Hi Mika,

On 12/16/2015 03:42 AM, Mika Westerberg wrote:
+Jarkko and Andy

On Tue, Dec 15, 2015 at 04:38:58PM -0600, Suravee Suthikulpanit wrote:
The current driver uses input clock source frequency to calculate
values for [SS|FS]_[HC|LC] registers. However, when booting ACPI, we do not
currently have a good way to provide the frequency information.
Instead, we can leverage the SSCN and FFCN ACPI methods, which can be used
to directly provide these values.

So, this patch removes the clock requirement when SSCN and FFCN
are provided.

Actually I think the only thing you need to change is i2c_dw_init() so
that it does not call dev->get_clk_rate_khz(dev) if *CNT values are
already provided.

Please see below.


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.

Thanks,
Suravee
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