linux-kernel - Re: [PATCH 2/6] clk: tegra: make tegra_clocks_apply_init_table arch

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Date:	Mon, 21 Jul 2014 23:55:25 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Peter De Schrijver <pdeschrijver@...dia.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	Joseph Lo <josephl@...dia.com>,
	Alex Courbot <acourbot@...dia.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Tuomas Tynkkynen <ttynkkynen@...dia.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/6] clk: tegra: make tegra_clocks_apply_init_table
 arch_initcall

On Mon, Jul 21, 2014 at 03:43:08PM -0600, Stephen Warren wrote:
> On 07/16/2014 02:27 AM, Peter De Schrijver wrote:
> > On Wed, Jul 16, 2014 at 09:19:33AM +0200, Thierry Reding wrote:
> >> * PGP Signed by an unknown key
> >>
> >> On Tue, Jul 15, 2014 at 06:24:32PM +0300, Peter De Schrijver wrote:
> >> [...]
> >>> diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c
> >>> index d081732..65cde4e 100644
> >>> --- a/drivers/clk/tegra/clk.c
> >>> +++ b/drivers/clk/tegra/clk.c
> >>> @@ -290,10 +290,13 @@ struct clk ** __init tegra_lookup_dt_id(int clk_id,
> >>>  
> >>>  tegra_clk_apply_init_table_func tegra_clk_apply_init_table;
> >>>  
> >>> -void __init tegra_clocks_apply_init_table(void)
> >>> +static int __init tegra_clocks_apply_init_table(void)
> >>>  {
> >>>  	if (!tegra_clk_apply_init_table)
> >>> -		return;
> >>> +		return 0;
> >>
> >> Shouldn't this be an error? Or perhaps WARN()? To make sure this gets
> > 
> > An arch_initcall will be called for every ARM platform I think? In case
> > this gets called on a non-Tegra platform, tegra_clk_apply_init_table will not
> > be set and therefore a silent return 0; seems the most appropriate thing to do
> > to me?
> 
> This is one reason that doing all the initialization from separate
> initcalls sucks. Much better to have a single top-level initialization
> function that calls exactly what is needed, only what is needed, and
> only runs on the correct SoCs.
> 
> But failing that, I guess you need to say something like
> of_is_compatible(root node, "nvidia Tegra"), but of course the
> definition of "nvidia Tegra" is an ever-growing list of possible values
> that needs to be used from each separate initcall...

FWIW, we have soc_is_tegra() now in include/soc/tegra/common.h which is
meant to be used for exactly this purpose. I agree that it isn't optimal
but it's pretty good. It should be easy to refactor this to make it
callable from a top-level initialization function when a decision
regarding that has been made.

Thierry

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