[Patch V8] i2c: imx: add runtime pm support to improve the performance

[Patch V8] i2c: imx: add runtime pm support to improve the performance

[Gao Pan]

In our former i2c driver, i2c clk is enabled and disabled in
xfer function, which contributes to power saving. However,
the clk enable process brings a busy wait delay until the core
is stable. As a result, the performance is sacrificed.

To weigh the power consumption and i2c bus performance, runtime
pm is the good solution for it. The clk is enabled when a i2c
transfer starts, and disabled after a specifically defined delay.

Without the patch the test case (many eeprom reads) executes with approx:
real 1m7.735s
user 0m0.488s
sys 0m20.040s

With the patch the same test case (many eeprom reads) executes with approx:
real 0m54.241s
user 0m0.440s
sys 0m5.920s

Signed-off-by: Fugang Duan <B38611-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
Signed-off-by: Gao Pan <b54642-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
---
V2:
As Uwe Kleine-König's suggestion, the version do below changes:
 -call clk_prepare_enable in probe to avoid never enabling clock
  if CONFIG_PM is disabled
 -enable clock before request IRQ in probe
 -remove the pm staff in i2c_imx_isr

V3:
 -pm_runtime_get_sync returns < 0 as error

V4:
 -add pm_runtime_set_active before pm_runtime_enable
 -replace pm_runtime_put_autosuspend with pm_runtime_autosuspend
  in probe
 -add error disposal when i2c_add_numbered_adapter fails

V5:
 -clean up and disable runtime PM when i2c_add_numbered_adapter fails
 -use pm_runtime_get and pm_runtime_put_autosuspend in probe

V6:
 -disable the clock manually and set the state to suspended explicitly with
  pm_runtime_set_suspended

V7:
 -manually disabling the clock and use pm_runtime_put_noidle in the remove callback

V8:
 -move out label after the two runtime pm calls in i2c_imx_xfer

 drivers/i2c/busses/i2c-imx.c | 90 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 78 insertions(+), 12 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 785aa67..91bdf28 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -53,6 +53,7 @@
 #include <linux/platform_device.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/pm_runtime.h>
 
 /** Defines ********************************************************************
 *******************************************************************************/
@@ -118,6 +119,8 @@
 #define I2CR_IEN_OPCODE_0	0x0
 #define I2CR_IEN_OPCODE_1	I2CR_IEN
 
+#define I2C_PM_TIMEOUT		10 /* ms */
+
 /** Variables ******************************************************************
 *******************************************************************************/
 
@@ -520,9 +523,6 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
 
 	i2c_imx_set_clk(i2c_imx);
 
-	result = clk_prepare_enable(i2c_imx->clk);
-	if (result)
-		return result;
 	imx_i2c_write_reg(i2c_imx->ifdr, i2c_imx, IMX_I2C_IFDR);
 	/* Enable I2C controller */
 	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
@@ -575,7 +575,6 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
 	/* Disable I2C controller */
 	temp = i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
 	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
-	clk_disable_unprepare(i2c_imx->clk);
 }
 
 static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
@@ -894,6 +893,10 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
 
 	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
 
+	result = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
+	if (result < 0)
+		goto out;
+
 	/* Start I2C transfer */
 	result = i2c_imx_start(i2c_imx);
 	if (result)
@@ -950,6 +953,10 @@ fail0:
 	/* Stop I2C transfer */
 	i2c_imx_stop(i2c_imx);
 
+	pm_runtime_mark_last_busy(i2c_imx->adapter.dev.parent);
+	pm_runtime_put_autosuspend(i2c_imx->adapter.dev.parent);
+
+out:
 	dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
 		(result < 0) ? "error" : "success msg",
 			(result < 0) ? result : num);
@@ -1020,9 +1027,10 @@ static int i2c_imx_probe(struct platform_device *pdev)
 
 	ret = clk_prepare_enable(i2c_imx->clk);
 	if (ret) {
-		dev_err(&pdev->dev, "can't enable I2C clock\n");
+		dev_err(&pdev->dev, "can't enable I2C clock, ret=%d\n", ret);
 		return ret;
 	}
+
 	/* Request IRQ */
 	ret = devm_request_irq(&pdev->dev, irq, i2c_imx_isr, 0,
 				pdev->name, i2c_imx);
@@ -1037,6 +1045,18 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	/* Set up adapter data */
 	i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
 
