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

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Date:	Mon, 2 Feb 2015 08:59:57 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	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 Sun, Feb 1, 2015 at 11:18 PM, Mike Turquette <mturquette@...aro.org> wrote:
> Quoting Tomeu Vizoso (2015-01-31 10:36:22)
>> On 31 January 2015 at 02:31, Stephen Boyd <sboyd@...eaurora.org> wrote:
>> > 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.
>>
>> Hi, this looks good to me.
>>
>> Reviewed-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>
> It seems to fix the total boot failure on OMAPs, and hopefully does the
> same for SH Mobile and others. I've squashed this into Tomeu's rate
> constraints patch to maintain bisect.

Yes, it fixes shmobile. .round_rate() is now called with a sane value of rate.

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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