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

[Mukesh Kumar Savaliya]

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@xxxxxxxxxxx>
> > Signed-off-by: Viken Dadhaniya <quic_vdadhani@xxxxxxxxxxx>
> > Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@xxxxxxxxxxx>
> > ---
> >   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