+	/* Set up platform driver data */
+	platform_set_drvdata(pdev, i2c_imx);
+
+	pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
+	ret = pm_runtime_get_sync(&pdev->dev);
+	if (ret < 0)
+		goto rpm_disable;
+
 	/* Set up clock divider */
 	i2c_imx->bitrate = IMX_I2C_BIT_RATE;
 	ret = of_property_read_u32(pdev->dev.of_node,
@@ -1053,12 +1073,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "registration failed\n");
-		goto clk_disable;
+		goto rpm_disable;
 	}
 
-	/* Set up platform driver data */
-	platform_set_drvdata(pdev, i2c_imx);
-	clk_disable_unprepare(i2c_imx->clk);
+	pm_runtime_mark_last_busy(&pdev->dev);
+	pm_runtime_put_autosuspend(&pdev->dev);
 
 	dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", irq);
 	dev_dbg(&i2c_imx->adapter.dev, "device resources: %pR\n", res);
@@ -1071,6 +1090,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
 
 	return 0;   /* Return OK */
 
+rpm_disable:
+	pm_runtime_put_noidle(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+
 clk_disable:
 	clk_disable_unprepare(i2c_imx->clk);
 	return ret;
@@ -1079,6 +1103,11 @@ clk_disable:
 static int i2c_imx_remove(struct platform_device *pdev)
 {
 	struct imx_i2c_struct *i2c_imx = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pm_runtime_get_sync(&pdev->dev);
+	if (ret < 0)
+		return ret;
 
 	/* remove adapter */
 	dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n");
@@ -1093,17 +1122,54 @@ static int i2c_imx_remove(struct platform_device *pdev)
 	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2CR);
 	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2SR);
 
+	clk_disable_unprepare(i2c_imx->clk);
+
+	pm_runtime_put_noidle(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int i2c_imx_runtime_suspend(struct device *dev)
+{
+	struct imx_i2c_struct *i2c_imx  = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(i2c_imx->clk);
+
 	return 0;
 }
 
+static int i2c_imx_runtime_resume(struct device *dev)
+{
+	struct imx_i2c_struct *i2c_imx  = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_prepare_enable(i2c_imx->clk);
+	if (ret)
+		dev_err(dev, "can't enable I2C clock, ret=%d\n", ret);
+
+	return ret;
+}
+
+static const struct dev_pm_ops i2c_imx_pm_ops = {
+	SET_RUNTIME_PM_OPS(i2c_imx_runtime_suspend,
+			   i2c_imx_runtime_resume, NULL)
+};
+#define I2C_IMX_PM_OPS (&i2c_imx_pm_ops)
+#else
+#define I2C_IMX_PM_OPS NULL
+#endif /* CONFIG_PM */
+
 static struct platform_driver i2c_imx_driver = {
 	.probe = i2c_imx_probe,
 	.remove = i2c_imx_remove,
-	.driver	= {
-		.name	= DRIVER_NAME,
+	.driver = {
+		.name = DRIVER_NAME,
+		.pm = I2C_IMX_PM_OPS,
 		.of_match_table = i2c_imx_dt_ids,
 	},
-	.id_table	= imx_i2c_devtype,
+	.id_table = imx_i2c_devtype,
 };
 
 static int __init i2c_adap_imx_init(void)
-- 
1.9.1

RE: [Patch V8] i2c: imx: add runtime pm support to improve the performance

[Gao Pandy]

