From: Heiner Kallweit <mailto:hkallweit1@xxxxxxxxx> Sent: Tuesday, August 25, 2015 2:37 PM > To: Gao Pan-B54642; wsa@xxxxxxxxxxxxx > Cc: linux-i2c@xxxxxxxxxxxxxxx; Li Frank-B20596; Duan Fugang-B38611; > u.kleine-koenig@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx > 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 <B38611@xxxxxxxxxxxxx> > > Signed-off-by: Gao Pan <b54642@xxxxxxxxxxxxx> > > [wsa: fixed some indentation] > > Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx> > > --- > > 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) > > ��.n��������+%������w��{.n�����{��-��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
