On Fri, 2017-04-21 at 12:47 +0200, Hans de Goede wrote:
> Several Bay / Cherry Trail devices (all of which ship with Windows 10)
> hide
> the LPSS PWM controller in ACPI, typically the _STA method looks like
> this:
>
> Method (_STA, 0, NotSerialized) // _STA: Status
> {
> If (OSID == One)
> {
> Return (Zero)
> }
>
> Return (0x0F)
> }
>
> Where OSID is some dark magic seen in all Cherry Trail ACPI tables
> making
> the machine behave differently depending on which OS it *thinks* it is
> booting, this gets set in a number of ways which we cannot control, on
> some newer machines it simple hardcoded to "One" aka win10.
>
> This causes the PWM controller to get hidden, which means Linux cannot
> control the backlight level on cht based tablets / laptops.
>
> Since loading the driver for this does no harm (the only in kernel
> user
> of it is the i915 driver, which will only uses it when it needs it),
> this
> commit makes acpi_bus_get_status() always set status to
> ACPI_STA_DEFAULT
> for the LPSS PWM device, fixing the lack of backlight control.
>
> drivers/acpi/Makefile | 1 +
> drivers/acpi/bus.c | 5 +++
> drivers/acpi/x86/x86_utils.c | 85
> ++++++++++++++++++++++++++++++++++++++++++++
Perhaps .../x86/utils.c ?
> include/acpi/acpi_bus.h | 9 +++++
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index 34fbe02..784bda6 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -114,6 +114,11 @@ int acpi_bus_get_status(struct acpi_device
> *device)
> acpi_status status;
> unsigned long long sta;
>
> + if (acpi_device_always_present(device)) {
> + acpi_set_device_status(device, ACPI_STA_DEFAULT);
> + return 0;
> + }
> +
> status = acpi_bus_get_status_handle(device->handle, &sta);
> if (ACPI_FAILURE(status))
> return -ENODEV;
>
> +#define ICPU(model) { X86_VENDOR_INTEL, 6, model,
> X86_FEATURE_ANY, }
> +
> +#define ENTRY(hid, uid, cpu_models) {
cpu_models -> cpu_model ?
Or I missed that it's an array?
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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