On Wed, 20 Aug 2014, atull wrote:
>
>
> On Wed, 20 Aug 2014, Romain Baeriswyl wrote:
>
> > From: Romain Baeriswyl <Romain.Baeriswyl@xxxxxxxxxx>
> >
> > Some legacy devices support ony I2C standard mode at 100kHz.
> > This patch allows to select the standard mode through the DTS
> > with the use of the existing clock-frequency parameter.
> >
> > When clock-frequency parameter is not set, the fast mode is selected.
> > Only when the parameter is set at 100000, the standard mode is selected.
> >
> > Signed-off-by: Romain Baeriswyl <romainba@xxxxxxxxxx>
> > Reviewed-by: Christian Ruppert <christian.ruppert@xxxxxxxxxx>
> > ---
> > drivers/i2c/busses/i2c-designware-platdrv.c | 23 +++++++++++++++++++++--
> > 1 files changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> > index 402ec39..b543fe1 100644
> > --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> > @@ -122,6 +122,7 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > struct i2c_adapter *adap;
> > struct resource *mem;
> > int irq, r;
> > + u32 clk_freq;
> >
> > irq = platform_get_irq(pdev, 0);
> > if (irq < 0) {
> > @@ -151,6 +152,9 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > return PTR_ERR(dev->clk);
> > clk_prepare_enable(dev->clk);
> >
> > + /* fast mode by default because of legacy reasons */
> > + clk_freq = 400000;
> > +
> > if (pdev->dev.of_node) {
> > u32 ht = 0;
> > u32 ic_clk = dev->get_clk_rate_khz(dev);
> > @@ -166,6 +170,17 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > of_property_read_u32(pdev->dev.of_node,
> > "i2c-scl-falling-time-ns",
> > &dev->scl_falling_time);
> > +
> > + of_property_read_u32(pdev->dev.of_node, "clock-frequency",
> > + &clk_freq);
> > +
> > + /* Only standard mode at 100kHz and fast mode at 400kHz
> > + * are supported.
> > + */
> > + if (clk_freq != 100000 && clk_freq != 400000) {
> > + dev_err(&pdev->dev, "Only 100kHz and 400kHz supported");
> > + return -EINVAL;
> > + }
>
> Hi Romain,
>
> It is common to operate i2c at <100KHz on boards that have i2c
> issues. I am using this driver at 50KHz because I have a LCD module
> that just doesn't work at a full 100KHz. Please remove the check for
> these two frequency points.
>
> > }
> >
> > dev->functionality =
> > @@ -175,8 +190,12 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > I2C_FUNC_SMBUS_BYTE_DATA |
> > I2C_FUNC_SMBUS_WORD_DATA |
> > I2C_FUNC_SMBUS_I2C_BLOCK;
> > - dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > - DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
> > + if (clk_freq == 100000)
>
> Please change to <=
>
Hi Romain,
This looks fine to me, my "<= issues" are not important as this isn't
really setting a frequency, but just setting a bit that controls speed.
Acked-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
> > + dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > + DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_STD;
> > + else
> > + dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > + DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
> >
> > /* Try first if we can configure the device from ACPI */
> > r = dw_i2c_acpi_configure(pdev);
> > --
> > 1.7.1
> >
> >
>
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