >> +       clk_core_set_rate_nolock(clk->core, clk->core->req_rate);
> > At this point, clk->core->req_rate is still zero, causing
> > cpg_div6_clock_round_rate() to be called with a zero "rate" parameter,
> > e.g. on r8a7791:
> 
> Hmm.. I wonder if we should assign core->req_rate to be the same as
> core->rate during __clk_init()? That would make this call to
> clk_core_set_rate_nolock() a nop in this case.
> 

Here's a patch to do this

---8<----
From: Stephen Boyd <sboyd@...eaurora.org>
Subject: [PATCH] clk: Assign a requested rate by default

We need to assign a requested rate here so that we avoid
requesting a rate of 0 on clocks when we remove clock consumers.

Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 drivers/clk/clk.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a29daf9edea4..8416ed1c40be 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2142,6 +2142,7 @@ int __clk_init(struct device *dev, struct clk *clk_user)
 	struct clk_core *orphan;
 	struct hlist_node *tmp2;
 	struct clk_core *clk;
+	unsigned long rate;
 
 	if (!clk_user)
 		return -EINVAL;
@@ -2266,12 +2267,13 @@ int __clk_init(struct device *dev, struct clk *clk_user)
 	 * then rate is set to zero.
 	 */
 	if (clk->ops->recalc_rate)
-		clk->rate = clk->ops->recalc_rate(clk->hw,
+		rate = clk->ops->recalc_rate(clk->hw,
 				clk_core_get_rate_nolock(clk->parent));
 	else if (clk->parent)
-		clk->rate = clk->parent->rate;
+		rate = clk->parent->rate;
 	else
-		clk->rate = 0;
+		rate = 0;
+	clk->rate = clk->req_rate = rate;
 
 	/*
 	 * walk the list of orphan clocks and reparent any that are children of
-- 
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a Linux Foundation Collaborative Project
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