> From: linux-i2c-ow...@vger.kernel.org [mailto:linux-i2c-
> ow...@vger.kernel.org] On Behalf Of Gao Pandy
> Sent: Tuesday, August 25, 2015 7:09 PM
> To: Heiner Kallweit; w...@the-dreams.de
> Cc: linux-i2c@vger.kernel.org; Li Frank-B20596; Duan Fugang-B38611;
> u.kleine-koe...@pengutronix.de; ker...@pengutronix.de
> Subject: RE: [Patch V4] i2c: imx: add runtime pm support to improve the
> performance
>
> From: Heiner Kallweit <mailto:hkallwe...@gmail.com> Sent: Tuesday, August
> 25, 2015 2:37 PM
> > To: Gao Pan-B54642; w...@the-dreams.de
> > Cc: linux-i2c@vger.kernel.org; Li Frank-B20596; Duan Fugang-B38611;
> > u.kleine-koe...@pengutronix.de; ker...@pengutronix.de
> > Subject: Re: [Patch V4] i2c: imx: add runtime pm support to improve
> > the performance
> >
> > Am 25.08.2015 um 04:20 schrieb 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 <b38...@freescale.com>
> > > Signed-off-by: Gao Pan <b54...@freescale.com>
> > > [wsa: fixed some indentation]
> > > Signed-off-by: Wolfram Sang <w...@the-dreams.de>
> > > ---
> > > 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
> > >
> > > drivers/i2c/busses/i2c-imx.c | 79
> > > ++++++++++++++++++++++++++++++++++++++------
> > > 1 file changed, 68 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-imx.c
> > > b/drivers/i2c/busses/i2c-imx.c index 785aa67..7c63047 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);
> > >
> > > +out:
> > > + pm_runtime_mark_last_busy(i2c_imx->adapter.dev.parent);
> > > + pm_runtime_put_autosuspend(i2c_imx->adapter.dev.parent);
> > > +
> > > 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 +1045,14 @@ 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);
> > > +
> > > /* Set up clock divider */
> > > i2c_imx->bitrate = IMX_I2C_BIT_RATE;
> > > ret = of_property_read_u32(pdev->dev.of_node,
> > > @@ -1053,12 +1069,13 @@ 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");
> > > + pm_runtime_mark_last_busy(&pdev->dev);
> > > + pm_runtime_autosuspend(&pdev->dev);
> > It would be more consistent with the general practice not to clean up
> > here but to define a new error label, goto there and do the clean-up
> > there.
> > And if adding the adapter fails most likely you don't want to
> > autosuspend but clean up and disable runtime PM.
>
> Thank you, will change it in next version.
>
> > > goto clk_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_autosuspend(&pdev->dev);
> > >From enabling runtime PM to here you don't hold a reference so
> > >theoretically
> > it might happen that the device gets suspended in-between.
> > I'm not able to say whether this is an actual potential issue here.
> > However to be on the safe side it wouldn't hurt to do a
> > pm_runtime_get_xx when enabling PM and use pm_runtime_put_autosuspend
> here.
>
> Thanks. If I use pm_runtime_get_xx when enabling PM, clk_prepare_enable
> will be called again.
> However, it has been called before. It's kind of code redundancy to use
> pm_runtime_get_xx.
>
> > Regards, Heiner
> > >
> > > dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", irq);
> > > dev_dbg(&i2c_imx->adapter.dev, "device resources: %pR\n", res); @@
> > > -1079,6 +1096,11 @@ 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
> > > +1115,52 @@ 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);
> > >
> > > + pm_runtime_put_sync(&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)