Ping...
From: Gao Pan <mailto:b54642@freescale.com> Sent: Friday, September 18, 2015 5:51 PM
> To: wsa@the-dreams.de
> Cc: linux-i2c@vger.kernel.org; Li Frank-B20596; Duan Fugang-B38611; Gao
> Pan-B54642; u.kleine-koenig@pengutronix.de; kernel@pengutronix.de;
> hkallweit1@gmail.com
> Subject: [Patch V8] i2c: imx: add runtime pm support to improve the
> performance
> 
> In our former i2c driver, i2c clk is enabled and disabled in xfer
> function, which contributes to power saving. However, the clk enable
> process brings a busy wait delay until the core is stable. As a result,
> the performance is sacrificed.
> 
> To weigh the power consumption and i2c bus performance, runtime pm is the
> good solution for it. The clk is enabled when a i2c transfer starts, and
> disabled after a specifically defined delay.
> 
> Without the patch the test case (many eeprom reads) executes with approx:
> real 1m7.735s
> user 0m0.488s
> sys 0m20.040s
> 
> With the patch the same test case (many eeprom reads) executes with
> approx:
> real 0m54.241s
> user 0m0.440s
> sys 0m5.920s
> 
> Signed-off-by: Fugang Duan <B38611@freescale.com>
> Signed-off-by: Gao Pan <b54642@freescale.com>
> ---
> V2:
> As Uwe Kleine-König's suggestion, the version do below changes:
>  -call clk_prepare_enable in probe to avoid never enabling clock
>   if CONFIG_PM is disabled
>  -enable clock before request IRQ in probe  -remove the pm staff in
> i2c_imx_isr
> 
> V3:
>  -pm_runtime_get_sync returns < 0 as error
> 
> V4:
>  -add pm_runtime_set_active before pm_runtime_enable  -replace
> pm_runtime_put_autosuspend with pm_runtime_autosuspend
>   in probe
>  -add error disposal when i2c_add_numbered_adapter fails
> 
> V5:
>  -clean up and disable runtime PM when i2c_add_numbered_adapter fails  -
> use pm_runtime_get and pm_runtime_put_autosuspend in probe
> 
> V6:
>  -disable the clock manually and set the state to suspended explicitly
> with
>   pm_runtime_set_suspended
> 
> V7:
>  -manually disabling the clock and use pm_runtime_put_noidle in the
> remove callback
> 
> V8:
>  -move out label after the two runtime pm calls in i2c_imx_xfer
> 
>  drivers/i2c/busses/i2c-imx.c | 90
> ++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 78 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 785aa67..91bdf28 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -53,6 +53,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
> +#include <linux/pm_runtime.h>
> 
>  /** Defines
> ********************************************************************
> 
> *************************************************************************
> ******/
> @@ -118,6 +119,8 @@
>  #define I2CR_IEN_OPCODE_0	0x0
>  #define I2CR_IEN_OPCODE_1	I2CR_IEN
> 
> +#define I2C_PM_TIMEOUT		10 /* ms */
> +
>  /** Variables
> ******************************************************************
> 
> *************************************************************************
> ******/
> 
> @@ -520,9 +523,6 @@ static int i2c_imx_start(struct imx_i2c_struct
> *i2c_imx)
> 
>  	i2c_imx_set_clk(i2c_imx);
> 
> -	result = clk_prepare_enable(i2c_imx->clk);
> -	if (result)
> -		return result;
>  	imx_i2c_write_reg(i2c_imx->ifdr, i2c_imx, IMX_I2C_IFDR);
>  	/* Enable I2C controller */
>  	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx,
> IMX_I2C_I2SR); @@ -575,7 +575,6 @@ static void i2c_imx_stop(struct
> imx_i2c_struct *i2c_imx)
>  	/* Disable I2C controller */
>  	temp = i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
>  	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> -	clk_disable_unprepare(i2c_imx->clk);
>  }
> 
>  static irqreturn_t i2c_imx_isr(int irq, void *dev_id) @@ -894,6 +893,10
> @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
> 
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
> 
> +	result = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
> +	if (result < 0)
> +		goto out;
> +
>  	/* Start I2C transfer */
>  	result = i2c_imx_start(i2c_imx);
>  	if (result)
> @@ -950,6 +953,10 @@ fail0:
>  	/* Stop I2C transfer */
>  	i2c_imx_stop(i2c_imx);
