CVS commit: src/sys/dev/acpi

["Jared D. McNeill" <jmcneill%netbsd.org@localhost>]

Module Name:    src
Committed By:   jmcneill
Date:           Sat Jan 15 14:49:43 UTC 2022

Modified Files:
        src/sys/dev/acpi: sdhc_acpi.c

Log Message:
acpi: sdhc: Add support for RK356x eMMC controller.

RK356x has a DesignWare eMMC controller that is somewhat SDHCI compliant,
with one major problem -- the clock divisor doesn't actually work. To
change the clock card on Rockchip SoCs, the clock frequency needs to be
adjusted in the Clock & Reset Unit (CRU) directly.

The RK356x UEFI implementation introduces a DSM that allows drivers to
request firmware assistance in setting the card clock rate, for instances
like this where the divisor is broken.

>From the UEFI README:

  Function 1: Set Card Clock

  The _DSM control method parameters for the Set Card Clock function are
  as follows:

  Arguments

   * Arg0: UUID = 434addb0-8ff3-49d5-a724-95844b79ad1f
   * Arg1: Revision = 0
   * Arg2: Function Index = 1
   * Arg3: Target card clock rate in Hz.

  Return

   The actual card clock rate in Hz. Will be less than or equal to the
   target clock rate. Returns 0 if the target clock rate could not be set.


To generate a diff of this commit:
cvs rdiff -u -r1.16 -r1.17 src/sys/dev/acpi/sdhc_acpi.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.