Re: AM335x OMAP2 common clock external fixed-clock registration

Sebastian Hesselbarth
2015-04-16T20:37:30Z

On 16.04.2015 18:17, Michael Welling wrote:
> On Thu, Apr 16, 2015 at 07:32:32AM +0300, Tero Kristo wrote:
>> On 04/15/2015 11:51 PM, Michael Welling wrote:
>>> On Wed, Apr 15, 2015 at 01:45:53PM -0700, Mike Turquette wrote:
>>>> On Wed, Apr 15, 2015 at 12:47 PM, Michael Welling <mwelling@ieee.org> wrote:
[...]
>>>>> There is still an issue with the si5351.
>>>>>
>>>>> I had to comment out the clk_put here for the frequency to show up:
>>>>> http://lxr.free-electrons.com/source/drivers/clk/clk-si5351.c#L1133
>>>>>
>>>>> Ideas?
>>>>
>>>> What is the most recent upstream commit that you are based on?
>>>
>>> I am working from 4.0.0-rc7.
>>>
>>> 7b43b47373d40d557cd7e1a84a0bd8ebc4d745ab
>>
>> Hmm, I wonder why si5351 calls clk_put immediately after of_clk_get
>> in the first place, as far as I understand this destroys the clock
>> handle, which is still being used later in the code.
>
> Not sure how this ever worked. This has been in the code since the
> initial commit.

The reason it worked before may be related with recent rework of
clk_put() itself and clk cookies instead of pointers. I lost track on
the recent clk subsystem changes here, sorry.

However, droping the clk immediately surely isn't right.
The thing is, we can remove the clk_put() just because there is no
_remove() for that driver. I remember that back in the days the driver
was mainlined, clk removal wasn't too easy.

FWIW, as soon as _remove() support will be added by someone, we'll have
to rethink passing struct clk* by platform_data or at least
double-check if we ever used [of_]clk_get() to obtain it.

Mind to send a patch removing the clk_put() on !IS_ERR and add a proper
error path instead? While of_clk_get() is the only calls that need
cleanup on error in si5351_dt_parse() we should probably move that
calls to the end of this function. Otherwise we'd also have to cleanup
on every of_parse_foo() failure.

Sebastian