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

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Message-ID: <5137D991.7080808@wwwdotorg.org>
Date:	Wed, 06 Mar 2013 17:04:33 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Andrew Chew <AChew@...dia.com>
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

On 03/06/2013 04:59 PM, Andrew Chew wrote:
>> 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.

Oh right, I guess your comment was about the line after where you wrote
it rather than the line before.

So, you mean:

static struct tegra_cpu_car_ops *dummy_car_ops;
struct tegra_cpu_car_ops *tegra_cpu_car_ops = &dummy_car_ops;

should be instead:

static struct tegra_cpu_car_ops dummy_car_ops;
struct tegra_cpu_car_ops *tegra_cpu_car_ops = &dummy_car_ops;

Yes, you're right.
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