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 <[email protected]>
> Signed-off-by: Gao Pan <[email protected]>
> [wsa: fixed some indentation]
> Signed-off-by: Wolfram Sang <[email protected]>
> ---
> 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.
> 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.
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)
>
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