Re: [PATCH v1] i2c: i2c-qcom-geni: Serve transfer during early resume stage

[Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>]

Thanks Bjorn for the review.

On 4/5/2024 8:40 AM, Bjorn Andersson wrote:
> On Thu, Mar 28, 2024 at 06:07:43PM +0530, Mukesh Kumar Savaliya wrote:
>> pm_runtime_get_sync() function fails during PM early resume and returning
>> -EACCES because runtime PM for the device is disabled at the early stage
>> causing i2c transfer to fail. Make changes to serve transfer with force
>> resume.
>>
>> 1. Register interrupt with IRQF_EARLY_RESUME and IRQF_NO_SUSPEND flags
>>     to avoid timeout of transfer when IRQ is not enabled during early stage.
>> 2. Do force resume if pm_runtime_get_sync() is failing after system
>>     suspend when runtime PM is not enabled.
>> 3. Increment power usage count after forced resume to balance
>>     it against regular runtime suspend.
>>
>> Co-developed-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
>> Signed-off-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>> ---
>>   drivers/i2c/busses/i2c-qcom-geni.c | 55 ++++++++++++++++++++++++------
>>   1 file changed, 45 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
>> index da94df466e83..ed8201983a03 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -134,6 +134,8 @@ struct geni_i2c_clk_fld {
>>   	u8	t_cycle_cnt;
>>   };
>>   
>> +static int geni_i2c_runtime_resume(struct device *dev);
>> +
>>   /*
>>    * Hardware uses the underlying formula to calculate time periods of
>>    * SCL clock cycle. Firmware uses some additional cycles excluded from the
>> @@ -677,22 +679,48 @@ static int geni_i2c_fifo_xfer(struct geni_i2c_dev *gi2c,
>>   	return num;
>>   }
>>   
>> +static int geni_i2c_force_resume(struct geni_i2c_dev *gi2c)
>> +{
>> +	struct device *dev = gi2c->se.dev;
>> +	int ret;
>> +
>> +	ret = geni_i2c_runtime_resume(dev);
>> +	if (ret) {
>> +		dev_err(gi2c->se.dev, "Error turning SE resources:%d\n", ret);
> 
> "error turning"? How about "Failed to enable SE resources: %d\n"?
Sounds good, Thanks. Made this change.
> 
>> +		pm_runtime_put_noidle(dev);
>> +		pm_runtime_set_suspended(dev);
> 
> These two where the error-handling for pm_runtime_get_sync() failing, in
> one case below you get here after pm_runtime_get_sync() failed in the
> other you have not attempted to call that function.
> 
Hi Bjorn, could you please clarify further on this question ? I am not 
getting two instances for failure of pm_runtime_get_sync().
> Do you really get through this with things balanced?
We haven't seen imbalance in the usage count with added debug logs locally.
> 
>> +		return ret;
>> +	}
>> +	pm_runtime_get_noresume(dev);
>> +	pm_runtime_set_active(dev);
>> +	return ret;
> 
> ret is 0.
> 
>> +}
>> +
>>   static int geni_i2c_xfer(struct i2c_adapter *adap,
>>   			 struct i2c_msg msgs[],
>>   			 int num)
>>   {
>>   	struct geni_i2c_dev *gi2c = i2c_get_adapdata(adap);
>> +	struct device *dev = gi2c->se.dev;
>>   	int ret;
>>   
>>   	gi2c->err = 0;
>>   	reinit_completion(&gi2c->done);
>> -	ret = pm_runtime_get_sync(gi2c->se.dev);
>> -	if (ret < 0) {
>> -		dev_err(gi2c->se.dev, "error turning SE resources:%d\n", ret);
>> -		pm_runtime_put_noidle(gi2c->se.dev);
>> -		/* Set device in suspended since resume failed */
>> -		pm_runtime_set_suspended(gi2c->se.dev);
>> -		return ret;
>> +
>> +	if (!pm_runtime_enabled(dev) && gi2c->suspended) {
>> +		dev_dbg(gi2c->se.dev, "RT_PM disabled, Do force resume, usage_count:%d\n",
> 
> "RT_PM" is not a widely used abbreviation for this...
Agree. Modified as "Runtime PM is disabled"
> 
>> +			atomic_read(&dev->power.usage_count));
>> +		ret = geni_i2c_force_resume(gi2c);
>> +		if (ret)
>> +			return ret;
>> +	} else {
>> +		ret = pm_runtime_get_sync(dev);
>> +		if (ret == -EACCES && gi2c->suspended) {
>> +			dev_dbg(gi2c->se.dev, "PM get_sync() failed-%d, force resume\n", ret);
> 
> Different abbreviation, different formatting of error value in log
> line...
yes, improved as ""pm_runtime_get_sync() failed"
> 
>> +			ret = geni_i2c_force_resume(gi2c);
>> +			if (ret)
>> +				return ret;
> 
> This chunk looks identical to the chunk above, can this somehow be
> restructured to avoid the duplication?
I see different failure condition and then conditional call to 
geni_i2c_force_resume(). Could you please highlight exact optimization ?
> 
>> +		}
>>   	}
>>   
>>   	qcom_geni_i2c_conf(gi2c);
>> @@ -702,8 +730,15 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
>>   	else
>>   		ret = geni_i2c_fifo_xfer(gi2c, msgs, num);
>>   
>> -	pm_runtime_mark_last_busy(gi2c->se.dev);
>> -	pm_runtime_put_autosuspend(gi2c->se.dev);
> 
> I'm not sure I follow this part, please add a comment here for the
> future reader.
sure, Added comment in next patch.

> 
>> +	if (!pm_runtime_enabled(dev) && !gi2c->suspended) {
>> +		pm_runtime_put_noidle(dev);
>> +		pm_runtime_set_suspended(dev);
>> +		gi2c->suspended = 0;
> 
> Why alter suspended flag in xfer()?
> 
Because force_resume() makes it active with respect to the
> Regards,
> Bjorn
> 
>> +	} else {
>> +		pm_runtime_mark_last_busy(gi2c->se.dev);
>> +		pm_runtime_put_autosuspend(gi2c->se.dev);
>> +	}
>> +
>>   	gi2c->cur = NULL;
>>   	gi2c->err = 0;
>>   	return ret;
>> @@ -820,7 +855,7 @@ static int geni_i2c_probe(struct platform_device *pdev)
>>   	init_completion(&gi2c->done);
>>   	spin_lock_init(&gi2c->lock);
>>   	platform_set_drvdata(pdev, gi2c);
>> -	ret = devm_request_irq(dev, gi2c->irq, geni_i2c_irq, 0,
>> +	ret = devm_request_irq(dev, gi2c->irq, geni_i2c_irq, IRQF_EARLY_RESUME | IRQF_NO_SUSPEND,
>>   			       dev_name(dev), gi2c);
>>   	if (ret) {
>>   		dev_err(dev, "Request_irq failed:%d: err:%d\n",
>> -- 
>> 2.25.1
>>