From: Heiner Kallweit <mailto:hkallwe...@gmail.com> Sent: Wednesday, August 26,
2015 3:53 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 V4] i2c: imx: add runtime pm support to improve the
> performance
>
> Am 25.08.2015 um 13:09 schrieb Gao Pandy:
> > 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.
> No, it won't. This function checks whether the device is in state
> "active" and in this case it doesn't call the resume callback and returns
> 1. See also the source code of runtime PM in drivers/base/power/runtime.c
Thank you, will change it in next version.
> Rgds, Heiner
> >
> >> 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)
