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From: Gao Pan <b54...@freescale.com> Sent: Thursday, June 18, 2015 5:28 PM
> To: w...@the-dreams.de
> Cc: linux-i2c@vger.kernel.org; Li Frank-B20596; Duan Fugang-B38611;
> Gao Pan-B54642; u.kleine-koe...@pengutronix.de
> Subject: [Patch v2] i2c: imx: add runtime pm support to improve the
> performance
>
> 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
>
> From the test result, the patch get better performance.
>
> 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
>
> Signed-off-by: Fugang Duan <b38...@freescale.com>
> Signed-off-by: Gao Pan <b54...@freescale.com>
> ---
> drivers/i2c/busses/i2c-imx.c | 76
> +++++++++++++++++++++++++++++++++++++-
> ------
> 1 file changed, 65 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c
> b/drivers/i2c/busses/i2c-imx.c index 785aa67..37cd9f6 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 (IS_ERR_VALUE(result))
> + 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 +1045,13 @@ 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_enable(&pdev->dev);
> + pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> + pm_runtime_use_autosuspend(&pdev->dev);
> +
> /* Set up clock divider */
> i2c_imx->bitrate = IMX_I2C_BIT_RATE;
> ret = of_property_read_u32(pdev->dev.of_node,
> @@ -1056,9 +1071,8 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> 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_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); @@
> -1079,6 +1093,11 @@ 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 (IS_ERR_VALUE(ret))
> + return ret;
>
> /* remove adapter */
> dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n"); @@ -1093,14
> +1112,49 @@ 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 = {
> + .probe = i2c_imx_probe,
> + .remove = i2c_imx_remove,
> + .driver = {
> .name = DRIVER_NAME,
> + .pm = I2C_IMX_PM_OPS,
> .of_match_table = i2c_imx_dt_ids,
> },
> .id_table = imx_i2c_devtype,
> --
> 1.9.1
