class PchEngine

`mmio_buffer` must outlive this instance.

If `enabled` is true, the north (main) display engine notifies the PCH

display engine of resets, and waits for it to acknowledge.

This method must be called with `enabled` set to true during the cold-boot

display engine initialization sequence.

Overwrites the PCH clocking registers with cached values.

This method performs MMIO writes unconditionally. It must only be called

during the display engine initialization sequence, when resuming from a

low-power (suspended) state.

Overwrites most PCH configuration registers with cached values.

This method restores all PCH configuration registers, *except* for the

registers covered by RestoreClockParameters(). This separation is needed to

comply with the mode set sequences documented by the Intel PRMs.

This method performs MMIO writes unconditionally. It must only be called

when resuming from a low-power (suspended) state, after the display engine

is re-initialized. In particular, RestoreClockParameters() must have been

already called.

Calling this method will restore the PCH to the configuration it had before

entering a low-power (suspended) state, with the following exceptions:

* The panel will be powered off, awaiting pipe and transcoder

configuration.

* The backlight PWM will be disabled, since the panel is powered off.

Reports the current PCH clocking configuration.

This method is intended for retrieving the configuration applied by the

boot firmware. SetClockParameters() can perform any needed adjustments.

Updates the PCH clocking configuration.

No MMIO writes are performed if `parameters` already matches the clocking

configuration.

Fixes clocking parameters that are obviously incorrect.

Trivially destructible.

Reports the current PCH panel configuration.

This method is intended for retrieving the configuration applied by the

boot firmware. SetPanelParameters() can perform any needed adjustments.

The caller should ensure that the PCH clocking is configured correctly

before calling this method. The result is not meaningful if the PCH

clocking is incorrect.

Updates the PCH panel configuration.

The caller must ensure that the PCH clocks are configured correctly before

calling this method.

This method preserves (modulo precision errors) the PWM backlight's

brightness level when the PWM frequency changes. The brightness level will

be set to 0% if the PWM was not previously configured. The brightness level

will be normalized to 100% if it was (incorrectly) set above 100%.

No MMIO writes are performed if `parameters` already matches the panel

configuration (unless the PWM brightness level must be normalized).

Reports the target configuration of the PCH panel power subsystem.

This method is intended for retrieving the configuration applied by the

boot firmware. SetPanelPowerTarget() can drive the transition to new power

states.

Returns the panel power state reported by the PCH.

This method is not idempotent.

Waits for the PCH panel power sequence to reach a given state.

Returns true if the PCH panel reached the given state within the allotted

time. Returns false if the timeout ran out before the PCH panel reached the

desired state.

While `power_state` can be any value, the meaningful values are kPoweredUp

and kPoweredDown.

`timeout_us` must be positive. The eDP 1.4 standard allows for 90ms. The

SPWG Notebook Panel standard allows for 210ms. The Atlas panel needs almost

400ms.

Updates the PCH panel power subsystem's target configuration.

The caller must ensure that the PCH panel parameters are configured

correctly before calling this method with `power_on` set to true.

The caller must ensure that the PCH brightness PWM is configured correctly

before calling this method with `backlight_on` set to true.

No MMIO writes are performed if `power_target` already matches the panel

power subsystem's target.

The brightness level created by the PCH panel backlight PWM.

Returns a value between 0.0 (no brightness) and 1.0 (maximum brightness).

Sets the brightness level created by the PCH panel backlight PWM.

`brightness` must be between 0.0 (no brightness) and 1.0 (maximum

brightness).

The caller must ensure that the PCH backlight brightness PWM is configured

correctly before calling this method.