[Intel-gfx] [PATCH v6 1/3] ACPI / bus: Introduce a list of ids for "always present" devices

[Rafael J. Wysocki]

On Tue, Apr 18, 2017 at 1:54 PM, Hans de Goede <hdegoede at redhat.com> 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 at redhat.com>
> ---
> 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