On 12/15/2015 07:27 AM, Mika Westerberg wrote:
On Mon, Dec 14, 2015 at 06:53:25PM -0600, Suravee Suthikulanit wrote:
>I'm not sure if this has been discussed earlier. But after looking at the
>the acpi_apd driver, all we need is just the platform-specific input clock
>frequency value used by the drivers/i2c/busses/i2c-designware-core.c:
>i2c_dw_init() to calculate the values to program into the DW_IC_SS_SCL_HCNT
>and DW_IC_SS_SCL_LCNT registers.
There is a way to pass *CNT values already from ACPI to the driver -- It
looks for method called FMCN (or SSCN) and retrieves the values from
there if found.

Right, I also noticed this afterward. By the way, are FMCN and SSCN documented anywhere in the ACPI spec? I am trying to figure out how to update the ACPI table to add this information for the AMD Seattle (ARM64) platform, and I will also submit a patch to add the new HID for this driver.

The driver could be modified not to require clock if it already knows
*CNT values.

Sounds good.

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