On Thu, Jun 11, 2015 at 7:20 AM, Gao Pan <b54642@xxxxxxxxxxxxx> wrote: > 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 consuption and i2c bus performance, runtime > pm is the good solution for it. The clk is enabled when a i2c > transfer starts, and disabled afer 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. > > Signed-off-by: Fugang Duan <B38611@xxxxxxxxxxxxx> > Signed-off-by: Gao Pan <b54642@xxxxxxxxxxxxx> > --- > drivers/i2c/busses/i2c-imx.c | 78 +++++++++++++++++++++++++++++++++++++------- > 1 file changed, 66 insertions(+), 12 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > index 785aa67..cc4b5d6 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) > @@ -583,6 +582,9 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id) > struct imx_i2c_struct *i2c_imx = dev_id; > unsigned int temp; > > + if (pm_runtime_suspended(i2c_imx->adapter.dev.parent)) > + return IRQ_NONE; > + Didn't quite get this one. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
