On Mon, 2017-04-10 at 17:49 +0200, Hans de Goede wrote:
> Several cherrytrail devices (all of which ship with windows 10) hide
> the
> lpss pwm controller in ACPI, typically the _STA method looks like
> this:
CherryTrail
PWM
LPSS
>
> Method (_STA, 0, NotSerialized) // _STA: Status
> {
> If (OSID == One)
> {
> Return (Zero)
> }
>
> Return (0x0F)
> }
>
> Where OSID is some dark magic seen in all cherrytrail 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 use it when it needs it),
> this
> commit makes acpi_bus_get_status() always set status to
> ACPI_STA_DEFAULT
> for the 80862288 device, fixing the lack of backlight control.
> +#ifdef CONFIG_X86
> +/*
> + * Some ACPI devices are hidden (status == 0x0) in recent BIOS-es
> because
> + * some recent windows drivers bind to one device but poke at
> multiple
Windows
> + * devices at the same time, so the others get hidden.
> + * We work around this by always reporting ACPI_STA_DEFAULT for these
> + * devices. Note this MUST only be done for devices where this is
> safe.
> + *
> + * This forcing of devices to be present is limited to specific CPU
> (SoC)
> + * models both to avoid potentially causing trouble on other models
> and
> + * because some HIDs are re-used on different SoCs for completely
> + * different devices.
> + */
> +struct always_present_device_id {
> + struct acpi_device_id hid[2];
> + struct x86_cpu_id cpu_id[2];
> +};
> +
> +#define ENTRY(hid, cpu_model) {
> \
> + { { hid, }, {} },
> \
> + { { X86_VENDOR_INTEL, 6, cpu_model, X86_FEATURE_ANY, }, {} },
> \
Can we use separate macro for this. i.e. ICPU() ?
Perhaps at some point we might switch to set of generic ICPU()-like
macros.
Moreover, it seems you may change it to use only one existing structure
ICPU(model, hid)
> +}
> +
> +static const struct always_present_device_id
> always_present_device_ids[] = {
> + /*
> + * Cherrytrail pwm directly poked by GPU driver in win10,
> + * but Linux uses a separate pwm driver, harmless if not
> used.
> + */
> + ENTRY("80862288", INTEL_FAM6_ATOM_AIRMONT),
> +};
> +#endif
> +
> +void acpi_set_device_status(struct acpi_device *adev, u32 sta)
> +{
> + u32 *status = (u32 *)&adev->status;
> +#ifdef CONFIG_X86
> + int i;
> +
> + /* acpi_match_device_ids checks status, so start with default
> */
> + *status = ACPI_STA_DEFAULT;
> + for (i = 0; i < ARRAY_SIZE(always_present_device_ids); i++) {
> + if (acpi_match_device_ids(adev,
> + always_present_device_ids[i].hid) == 0 &&
> + x86_match_cpu(always_present_device_ids[i].cpu_id
> )) {
I don't like this. It looks a bit hackish. If we need more, than one hid
per CPU, we might just supply an array
ICPU(model, hids)
> + dev_info(&adev->dev, "Device [%s] is in
> always present list setting status [%08x]\n",
> + adev->pnp.bus_id, ACPI_STA_DEFAULT);
> + return;
> + }
> + }
> +#endif
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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