From: Heiner Kallweit <mailto:hkallweit1@xxxxxxxxx> Sent: Wednesday, August 26, 2015 3:53 AM > 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 13:09 schrieb Gao Pandy: > > 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. > 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) ��.n��������+%������w��{.n�����{��-��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
