On Tue, Apr 18, 2017 at 1:54 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> Several 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 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.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> Changes in v2:
> -Use pr_debug instead of ACPI_DEBUG_PRINT
> Changes in v3:
> -Un-inline acpi_set_device_status and do the always_present_device_ids
> table check inside the un-inlined version of it
> Changes in v4:
> -Use dev_info instead of pr_debug
> -Not only check for ACPI HID but also for CPU (SoC) model so as to not
> for devices present on other models then for which the quirk is intended and
> to avoid enabling unrelated ACPI devices which happen to use the same HID
> Changes in v5:
> -Only do the dev_info once per device (acpi_set_device_status gets called
> multiple times per device during boot)
> Changes in v6:
> -Allow specifying more then one CPU-model for a single HID
> -Not only match the HID but also the UID, like on Cherry Trail, on some Bay
> Trail Windows 10 tablets we need to enable the PWM controller to get working
> backlight even though _STA returns 0. The Bay Trail SoC has 2 PWM controllers
> and we only need the first one. UID matching will allows adding an entry for
> Bay Trail which only enables the first PWM controller
> ---
> drivers/acpi/bus.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
> include/acpi/acpi_bus.h | 6 +----
> 2 files changed, 66 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index 34fbe02..eb30630 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -34,6 +34,8 @@
> #include <linux/reboot.h>
> #include <linux/delay.h>
> #ifdef CONFIG_X86
> +#include <asm/cpu_device_id.h>
> +#include <asm/intel-family.h>
> #include <asm/mpspec.h>
> #endif
> #include <linux/acpi_iort.h>
> @@ -132,6 +134,69 @@ int acpi_bus_get_status(struct acpi_device *device)
> }
> EXPORT_SYMBOL(acpi_bus_get_status);
>
> +#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
> + * 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_ids[2];
This really is x86-specific, so it should go into somewhere like
arch/x86/kernel/acpi/ or drivers/acpi/x86/ (not present yet).
> + const char *uid;
> +};
> +
> +#define ICPU(model) { X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, }
> +
> +#define ENTRY(hid, uid, cpu_models) { \
> + { { hid, }, {} }, \
> + { cpu_models, {} }, \
> + uid, \
> +}
> +
> +static const struct always_present_device_id always_present_device_ids[] = {
> + /*
> + * Cherry Trail PWM directly poked by GPU driver in win10,
> + * but Linux uses a separate PWM driver, harmless if not used.
> + */
> + ENTRY("80862288", "1", ICPU(INTEL_FAM6_ATOM_AIRMONT)),
> +};
> +#endif
> +
> +void acpi_set_device_status(struct acpi_device *adev, u32 sta)
> +{
> + u32 *status = (u32 *)&adev->status;
> +#ifdef CONFIG_X86
> + u32 old_status = *status;
> + 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 &&
> + adev->pnp.unique_id &&
> + strcmp(adev->pnp.unique_id,
> + always_present_device_ids[i].uid) == 0 &&
> + x86_match_cpu(always_present_device_ids[i].cpu_ids)) {
Split this condition please. It is almost unreadable as is.
> + if (old_status != ACPI_STA_DEFAULT)
> + dev_info(&adev->dev,
> + "Device [%s] is in always present list setting status [%08x]\n",
> + adev->pnp.bus_id, ACPI_STA_DEFAULT);
> + return;
> + }
> + }
> +#endif
> + *status = sta;
> +}
> +
> void acpi_bus_private_data_handler(acpi_handle handle,
> void *context)
> {
Thanks,
Rafael
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