linux-kernel - [PATCH v3] i2c: i2c-qcom-geni: Serve transfer during early resume stage

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Message-Id: <20241119143031.3331753-1-quic_msavaliy@quicinc.com>
Date: Tue, 19 Nov 2024 20:00:31 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: andi.shyti@...nel.org, quic_bjorande@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, --cc=konrad.dybcio@...aro.org,
        quic_vdadhani@...cinc.com, vkoul@...nel.org
Cc: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Subject: [PATCH v3] i2c: i2c-qcom-geni: Serve transfer during early resume stage

pm_runtime_get_sync() function fails during PM early resume and returns
-EACCES because runtime PM for the device is disabled at the early stage
causing i2c transfer to fail. Make changes to serve transfer with forced
resume.

Few i2c clients like PCI OR touch may request i2c transfers during early
resume stage. Any i2c client can keep transfer request very early resume
stage like noirq phase of PM. To serve the transfer, register an interrupt
with IRQF_EARLY_RESUME and IRQF_NO_SUSPEND flags to avoid timeout of
transfer when IRQ is not enabled during early stage.

pm_runtime_get_sync() fails when runtime PM is not enabled, then use
pm_runtime_force_resume() and serve the transfer.

Co-developed-by: Viken Dadhaniya <quic_vdadhani@...cinc.com>
Signed-off-by: Viken Dadhaniya <quic_vdadhani@...cinc.com>
Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
---

Link to V2: https://lore.kernel.org/lkml/202410132233.P25W2vKq-lkp@intel.com/T/

 v2 -> v3:
 - Updated exact usecase and scenario in the commit log description.
 - Removed bulleted points from technical description, added details in free flow.
 - Used pm_runtime_force_resume/suspend() instead customized local implementation.
 - Added debug log after pm_runtime_force_suspend().

---
Link to V1: https://patches.linaro.org/project/linux-i2c/patch/20240328123743.1713696-1-quic_msavaliy@quicinc.com/

 v1 -> v2:
 - Changed gi2c->se.dev to dev during dev_dbg() calls.
 - Addressed review comments from Andi and Bjorn.
 - Returned 0 instead garbage inside geni_i2c_force_resume().
 - Added comments explaining forced resume transfer when runtime PM
   remains disabled.
---

 drivers/i2c/busses/i2c-qcom-geni.c | 43 +++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 12 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 7a22e1f46e60..4fe5fa4532ca 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -695,17 +695,27 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
 			 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;
+	/* Serve I2C transfer by forced resume if Runtime PM is enbled or not */
+	if (!pm_runtime_enabled(dev) && gi2c->suspended) {
+		dev_dbg(dev, "Runtime PM is disabled hence force resume, pm_usage_count: %d\n",
+			atomic_read(&dev->power.usage_count));
+		ret = pm_runtime_force_resume(dev);
+		if (ret)
+			return ret;
+	} else {
+		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;
+		}
 	}
 
 	qcom_geni_i2c_conf(gi2c);
@@ -715,8 +725,18 @@ 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);
+	/* if Runtime PM is disabled, do force_suspend() else autosuspend the driver */
+	if (!pm_runtime_enabled(dev) && !gi2c->suspended) {
+		ret = pm_runtime_force_suspend(dev);
+		dev_dbg(dev, "Runtime PM is disabled hence force suspend, pm_usage_count: %d\n",
+			atomic_read(&dev->power.usage_count));
+		if (ret)
+			return ret;
+	} else {
+		pm_runtime_mark_last_busy(gi2c->se.dev);
+		pm_runtime_put_autosuspend(gi2c->se.dev);
+	}
+
 	gi2c->cur = NULL;
 	gi2c->err = 0;
 	return ret;
@@ -833,9 +853,8 @@ static int geni_i2c_probe(struct platform_device *pdev)
 	init_completion(&gi2c->done);
 	spin_lock_init(&gi2c->lock);
 	platform_set_drvdata(pdev, gi2c);
-
-	/* Keep interrupts disabled initially to allow for low-power modes */
-	ret = devm_request_irq(dev, gi2c->irq, geni_i2c_irq, IRQF_NO_AUTOEN,
+	ret = devm_request_irq(dev, gi2c->irq, geni_i2c_irq,
+			       IRQF_NO_AUTOEN | 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