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 <=
> + 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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