> -----Original Message----- > From: Fugang Duan [mailto:b38611@xxxxxxxxxxxxx] > Sent: Monday, May 19, 2014 9:22 PM > To: wsa@xxxxxxxxxxxxx > Cc: linux-i2c@xxxxxxxxxxxxxxx; u.kleine-koenig@xxxxxxxxxxxxxx; Duan > Fugang-B38611; Li Frank-B20596 > Subject: [PATCH] i2c: imx: update i2c clock divider for each transaction > > Since IMX serial SOCs support low bus freq mode, some clocks freq may > change to save power. I2C needs to check the clock source and update the > divider. > > For example: > i.MX6SL I2C clk is from IPG_PERCLK which is sourced from IPG_CLK. > Under normal operation, IPG_CLK is 66MHz, ipg_perclk is at 22MHz. > In low bus freq mode, IPG_CLK is at 12MHz and IPG_PERCLK is down to 4MHz. > So the I2C driver must update the divider register for each transaction > when the current IPG_PERCLK is not equal to the clock of previous > transaction. > > Signed-off-by: Fugang Duan <B38611@xxxxxxxxxxxxx> Acked by: Frank Li<frank.li@xxxxxxxxxxxxx> > --- > drivers/i2c/busses/i2c-imx.c | 94 ++++++++++++++++++++++--------------- > ---- > 1 files changed, 50 insertions(+), 44 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > index 6c2ac05..2fdff4d 100644 > --- a/drivers/i2c/busses/i2c-imx.c > +++ b/drivers/i2c/busses/i2c-imx.c > @@ -183,6 +183,8 @@ struct imx_i2c_struct { > unsigned int disable_delay; > int stopped; > unsigned int ifdr; /* IMX_I2C_IFDR */ > + unsigned int cur_clk; > + unsigned int bitrate; > const struct imx_i2c_hwdata *hwdata; > }; > > @@ -305,6 +307,49 @@ static int i2c_imx_acked(struct imx_i2c_struct > *i2c_imx) > return 0; > } > > +static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx) { > + struct imx_i2c_clk_pair *i2c_clk_div = i2c_imx->hwdata->clk_div; > + unsigned int i2c_clk_rate; > + unsigned int div; > + int i; > + > + /* Divider value calculation */ > + i2c_clk_rate = clk_get_rate(i2c_imx->clk); > + if (i2c_imx->cur_clk == i2c_clk_rate) > + return; > + else > + i2c_imx->cur_clk = i2c_clk_rate; > + > + div = (i2c_clk_rate + i2c_imx->bitrate - 1) / i2c_imx->bitrate; > + if (div < i2c_clk_div[0].div) > + i = 0; > + else if (div > i2c_clk_div[i2c_imx->hwdata->ndivs - 1].div) > + i = i2c_imx->hwdata->ndivs - 1; > + else > + for (i = 0; i2c_clk_div[i].div < div; i++); > + > + /* Store divider value */ > + i2c_imx->ifdr = i2c_clk_div[i].val; > + > + /* > + * There dummy delay is calculated. > + * It should be about one I2C clock period long. > + * This delay is used in I2C bus disable function > + * to fix chip hardware bug. > + */ > + i2c_imx->disable_delay = (500000U * i2c_clk_div[i].div > + + (i2c_clk_rate / 2) - 1) / (i2c_clk_rate / 2); > + > + /* dev_dbg() can't be used, because adapter is not yet registered */ > +#ifdef CONFIG_I2C_DEBUG_BUS > + dev_dbg(&i2c_imx->adapter.dev, "<%s> I2C_CLK=%d, REQ DIV=%d\n", > + __func__, i2c_clk_rate, div); > + dev_dbg(&i2c_imx->adapter.dev, "<%s> IFDR[IC]=0x%x, REAL DIV=%d\n", > + __func__, i2c_clk_div[i].val, i2c_clk_div[i].div); #endif } > + > static int i2c_imx_start(struct imx_i2c_struct *i2c_imx) { > unsigned int temp = 0; > @@ -312,6 +357,8 @@ static int i2c_imx_start(struct imx_i2c_struct > *i2c_imx) > > dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__); > > + i2c_imx_set_clk(i2c_imx); > + > result = clk_prepare_enable(i2c_imx->clk); > if (result) > return result; > @@ -367,45 +414,6 @@ static void i2c_imx_stop(struct imx_i2c_struct > *i2c_imx) > clk_disable_unprepare(i2c_imx->clk); > } > > -static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx, > - unsigned int rate) > -{ > - struct imx_i2c_clk_pair *i2c_clk_div = i2c_imx->hwdata->clk_div; > - unsigned int i2c_clk_rate; > - unsigned int div; > - int i; > - > - /* Divider value calculation */ > - i2c_clk_rate = clk_get_rate(i2c_imx->clk); > - div = (i2c_clk_rate + rate - 1) / rate; > - if (div < i2c_clk_div[0].div) > - i = 0; > - else if (div > i2c_clk_div[i2c_imx->hwdata->ndivs - 1].div) > - i = i2c_imx->hwdata->ndivs - 1; > - else > - for (i = 0; i2c_clk_div[i].div < div; i++); > - > - /* Store divider value */ > - i2c_imx->ifdr = i2c_clk_div[i].val; > - > - /* > - * There dummy delay is calculated. > - * It should be about one I2C clock period long. > - * This delay is used in I2C bus disable function > - * to fix chip hardware bug. > - */ > - i2c_imx->disable_delay = (500000U * i2c_clk_div[i].div > - + (i2c_clk_rate / 2) - 1) / (i2c_clk_rate / 2); > - > - /* dev_dbg() can't be used, because adapter is not yet registered */ > -#ifdef CONFIG_I2C_DEBUG_BUS > - dev_dbg(&i2c_imx->adapter.dev, "<%s> I2C_CLK=%d, REQ DIV=%d\n", > - __func__, i2c_clk_rate, div); > - dev_dbg(&i2c_imx->adapter.dev, "<%s> IFDR[IC]=0x%x, REAL DIV=%d\n", > - __func__, i2c_clk_div[i].val, i2c_clk_div[i].div); > -#endif > -} > - > static irqreturn_t i2c_imx_isr(int irq, void *dev_id) { > struct imx_i2c_struct *i2c_imx = dev_id; @@ -619,7 +627,6 @@ static > int i2c_imx_probe(struct platform_device *pdev) > struct imxi2c_platform_data *pdata = dev_get_platdata(&pdev->dev); > void __iomem *base; > int irq, ret; > - u32 bitrate; > > dev_dbg(&pdev->dev, "<%s>\n", __func__); > > @@ -683,12 +690,11 @@ static int i2c_imx_probe(struct platform_device > *pdev) > i2c_set_adapdata(&i2c_imx->adapter, i2c_imx); > > /* Set up clock divider */ > - bitrate = IMX_I2C_BIT_RATE; > + i2c_imx->bitrate = IMX_I2C_BIT_RATE; > ret = of_property_read_u32(pdev->dev.of_node, > - "clock-frequency", &bitrate); > + "clock-frequency", &i2c_imx->bitrate); > if (ret < 0 && pdata && pdata->bitrate) > - bitrate = pdata->bitrate; > - i2c_imx_set_clk(i2c_imx, bitrate); > + i2c_imx->bitrate = pdata->bitrate; > > /* Set up chip registers to defaults */ > imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN, > -- > 1.7.8 -- 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
