On 12/16/2015 08:28 AM, Mika Westerberg wrote:
On Wed, Dec 16, 2015 at 08:11:12AM -0600, Suravee Suthikulpanit wrote:
The clk framework should work fine if the returned clock is NULL (which
I think is your case).

The driver gates clocks when the device is suspended and on Intel LPSS
there actually is a clock that gets gated.

[..]
@@ -203,13 +223,11 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
                dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
                        DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;

-       dev->clk = devm_clk_get(&pdev->dev, NULL);
-       dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
-       if (IS_ERR(dev->clk))
-               return PTR_ERR(dev->clk);

Actually, if we don't provide the clock (which is the case for ACPI), this
would also return and cause the probing to fail.

Indeed it seems that when you have CONFIG_COMMON_CLK selected the clock
framework starts returning errors if the clock is not found.

Since we need the clock for Intel LPSS I2C host controllers (and they
may have *CNT methods), I think you just need to provide the clock for
AMD I2C host controller in similar way than we do in
drivers/acpi/acpi_lpss.c.

I am trying to avoid having to hard-coded clock frequency value in the driver. Would it be alright to not return w/ error, and just do the following?

        dev->clk = devm_clk_get(&pdev->dev, NULL);
        if (!IS_ERR(dev->clk))
                dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;

This should work for the Intel case when clock is also provided.

Thanks,
Suravee
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