> 
> +	pm_runtime_mark_last_busy(i2c_imx->adapter.dev.parent);
> +	pm_runtime_put_autosuspend(i2c_imx->adapter.dev.parent);
> +
> +out:
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
>  		(result < 0) ? "error" : "success msg",
>  			(result < 0) ? result : num);
> @@ -1020,9 +1027,10 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> 
>  	ret = clk_prepare_enable(i2c_imx->clk);
>  	if (ret) {
> -		dev_err(&pdev->dev, "can't enable I2C clock\n");
> +		dev_err(&pdev->dev, "can't enable I2C clock, ret=%d\n", ret);
>  		return ret;
>  	}
> +
>  	/* Request IRQ */
>  	ret = devm_request_irq(&pdev->dev, irq, i2c_imx_isr, 0,
>  				pdev->name, i2c_imx);
> @@ -1037,6 +1045,18 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
>  	/* Set up adapter data */
>  	i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
> 
> +	/* Set up platform driver data */
> +	platform_set_drvdata(pdev, i2c_imx);
> +
> +	pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> +	pm_runtime_use_autosuspend(&pdev->dev);
> +	pm_runtime_set_active(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);
> +
> +	ret = pm_runtime_get_sync(&pdev->dev);
> +	if (ret < 0)
> +		goto rpm_disable;
> +
>  	/* Set up clock divider */
>  	i2c_imx->bitrate = IMX_I2C_BIT_RATE;
>  	ret = of_property_read_u32(pdev->dev.of_node,
> @@ -1053,12 +1073,11 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
>  	ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "registration failed\n");
> -		goto clk_disable;
> +		goto rpm_disable;
>  	}
> 
> -	/* Set up platform driver data */
> -	platform_set_drvdata(pdev, i2c_imx);
> -	clk_disable_unprepare(i2c_imx->clk);
> +	pm_runtime_mark_last_busy(&pdev->dev);
> +	pm_runtime_put_autosuspend(&pdev->dev);
> 
>  	dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", irq);
>  	dev_dbg(&i2c_imx->adapter.dev, "device resources: %pR\n", res); @@
> -1071,6 +1090,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
> 
>  	return 0;   /* Return OK */
> 
> +rpm_disable:
> +	pm_runtime_put_noidle(&pdev->dev);
> +	pm_runtime_disable(&pdev->dev);
> +	pm_runtime_set_suspended(&pdev->dev);
> +
>  clk_disable:
>  	clk_disable_unprepare(i2c_imx->clk);
>  	return ret;
> @@ -1079,6 +1103,11 @@ clk_disable:
>  static int i2c_imx_remove(struct platform_device *pdev)  {
>  	struct imx_i2c_struct *i2c_imx = platform_get_drvdata(pdev);
> +	int ret;
> +
> +	ret = pm_runtime_get_sync(&pdev->dev);
> +	if (ret < 0)
> +		return ret;
> 
>  	/* remove adapter */
>  	dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n"); @@ -1093,17
> +1122,54 @@ static int i2c_imx_remove(struct platform_device *pdev)
>  	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2CR);
>  	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2SR);
> 
> +	clk_disable_unprepare(i2c_imx->clk);
> +
> +	pm_runtime_put_noidle(&pdev->dev);
> +	pm_runtime_disable(&pdev->dev);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int i2c_imx_runtime_suspend(struct device *dev) {
> +	struct imx_i2c_struct *i2c_imx  = dev_get_drvdata(dev);
> +
> +	clk_disable_unprepare(i2c_imx->clk);
> +
>  	return 0;
>  }
> 
> +static int i2c_imx_runtime_resume(struct device *dev) {
> +	struct imx_i2c_struct *i2c_imx  = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = clk_prepare_enable(i2c_imx->clk);
> +	if (ret)
> +		dev_err(dev, "can't enable I2C clock, ret=%d\n", ret);
> +
> +	return ret;
> +}
> +
> +static const struct dev_pm_ops i2c_imx_pm_ops = {
> +	SET_RUNTIME_PM_OPS(i2c_imx_runtime_suspend,
> +			   i2c_imx_runtime_resume, NULL)
> +};
> +#define I2C_IMX_PM_OPS (&i2c_imx_pm_ops) #else #define I2C_IMX_PM_OPS
> +NULL #endif /* CONFIG_PM */
> +
>  static struct platform_driver i2c_imx_driver = {
>  	.probe = i2c_imx_probe,
>  	.remove = i2c_imx_remove,
> -	.driver	= {
> -		.name	= DRIVER_NAME,
> +	.driver = {
> +		.name = DRIVER_NAME,
> +		.pm = I2C_IMX_PM_OPS,
>  		.of_match_table = i2c_imx_dt_ids,
>  	},
> -	.id_table	= imx_i2c_devtype,
> +	.id_table = imx_i2c_devtype,
>  };
> 
>  static int __init i2c_adap_imx_init(void)
> --
> 1.9.1

