linux-kernel - RE: [PATCH] clk: tegra: provide dummy cpu car ops

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Date:	Wed, 6 Mar 2013 15:59:04 -0800
From:	Andrew Chew <AChew@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	Peter De Schrijver <pdeschrijver@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stephen Warren <swarren@...dia.com>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] clk: tegra: provide dummy cpu car ops

> From: linux-tegra-owner@...r.kernel.org [mailto:linux-tegra-
> owner@...r.kernel.org] On Behalf Of Stephen Warren
> Sent: Wednesday, March 06, 2013 3:43 PM
> To: Andrew Chew
> Cc: Peter De Schrijver; linux-tegra@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; Stephen Warren; Prashant Gaikwad; Mike
> Turquette; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] clk: tegra: provide dummy cpu car ops
> 
> On 03/06/2013 04:20 PM, Andrew Chew wrote:
> >> Subject: [PATCH] clk: tegra: provide dummy cpu car ops
> >>
> >> tegra_boot_secondary() relies on some of the car ops. This means
> >> having an uninitialized tegra_cpu_car_ops will lead to an early boot panic.
> >> Providing a dummy struct avoids this and makes adding Tegra114 clock
> >> support in a bisectable way a lot easier.
> >>
> >> --
> >>
> >> Stephen,
> >>
> >> Should this be a separate patch or should I make this part of new
> >> release of the Tegra114 clock series?
> 
> I'm not sure if I answered this. Peter, I intend to apply this patch to a branch
> right before the CCF, so there's no explicit need to include it in the series,
> although if you do, that's fine.
> 
> >> diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c index
> 
> >>  /* Global data of Tegra CPU CAR ops */ -struct tegra_cpu_car_ops
> >> *tegra_cpu_car_ops;
> >
> > Sorry for bringing this up so late...
> > Shouldn't the above be "struct tegra_cpu_car_ops tegra_cpu_car_ops;"?
> >
> >> +static struct tegra_cpu_car_ops *dummy_car_ops; struct
> >> +tegra_cpu_car_ops *tegra_cpu_car_ops = &dummy_car_ops;
> 
> No, the value is used as a pointer in include/linux/clk/tegra.h, e.g.:
> 
> tegra_cpu_car_ops->wait_for_reset(cpu);

Yeah, I get that tegra_cpu_car_ops is a pointer to an ops table.  It seems
to me that what's happening above is that tegra_cpu_car_ops is getting
assigned a pointer to a pointer that's supposed to point to an instance of
struct tegra_cpu_car_ops (but it really points to NULL as far as I can tell).
In any case, dummy_car_ops never actually gets instantiated.

I assume the intention is for dummy_car_ops to be an instance of
struct tegra_cpu_car_ops, but with all of its members zero'd.
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