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>
---
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
V5:
-clean up and disable runtime PM when i2c_add_numbered_adapter fails
-use pm_runtime_get and pm_runtime_put_autosuspend in probe
V6:
-disable the clock manually and set the state to suspended explicitly with
pm_runtime_set_suspended
V7:
-manually disabling the clock and use pm_runtime_put_noidle in the remove
callback
drivers/i2c/busses/i2c-imx.c | 90 ++++++++++++++++++++++++++++++++++++++------
1 file changed, 78 insertions(+), 12 deletions(-)
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 785aa67..d7c823b 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 +1045,18 @@ 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);
+
+ ret = pm_runtime_get_sync(&pdev->dev);
+ if (ret < 0)
+ goto rpm_disable;
+
/* Set up clock divider */
i2c_imx->bitrate = IMX_I2C_BIT_RATE;
ret = of_property_read_u32(pdev->dev.of_node,
@@ -1053,12 +1073,11 @@ 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");
- goto clk_disable;
+ goto rpm_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);
@@ -1071,6 +1090,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
return 0; /* Return OK */
+rpm_disable:
+ pm_runtime_put_noidle(&pdev->dev);
+ pm_runtime_disable(&pdev->dev);
+ pm_runtime_set_suspended(&pdev->dev);
+
clk_disable:
clk_disable_unprepare(i2c_imx->clk);
return ret;
@@ -1079,6 +1103,11 @@ 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 +1122,54 @@ 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);
+ clk_disable_unprepare(i2c_imx->clk);
+
+ pm_runtime_put_noidle(&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)
--
1.9.1
--
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