linux-kernel - Re: [PATCH] clk: add strict of_clk

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Date:	Wed, 05 Feb 2014 16:07:19 +0100
From:	Boris BREZILLON <b.brezillon@...rkiz.com>
To:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
CC:	Mike Turquette <mturquette@...aro.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Jason Cooper <jason@...edaemon.net>,
	linux-kernel@...r.kernel.org,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH] clk: add strict of_clk_init dependency check

On 05/02/2014 16:05, Gregory CLEMENT wrote:
> On 05/02/2014 15:48, Gregory CLEMENT wrote:
>> Hi Boris,
>>
>> On 05/02/2014 10:48, Boris BREZILLON wrote:
>>> The parent dependency check is only available on the first parent of a given
>>> clk.
>>>
>>> Add support for strict dependency check: all parents of a given clk must be
>>> initialized.
>>>
>>> Signed-off-by: Boris BREZILLON <b.brezillon@...rkiz.com>
>>> ---
>>>
>>> Hello Gregory,
>>>
>>> This patch adds support for strict check on clk dependencies (check if all
>>> parents specified by an DT clk node are initialized).
>>>
>>> I'm not sure this is what you were expecting (maybe testing the first parent
>>> is what you really want), so please feel free to tell me if I'm wrong.
>>>
>>> Best Regards,
>>>
>>> Boris
>>>
>>>   drivers/clk/clk.c |   27 +++++++++++++++++++++------
>>>   1 file changed, 21 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>>> index beb0f8b..6849769 100644
>>> --- a/drivers/clk/clk.c
>>> +++ b/drivers/clk/clk.c
>>> @@ -2543,22 +2543,37 @@ static int parent_ready(struct device_node *np)
>>>   {
>>>   	struct of_phandle_args clkspec;
>>>   	struct of_clk_provider *provider;
>>> +	int num_parents;
>>> +	bool found;
>>> +	int i;
>>>   
>>>   	/*
>>>   	 * If there is no clock parent, no need to wait for them, then
>>>   	 * we can consider their absence as being ready
>>>   	 */
>>> -	if (of_parse_phandle_with_args(np, "clocks", "#clock-cells", 0,
>>> -					&clkspec))
>>> +	num_parents = of_count_phandle_with_args(np, "clocks", "#clock-cells");
>>> +	if (num_parents <= 0)
>>>   		return 1;
>>>   
>>> -	/* Check if we have such a provider in our array */
>>> -	list_for_each_entry(provider, &of_clk_providers, link) {
>>> -		if (provider->node == clkspec.np)
>>> +	for (i = 0; i < num_parents; i++) {
>>> +		if (of_parse_phandle_with_args(np, "clocks", "#clock-cells", i,
>>> +					       &clkspec))
>>>   			return 1;
>>> +
>>> +		/* Check if we have such a provider in our array */
>>> +		found = false;
>>> +		list_for_each_entry(provider, &of_clk_providers, link) {
>>> +			if (provider->node == clkspec.np) {
>>> +				found = true;
>>> +				break;
>> Hum this means that as soon as you have one parent then you consider it
>> as ready. It is better of what I have done because I only test the 1st
>> parent. However I wondered if we should go further by ensuring all the
>> parents are ready.
> My bad, I read the code too fast. Your code already checks that all the
> parents are ready.
>
> So if you agree I will merge your code with mine and send a new patch.

That's fine by me.
>
>> If I am right, there is more than one parent only for the muxer. In this
>> case is it really expected that all the parent are ready?
>>
>> Thanks,
>>
>> Gregory
>>
>>> +			}
>>> +		}
>>> +
>>> +		if (!found)
>>> +			return 0;
>>>   	}
>>>   
>>> -	return 0;
>>> +	return 1;
>>>   }
>>>   
>>>   /**
>>>
>>
>

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