[RFC] opp: Fixup release of clock when using set/put clkname

[RFC] opp: Fixup release of clock when using set/put clkname

[Rajendra Nayak]

Fixup dev_pm_opp_put_clkname() to check for a valid clock pointer
before it does a clk_put, since its likely that
_opp_table_kref_release() has already done a clk_put. Also fixup
_opp_table_kref_release() to set the clock pointer to ERR_PTR(-EINVAL)
after its done doing a clk_put so dev_pm_opp_put_clkname() can then
catch it.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
---
 drivers/opp/core.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index e4f01e7..6d064a8 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1061,8 +1061,10 @@ static void _opp_table_kref_release(struct kref *kref)
 	_of_clear_opp_table(opp_table);
 
 	/* Release clk */
-	if (!IS_ERR(opp_table->clk))
+	if (!IS_ERR(opp_table->clk)) {
 		clk_put(opp_table->clk);
+		opp_table->clk = ERR_PTR(-EINVAL);
+	}
 
 	WARN_ON(!list_empty(&opp_table->opp_list));
 
@@ -1744,8 +1746,10 @@ void dev_pm_opp_put_clkname(struct opp_table *opp_table)
 	/* Make sure there are no concurrent readers while updating opp_table */
 	WARN_ON(!list_empty(&opp_table->opp_list));
 
-	clk_put(opp_table->clk);
-	opp_table->clk = ERR_PTR(-EINVAL);
+	if (!IS_ERR(opp_table->clk)) {
+		clk_put(opp_table->clk);
+		opp_table->clk = ERR_PTR(-EINVAL);
+	}
 
 	dev_pm_opp_put_opp_table(opp_table);
 }
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [RFC] opp: Fixup release of clock when using set/put clkname

[Viresh Kumar]

On 14-04-20, 12:45, Rajendra Nayak wrote:
> Fixup dev_pm_opp_put_clkname() to check for a valid clock pointer
> before it does a clk_put, since its likely that
> _opp_table_kref_release() has already done a clk_put. Also fixup

kref release is the last thing that happens on the table, it can't get
called after dev_pm_opp_put_clkname().

> _opp_table_kref_release() to set the clock pointer to ERR_PTR(-EINVAL)
> after its done doing a clk_put so dev_pm_opp_put_clkname() can then
> catch it.
> 
> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> ---
>  drivers/opp/core.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index e4f01e7..6d064a8 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1061,8 +1061,10 @@ static void _opp_table_kref_release(struct kref *kref)
>  	_of_clear_opp_table(opp_table);
>  
>  	/* Release clk */
> -	if (!IS_ERR(opp_table->clk))
> +	if (!IS_ERR(opp_table->clk)) {
>  		clk_put(opp_table->clk);
> +		opp_table->clk = ERR_PTR(-EINVAL);
> +	}
>  
>  	WARN_ON(!list_empty(&opp_table->opp_list));
>  
> @@ -1744,8 +1746,10 @@ void dev_pm_opp_put_clkname(struct opp_table *opp_table)
>  	/* Make sure there are no concurrent readers while updating opp_table */
>  	WARN_ON(!list_empty(&opp_table->opp_list));
>  
> -	clk_put(opp_table->clk);
> -	opp_table->clk = ERR_PTR(-EINVAL);
> +	if (!IS_ERR(opp_table->clk)) {
> +		clk_put(opp_table->clk);
> +		opp_table->clk = ERR_PTR(-EINVAL);
> +	}
>  
>  	dev_pm_opp_put_opp_table(opp_table);
>  }
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation

-- 
viresh

Re: [RFC] opp: Fixup release of clock when using set/put clkname

[Rajendra Nayak]

On 4/14/2020 12:48 PM, Viresh Kumar wrote:
> On 14-04-20, 12:45, Rajendra Nayak wrote:
>> Fixup dev_pm_opp_put_clkname() to check for a valid clock pointer
>> before it does a clk_put, since its likely that
>> _opp_table_kref_release() has already done a clk_put. Also fixup
> 
> kref release is the last thing that happens on the table, it can't get
> called after dev_pm_opp_put_clkname().

so in cases where I do have an OPP table for a device in DT and I do
dev_pm_opp_set_clkname()
dev_pm_opp_of_add_table()

and clean it up with a
dev_pm_opp_of_remove_table()
dev_pm_opp_put_clkname()

things seem to work fine as expected.

However, given I call these unconditionally in common drivers and on
some (old) platforms we really don't have an OPP table (only scale clocks)
things get a little tricky. So looks like the ref counting in such cases
gets messed up, and we end up with dev_pm_opp_of_remove_table() calling
_opp_table_kref_release() and releasing the clock, and then the subsequent
call to dev_pm_opp_put_clkname() crashes.

>> _opp_table_kref_release() to set the clock pointer to ERR_PTR(-EINVAL)
>> after its done doing a clk_put so dev_pm_opp_put_clkname() can then
>> catch it.
>>
>> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
>> ---
>>   drivers/opp/core.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>> index e4f01e7..6d064a8 100644
>> --- a/drivers/opp/core.c
>> +++ b/drivers/opp/core.c
>> @@ -1061,8 +1061,10 @@ static void _opp_table_kref_release(struct kref *kref)
>>   	_of_clear_opp_table(opp_table);
>>   
>>   	/* Release clk */
>> -	if (!IS_ERR(opp_table->clk))
>> +	if (!IS_ERR(opp_table->clk)) {
>>   		clk_put(opp_table->clk);
>> +		opp_table->clk = ERR_PTR(-EINVAL);
>> +	}
>>   
>>   	WARN_ON(!list_empty(&opp_table->opp_list));
>>   
>> @@ -1744,8 +1746,10 @@ void dev_pm_opp_put_clkname(struct opp_table *opp_table)
>>   	/* Make sure there are no concurrent readers while updating opp_table */
>>   	WARN_ON(!list_empty(&opp_table->opp_list));
>>   
>> -	clk_put(opp_table->clk);
>> -	opp_table->clk = ERR_PTR(-EINVAL);
>> +	if (!IS_ERR(opp_table->clk)) {
>> +		clk_put(opp_table->clk);
>> +		opp_table->clk = ERR_PTR(-EINVAL);
>> +	}
>>   
>>   	dev_pm_opp_put_opp_table(opp_table);
>>   }
>> -- 
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
>> of Code Aurora Forum, hosted by The Linux Foundation
> 

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [RFC] opp: Fixup release of clock when using set/put clkname

[Viresh Kumar]

On 14-04-20, 20:35, Rajendra Nayak wrote:
> However, given I call these unconditionally in common drivers and on
> some (old) platforms we really don't have an OPP table (only scale clocks)
> things get a little tricky. So looks like the ref counting in such cases
> gets messed up, and we end up with dev_pm_opp_of_remove_table() calling
> _opp_table_kref_release() and releasing the clock, and then the subsequent
> call to dev_pm_opp_put_clkname() crashes.

We aren't supposed to call dev_pm_opp_of_remove_table() if
dev_pm_opp_of_add_table() isn't called or it failed. Either we can
handle this in core, which I would like to avoid, or just keep a
variable to track it in the driver, which will be easy enough I guess.

-- 
viresh