Re: [Patch V8] i2c: imx: add runtime pm support to improve the performance

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 903 bytes --]

On Fri, Sep 18, 2015 at 05:51:09PM +0800, Gao Pan wrote:
> In our former i2c driver, i2c clk is enabled and disabled in
> xfer function, which contributes to power saving. However,
> the clk enable process brings a busy wait delay until the core
> is stable. As a result, the performance is sacrificed.
> 
> To weigh the power consumption and i2c bus performance, runtime
> pm is the good solution for it. The clk is enabled when a i2c
> transfer starts, and disabled after a specifically defined delay.
> 
> Without the patch the test case (many eeprom reads) executes with approx:
> real 1m7.735s
> user 0m0.488s
> sys 0m20.040s
> 
> With the patch the same test case (many eeprom reads) executes with approx:
> real 0m54.241s
> user 0m0.440s
> sys 0m5.920s
> 
> Signed-off-by: Fugang Duan <B38611@freescale.com>
> Signed-off-by: Gao Pan <b54642@freescale.com>

Uwe? Sascha?


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Re: [Patch V8] i2c: imx: add runtime pm support to improve the performance

[Uwe Kleine-König]

Hello,

On Fri, Sep 18, 2015 at 05:51:09PM +0800, Gao Pan wrote:
> In our former i2c driver, i2c clk is enabled and disabled in
> xfer function, which contributes to power saving. However,
> the clk enable process brings a busy wait delay until the core
> is stable. As a result, the performance is sacrificed.
> 
> To weigh the power consumption and i2c bus performance, runtime
> pm is the good solution for it. The clk is enabled when a i2c
> transfer starts, and disabled after a specifically defined delay.
> 
> Without the patch the test case (many eeprom reads) executes with approx:
> real 1m7.735s
> user 0m0.488s
> sys 0m20.040s
> 
> With the patch the same test case (many eeprom reads) executes with approx:
> real 0m54.241s
> user 0m0.440s
> sys 0m5.920s
> 
> Signed-off-by: Fugang Duan <B38611@freescale.com>
> Signed-off-by: Gao Pan <b54642@freescale.com>

If runtime-pm is disabled the net result of this patch is that the clock
is never disabled, right? I think this is ok, but I would have pointed
that out in the commit log.

> @@ -1037,6 +1045,18 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	/* Set up adapter data */
>  	i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
>  
> +	/* Set up platform driver data */
> +	platform_set_drvdata(pdev, i2c_imx);
> +
> +	pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> +	pm_runtime_use_autosuspend(&pdev->dev);
> +	pm_runtime_set_active(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);
> +
> +	ret = pm_runtime_get_sync(&pdev->dev);
> +	if (ret < 0)
> +		goto rpm_disable;
> +
>  	/* Set up clock divider */
>  	i2c_imx->bitrate = IMX_I2C_BIT_RATE;
>  	ret = of_property_read_u32(pdev->dev.of_node,
> @@ -1053,12 +1073,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "registration failed\n");
> -		goto clk_disable;
> +		goto rpm_disable;

Is it right, that here the same error path is taken as when
pm_runtime_get_sync fails above? Even if it works now, not having the
error cleanup path undo all things in reverse order is a danger to get
it wrong in the next change. So if this is fixable, it would be nice to
implement.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

RE: [Patch V8] i2c: imx: add runtime pm support to improve the performance

[Gao Pandy]

