Patchwork clk: tegra: provide dummy cpu car ops

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Submitter Peter De Schrijver
Date Feb. 14, 2013, 2:52 p.m.
Message ID <1360853581-9756-1-git-send-email-pdeschrijver@nvidia.com>
Download mbox | patch
Permalink /patch/220457/
State Superseded, archived
Headers show

Comments

Peter De Schrijver - Feb. 14, 2013, 2:52 p.m.
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?

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
---
 drivers/clk/tegra/clk.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
Stephen Warren - Feb. 14, 2013, 5:43 p.m.
On 02/14/2013 07:52 AM, Peter De Schrijver wrote:
> 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 will try and remember to apply this before the Tegra114 clock series,
although I think you're reposting that anyway, so feel free to include
this in that series to make things simpler.

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achew@nvidia.com - March 6, 2013, 11:20 p.m.
> 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?
> 
> Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> ---
>  drivers/clk/tegra/clk.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c index
> a603b9a..f6c141f 100644
> --- a/drivers/clk/tegra/clk.c
> +++ b/drivers/clk/tegra/clk.c
> @@ -22,7 +22,8 @@
>  #include "clk.h"
> 
>  /* 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;
> 
>  void __init tegra_init_dup_clks(struct tegra_clk_duplicate *dup_list,
>  				struct clk *clks[], int clk_max)
> --
> 1.7.7.rc0.72.g4b5ea.dirty
> 
> --
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Stephen Warren - March 6, 2013, 11:42 p.m.
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);

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achew@nvidia.com - March 6, 2013, 11:59 p.m.
> From: linux-tegra-owner@vger.kernel.org [mailto:linux-tegra-
> owner@vger.kernel.org] On Behalf Of Stephen Warren
> Sent: Wednesday, March 06, 2013 3:43 PM
> To: Andrew Chew
> Cc: Peter De Schrijver; linux-tegra@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; Stephen Warren; Prashant Gaikwad; Mike
> Turquette; linux-kernel@vger.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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Stephen Warren - March 7, 2013, 12:04 a.m.
On 03/06/2013 04:59 PM, Andrew Chew wrote:
>> From: linux-tegra-owner@vger.kernel.org [mailto:linux-tegra-
>> owner@vger.kernel.org] On Behalf Of Stephen Warren
>> Sent: Wednesday, March 06, 2013 3:43 PM
>> To: Andrew Chew
>> Cc: Peter De Schrijver; linux-tegra@vger.kernel.org; linux-arm-
>> kernel@lists.infradead.org; Stephen Warren; Prashant Gaikwad; Mike
>> Turquette; linux-kernel@vger.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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Patch

diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c
index a603b9a..f6c141f 100644
--- a/drivers/clk/tegra/clk.c
+++ b/drivers/clk/tegra/clk.c
@@ -22,7 +22,8 @@ 
 #include "clk.h"
 
 /* Global data of Tegra CPU CAR ops */
-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;
 
 void __init tegra_init_dup_clks(struct tegra_clk_duplicate *dup_list,
 				struct clk *clks[], int clk_max)