linux-kernel - Re: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and

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Date: Wed, 26 Jun 2024 09:30:52 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Biju Das <biju.das.jz@...renesas.com>,
 Chris Brandt <Chris.Brandt@...esas.com>,
 "andi.shyti@...nel.org" <andi.shyti@...nel.org>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "geert+renesas@...der.be" <geert+renesas@...der.be>,
 "magnus.damm@...il.com" <magnus.damm@...il.com>,
 "mturquette@...libre.com" <mturquette@...libre.com>,
 "sboyd@...nel.org" <sboyd@...nel.org>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>
Cc: "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()



On 26.06.2024 09:23, Biju Das wrote:
> 
> 
>> -----Original Message-----
>> From: claudiu beznea <claudiu.beznea@...on.dev>
>> Sent: Wednesday, June 26, 2024 7:14 AM
>> To: Biju Das <biju.das.jz@...renesas.com>; Chris Brandt <Chris.Brandt@...esas.com>;
>> andi.shyti@...nel.org; robh@...nel.org; krzk+dt@...nel.org; conor+dt@...nel.org;
>> geert+renesas@...der.be; magnus.damm@...il.com; mturquette@...libre.com; sboyd@...nel.org;
>> p.zabel@...gutronix.de; wsa+renesas@...g-engineering.com
>> Cc: linux-renesas-soc@...r.kernel.org; linux-i2c@...r.kernel.org; devicetree@...r.kernel.org;
>> linux-kernel@...r.kernel.org; linux-clk@...r.kernel.org; Claudiu Beznea
>> <claudiu.beznea.uj@...renesas.com>
>> Subject: Re: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()
>>
>> Hi, Biju,
>>
>> On 25.06.2024 18:53, Biju Das wrote:
>>> Hi Claudiu,
>>>
>>>> -----Original Message-----
>>>> From: Claudiu <claudiu.beznea@...on.dev>
>>>> Sent: Tuesday, June 25, 2024 1:14 PM
>>>> Subject: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()
>>>>
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> pm_runtime_get_sync() may return with error. In case it returns with
>>>> error
>>>> dev->power.usage_count needs to be decremented.
>>>> dev->pm_runtime_resume_and_get()
>>>> takes care of this. Thus use it.
>>>>
>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>> ---
>>>>
>>>> Changes in v2:
>>>> - delete i2c adapter all the time in remove
>>>>
>>>>  drivers/i2c/busses/i2c-riic.c | 30 ++++++++++++++++++++++++------
>>>>  1 file changed, 24 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-riic.c
>>>> b/drivers/i2c/busses/i2c-riic.c index 83e4d5e14ab6..002b11b020fa
>>>> 100644
>>>> --- a/drivers/i2c/busses/i2c-riic.c
>>>> +++ b/drivers/i2c/busses/i2c-riic.c
>>>> @@ -113,6 +113,8 @@ struct riic_irq_desc {
>>>>  	char *name;
>>>>  };
>>>>
>>>> +static const char * const riic_rpm_err_msg = "Failed to runtime
>>>> +resume";
>>>> +
>>>>  static inline void riic_writeb(struct riic_dev *riic, u8 val, u8 offset)  {
>>>>  	writeb(val, riic->base + riic->info->regs[offset]); @@ -133,10
>>>> +135,14 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>>>>  	struct riic_dev *riic = i2c_get_adapdata(adap);
>>>>  	struct device *dev = adap->dev.parent;
>>>>  	unsigned long time_left;
>>>> -	int i;
>>>> +	int i, ret;
>>>>  	u8 start_bit;
>>>>
>>>> -	pm_runtime_get_sync(dev);
>>>> +	ret = pm_runtime_resume_and_get(dev);
>>>> +	if (ret) {
>>>> +		dev_err(dev, riic_rpm_err_msg);
>>>
>>> As at the moment we don't know how to reproduce this error condition
>>> Can we use WARN_ON_ONCE() instead to catch detailed error condition here??
>>
>> [1] states "So, naturally, use of WARN_ON() is also now discouraged much of the time". I've go with
>> dev_err() or something similar.
> 
> WARN_ON_ONCE() should be ok I guess as people are using for printing this info only once??

Ok, I'm leaving this to I2C maintainers.

Andi, Wolfram,

Would you prefer having WARN_ON_ONCE() instead of dev_err() for potential
failures of pm_runtime_resume_and_get()?

Thank you,
Claudiu Beznea

> 
> Currently we don't know how to trigger pm_runtime_resume_and_get() error 
> condition in our setup using a testapp and we are expecting an error may
> happen in future. If at all there is an error in future, we need detailed
> error info so that we can handle it and fix the bug.
> 
> Cheers,
> Biju
> 
>>
>> Thank you,
>> Claudiu Beznea
>>
>> [1] https://lwn.net/Articles/969923/
>>
>>>
>>> Cheers,
>>> Biju
>>>
>>>> +		return ret;
>>>> +	}
>>>>
>>>>  	if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) {
>>>>  		riic->err = -EBUSY;
>>>> @@ -301,6 +307,7 @@ static const struct i2c_algorithm riic_algo = {
>>>>
>>>>  static int riic_init_hw(struct riic_dev *riic, struct i2c_timings
>>>> *t)  {
>>>> +	int ret;
>>>>  	unsigned long rate;
>>>>  	int total_ticks, cks, brl, brh;
>>>>  	struct device *dev = riic->adapter.dev.parent; @@ -379,7 +386,11 @@
>>>> static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
>>>>  		 t->scl_fall_ns / (1000000000 / rate),
>>>>  		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);
>>>>
>>>> -	pm_runtime_get_sync(dev);
>>>> +	ret = pm_runtime_resume_and_get(dev);
>>>> +	if (ret) {
>>>> +		dev_err(dev, riic_rpm_err_msg);
>>>> +		return ret;
>>>> +	}
>>>>
>>>>  	/* Changing the order of accessing IICRST and ICE may break things! */
>>>>  	riic_writeb(riic, ICCR1_IICRST | ICCR1_SOWP, RIIC_ICCR1); @@
>>>> -498,11 +509,18 @@ static void riic_i2c_remove(struct platform_device *pdev)  {
>>>>  	struct riic_dev *riic = platform_get_drvdata(pdev);
>>>>  	struct device *dev = &pdev->dev;
>>>> +	int ret;
>>>>
>>>> -	pm_runtime_get_sync(dev);
>>>> -	riic_writeb(riic, 0, RIIC_ICIER);
>>>> -	pm_runtime_put(dev);
>>>>  	i2c_del_adapter(&riic->adapter);
>>>> +
>>>> +	ret = pm_runtime_resume_and_get(dev);
>>>> +	if (ret) {
>>>> +		dev_err(dev, riic_rpm_err_msg);
>>>> +	} else {
>>>> +		riic_writeb(riic, 0, RIIC_ICIER);
>>>> +		pm_runtime_put(dev);
>>>> +	}
>>>> +
>>>>  	pm_runtime_disable(dev);
>>>>  }
>>>>
>>>> --
>>>> 2.39.2
>>>>
>>>