 From: Uwe Kleine-König <mailto:u.kleine-koenig@pengutronix.de> Sent: Tuesday, October 13, 2015 3:07 PM
> To: Gao Pan-B54642
> Cc: wsa@the-dreams.de; linux-i2c@vger.kernel.org; Li Frank-B20596; Duan
> Fugang-B38611; kernel@pengutronix.de; hkallweit1@gmail.com
> Subject: Re: [Patch V8] i2c: imx: add runtime pm support to improve the
> performance
> 
> Hello,
> 
> On Fri, Sep 18, 2015 at 05:51:09PM +0800, Gao Pan wrote:
> > In our former i2c driver, i2c clk is enabled and disabled in xfer
> > function, which contributes to power saving. However, the clk enable
> > process brings a busy wait delay until the core is stable. As a
> > result, the performance is sacrificed.
> >
> > To weigh the power consumption and i2c bus performance, runtime pm is
> > the good solution for it. The clk is enabled when a i2c transfer
> > starts, and disabled after a specifically defined delay.
> >
> > Without the patch the test case (many eeprom reads) executes with
> approx:
> > real 1m7.735s
> > user 0m0.488s
> > sys 0m20.040s
> >
> > With the patch the same test case (many eeprom reads) executes with
> approx:
> > real 0m54.241s
> > user 0m0.440s
> > sys 0m5.920s
> >
> > Signed-off-by: Fugang Duan <B38611@freescale.com>
> > Signed-off-by: Gao Pan <b54642@freescale.com>
> 
> If runtime-pm is disabled the net result of this patch is that the clock
> is never disabled, right? I think this is ok, but I would have pointed
> that out in the commit log.
 
Yes, you are right, I will point that out in the commit log in next version.

> > @@ -1037,6 +1045,18 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> >  	/* Set up adapter data */
> >  	i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
> >
> > +	/* Set up platform driver data */
> > +	platform_set_drvdata(pdev, i2c_imx);
> > +
> > +	pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> > +	pm_runtime_use_autosuspend(&pdev->dev);
> > +	pm_runtime_set_active(&pdev->dev);
> > +	pm_runtime_enable(&pdev->dev);
> > +
> > +	ret = pm_runtime_get_sync(&pdev->dev);
> > +	if (ret < 0)
> > +		goto rpm_disable;
> > +
> >  	/* Set up clock divider */
> >  	i2c_imx->bitrate = IMX_I2C_BIT_RATE;
> >  	ret = of_property_read_u32(pdev->dev.of_node,
> > @@ -1053,12 +1073,11 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> >  	ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
> >  	if (ret < 0) {
> >  		dev_err(&pdev->dev, "registration failed\n");
> > -		goto clk_disable;
> > +		goto rpm_disable;
> 
> Is it right, that here the same error path is taken as when
> pm_runtime_get_sync fails above? Even if it works now, not having the
> error cleanup path undo all things in reverse order is a danger to get it
> wrong in the next change. So if this is fixable, it would be nice to
> implement.
 
When i2c_add_numbered_adapter fails, the cleanup should include the runtime pm stuff. 
So it's ok to take the same error patch.

What do you mean by undo all things in reverse order, I think the cleanup is in reverse order.

The calling sequence is: 
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_set_active(&pdev->dev);
pm_runtime_enable(&pdev->dev);		
pm_runtime_get_sync(&pdev->dev);

The cleanup order is:
pm_runtime_put_noidle(&pdev->dev);
pm_runtime_disable(&pdev->dev);
pm_runtime_set_suspended(&pdev->dev);

Is it that I miss pm_runtime_dont_use_autosuspend(&pdev->dev);

Thank you!

Best Reguards
Gao Pan

Re: [Patch V8] i2c: imx: add runtime pm support to improve the performance

[Shubhrajyoti Datta]

clk_enable is called here.
enables the clock here.
>
> The calling sequence is:
> pm_runtime_use_autosuspend(&pdev->dev);
> pm_runtime_set_active(&pdev->dev);
> pm_runtime_enable(&pdev->dev);
> pm_runtime_get_sync(&pdev->dev);
are we not enabling it again?

there by effectively disabling pm.

Or did I missing something.

>
> The cleanup order is:
> pm_runtime_put_noidle(&pdev->dev);
> pm_runtime_disable(&pdev->dev);
> pm_runtime_set_suspended(&pdev->dev);
>
> Is it that I miss pm_runtime_dont_use_autosuspend(&pdev->dev);
>
> Thank you!
>
> Best Reguards
> Gao Pan
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