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Date: Thu, 4 Apr 2024 20:10:09 -0700
From: Bjorn Andersson <quic_bjorande@quicinc.com>
To: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
CC: <konrad.dybcio@linaro.org>, <andersson@kernel.org>,
        <andi.shyti@kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-i2c@vger.kernel.org>,
        <quic_vdadhani@quicinc.com>, Vinod Koul <vkoul@kernel.org>
Subject: Re: [PATCH v1] i2c: i2c-qcom-geni: Serve transfer during early
 resume stage
Message-ID: <Zg9rkXddNC+G36O8@hu-bjorande-lv.qualcomm.com>
References: <20240328123743.1713696-1-quic_msavaliy@quicinc.com>
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In-Reply-To: <20240328123743.1713696-1-quic_msavaliy@quicinc.com>

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"?

> +		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.

Do you really get through this with things balanced?

> +		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...

> +			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...

> +			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?

> +		}
>  	}
>  
>  	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.

> +	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()?

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
>