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soc/intel/common/block/acpi: Return existing Object for _DSM subfunction 

Currently the LPIT Get Constraints _DSM subfunction returns a package
containing the path to a nonexistent device (\NULL). This is used to
work around an issue with Windows, where returning an empty package will
cause a BSOD.  However, using this non-existent device can also cause
confusion, as on Linux, it shows an error in dmesg, e.g.

    ACPI Error: AE_NOT_FOUND, While resolving a named reference package
    element - \NULL (20200925/dspkginit-438)

Therefore, this patch modifies this returned package slightly to include
the path to ACPI_CPU_STRING for CPU 0, which should always be emitted on
Intel platforms that use the PEP driver.

Tested on google/brya0 on ChromeOS 5.10 kernel
Tested with current Windows 11 ISO

Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Change-Id: If74a1620ff0de33bcdba06e1225c5e28c64253e1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61868
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Shobhit Srivastava <shobhit.srivastava@intel.corp-partner.google.com>
This commit is contained in:
Tim Wawrzynczak 2022-02-11 09:46:15 -07:00
parent b4ba289fa5
commit 7a94ad720e
1 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/soc/intel/common/block/acpi/pep.c
View File

@ -70,15 +70,19 @@ static void read_pmc_lpm_requirements(const struct soc_pmc_lpm *lpm,
} }
/* /*
* For now there is only one disabled non-existent device, because Windows * Windows expects a non-empty package for this subfunction, otherwise it
* expects at least one device and crashes without it with a bluescreen * results in a bluescreen (`INTERNAL_POWER_ERROR`); returning an empty package
* (`INTERNAL_POWER_ERROR`). Returning an empty package does not work. * does not work. To workaround this, return a package describing a single
* device, one that is known to exist, i.e. ACPI_CPU_STRING. expects at least
* one device and crashes without it with a bluescreen.
*/ */
static void lpi_get_constraints(void *unused) static void lpi_get_constraints(void *unused)
{ {
char path[16];
/* /*
* Return (Package() { * Return (Package() {
* Package() { "\NULL", 0, * Package() { "\_SB.CP00", 0,
* Package() { 0, * Package() { 0,
* Package() { 0xff, 0 }}}}) * Package() { 0xff, 0 }}}})
*/ */
@ -87,7 +91,8 @@ static void lpi_get_constraints(void *unused)
{ {
acpigen_write_package(3); acpigen_write_package(3);
{ {
acpigen_emit_namestring("\\NULL"); snprintf(path, sizeof(path), CONFIG_ACPI_CPU_STRING, 0);
acpigen_emit_namestring(path);
acpigen_write_integer(0); /* device disabled */ acpigen_write_integer(0); /* device disabled */
acpigen_write_package(2); acpigen_write_package(2);
{ {