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| Code Block |
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CLK:
Method(GCLK, ...) // Get Clock Rate
Method(SCLK, ...) // Set Clock Rate
DEV:
_PRS:
ClockInput(FREQ_1, 1, MHz, Variable, CLK,)
ClockInput(FREQ_2, 1, MHz, Variable, CLK, )
ClockInput(FREQ_3, 1, MHz, Variable, CLK, )
_CRS:
freq_num, freq_div = CLK.GCLK(...)
ClockInput(freq_num, freq_div, ... , Variable, "//SB.CLK", )
_SRS:
...
local0 = decode(Arg0)
CLK.SCLK(local0)
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Challenges
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ClockInput resource doesn't have resource names so we cannot index them for modification.
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Linux Design
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Option 1: Devices directly use the ACPI resources to get the list of possible clock rates and select.
Option 2: Add an ACPI-clk device to the clock framework that uses the clock resources to get and set rates.
ACPICA
Patch to add ClockInput resource support in ACPICA
https://github.com/nsait-linaro/acpica/commit/c9ca60aa5a5ccd9fe4e71124101744d8ed12a64e