By using a module parameter named acpi.supported_rev=<value>, the BIOS may be told a different supported ACPI revision compared to the default (which currently is 5, but will be modified to 2 when the revert of b1ef29725865 is reverted).
Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net --- Documentation/kernel-parameters.txt | 14 ++++++++++++++ drivers/acpi/osl.c | 16 ++++++++++++++++ 2 files changed, 30 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 61ab162..75f1f8e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -335,6 +335,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. to assume that this machine's pmtimer latches its value and always returns good values.
+ acpi.rev= [HW,ACPI] + Tell ACPI BIOS the supported ACPI REV + Format: <int> in range 0..5 + Up to and including Linux v4.1, the BIOS was told which + ACPI revision the ACPICA subsystem in Linux actually + supports (which was 5 at the time); from v4.2 on, this + value will be set statically to 2 to match the behavior + of other ACPI implementations. As some BIOS may operate + differently depending on which value _REV is set to, this + parameter offers the capability to specify what to export + to the BIOS. Note that such changes in the behavior of + the BIOS may only be visible after cold booting the + system with this parameter _twice_. + acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low }
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index db14a66..caa52f7 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -538,6 +538,11 @@ acpi_os_get_physical_address(void *virt, acpi_physical_address * phys)
static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN];
+/* acpi_supported_rev is 0 in case of no override; overrides are limited to + * values between 1 to 5. To simplify casting, use an unsigned long */ +static unsigned long acpi_supported_rev; +module_param_named(rev, acpi_supported_rev, ulong, 0); + acpi_status acpi_os_predefined_override(const struct acpi_predefined_names *init_val, char **new_val) @@ -552,6 +557,17 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val, *new_val = acpi_os_name; }
+ if (!memcmp(init_val->name, "_REV", 4) && (acpi_supported_rev > 0)) { + if (acpi_supported_rev <= 5) { + printk(KERN_INFO PREFIX + "Overriding _REV definition to %lu\n", + acpi_supported_rev); + *new_val = (char *) acpi_supported_rev; + } else + printk(KERN_INFO PREFIX + "_REV override must be between 1 to 5"); + } + return AE_OK; }