linux-kernel - Re: [Patch 3/3] clk: Avoid re-parenting orphan clk's having invalid parent index.

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Message-ID: <51AD9450.5090107@ti.com>
Date:	Tue, 4 Jun 2013 12:46:32 +0530
From:	Ambresh K <ambresh@...com>
To:	Mike Turquette <mturquette@...aro.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	Tero Kristo <t-kristo@...com>, Rajendra <rnayak@...com>,
	Nishanth Menon <nm@...com>
Subject: Re: [Patch 3/3] clk: Avoid re-parenting orphan clk's having invalid
 parent index.



On Wednesday 29 May 2013 12:48 PM, Mike Turquette wrote:
> Quoting Ambresh K (2013-05-01 23:25:29)
>> From: Ambresh K <ambresh@...com>
>>
>> Add orhan clk nodes having invalid parent index to list and use
>> the list to skip re-parenting orphan clk having invalid parents.
>>
>> Signed-off-by: Ambresh K <ambresh@...com>
>> ---
>>  drivers/clk/clk.c |   21 +++++++++++++++++++--
>>  1 files changed, 19 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index f4d2c73..54d2aa3 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -32,6 +32,7 @@ static int enable_refcnt;
>>  
>>  static HLIST_HEAD(clk_root_list);
>>  static HLIST_HEAD(clk_orphan_list);
>> +static HLIST_HEAD(clk_orphan_invalid_parent);
> 
> Why not re-use the clk_orphan_list?  Having an invalid value programmed
> into the hardware for selecting a parent essetially orphans a clock
> from a software point of view.  Is there a specific need for the new
> list?

Sorry for not being descriptive in commit message.  

a) Avoids unnecessary re-parenting cycle for orphan clock's with invalid parent for every clock

b) With patch [1/3], after a clk with invalid parent was encountered, for every clk registered thereafter seeing following logs. 
<Snippet>
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent
[    0.000000] __clk_init: orphan clk(gpu_core_gclk_mux) invalid parent  

Please advice, if can be handled better. 

Thanks, 
Ambresh


> 
> Regards,
> Mike
> 
>>  static LIST_HEAD(clk_notifier_list);
>>  
>>  /***           locking             ***/
>> @@ -1532,8 +1533,8 @@ EXPORT_SYMBOL_GPL(clk_set_parent);
>>   */
>>  int __clk_init(struct device *dev, struct clk *clk)
>>  {
>> -       int i, ret = 0;
>> -       struct clk *orphan;
>> +       int i, ret = 0, skip = 0;
>> +       struct clk *orphan, *has_invalid_parent;
>>         struct hlist_node *tmp2;
>>  
>>         if (!clk)
>> @@ -1639,11 +1640,27 @@ int __clk_init(struct device *dev, struct clk *clk)
>>                 if (!strcmp(clk->name, orphan->name))
>>                         continue;
>>  
>> +               /* Skip iteration if orphan has invalid parent */
>> +               hlist_for_each_entry(has_invalid_parent,
>> +                               &clk_orphan_invalid_parent, child_node) {
>> +                       if (!strcmp(orphan->name, has_invalid_parent->name)) {
>> +                               skip = 1;
>> +                               break;
>> +                       }
>> +               }
>> +
>> +               if (skip) {
>> +                       skip = 0;
>> +                       continue;
>> +               }
>> +
>>                 if (orphan->ops->get_parent) {
>>                         i = orphan->ops->get_parent(orphan->hw);
>>                         if (i < 0) {
>>                                 pr_err("%s: orphan clk(%s) invalid parent\n",
>>                                                 __func__, orphan->name);
>> +                               hlist_add_head(&orphan->child_node,
>> +                                               &clk_orphan_invalid_parent);
>>                                 continue;
>>                         }
>>                         if (!strcmp(clk->name, orphan->parent_names[i]))
>> -- 
>> 1.7.4.1
> 
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