From: Heiner Kallweit <mailto:hkallwe...@gmail.com> Sent: Thursday, August 27,
2015 2:52 AM
> 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 V5] i2c: imx: add runtime pm support to improve the
> performance
>
> Am 26.08.2015 um 07:23 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
> >
> > V5:
> > -clean up and disable runtime PM when i2c_add_numbered_adapter fails
> > -use pm_runtime_get and pm_runtime_put_autosuspend in probe
> >
> > drivers/i2c/busses/i2c-imx.c | 91
> > ++++++++++++++++++++++++++++++++++++--------
> > 1 file changed, 76 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx.c
> > b/drivers/i2c/busses/i2c-imx.c index 785aa67..8940a89 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);
> > @@ -1020,15 +1027,17 @@ 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);
> > if (ret) {
> > dev_err(&pdev->dev, "can't claim irq %d\n", irq);
> > - goto clk_disable;
> > + clk_disable_unprepare(i2c_imx->clk);
> > + return ret;
> > }
> >
> > /* Init queue */
> > @@ -1037,6 +1046,18 @@ 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(&pdev->dev);
> > + if (ret < 0)
> > + return ret;
> > +
> > /* Set up clock divider */
> > i2c_imx->bitrate = IMX_I2C_BIT_RATE;
> > ret = of_property_read_u32(pdev->dev.of_node,
> > @@ -1053,12 +1074,11 @@ 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); @@
> > -1071,14 +1091,20 @@ static int i2c_imx_probe(struct platform_device
> > *pdev)
> >
> > return 0; /* Return OK */
> >
> > -clk_disable:
> > - clk_disable_unprepare(i2c_imx->clk);
> > +rpm_disable:
> > + pm_runtime_put(&pdev->dev);
> > + pm_runtime_disable(&pdev->dev);
> The cleanup has to be in reverse order of the setup. Therefore the rpm
> cleanup should happen before the clock disabling.
> As it is now you wouldn't disable the clock when registration fails.
Thanks. When registration fails, pm_runtime_put is used to cleanup the runtime
status and disable clk.
Actually, I think pm_runtime_put_sync_suspend is better here.
> And better use pm_runtime_put_noidle. You don't want to suspend here if
> the ref count is 0.
>
> Last but not least a call to pm_runtime_set_suspended is missing (because
> after disabling the clock the device effectively is in suspended state).
The status is set suspended in pm_runtime_put_sync_suspend, so
pm_runtime_set_suspended is unnecessary here.
What do you think about it?
Please see the following code:
rpm_disable:
pm_runtime_put_sync_suspend(&pdev->dev);
pm_runtime_disable(&pdev->dev);
return ret;
> > return ret;
> > }
> >
> > 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
> > +1119,52 @@ 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)
> >
