syd 3.52.0

rock-solid application kernel
Documentation 
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// SPDX-License-Identifier: GPL-2.0

//! GPU Firmware (`GFW`) support, a.k.a `devinit`.
//!
//! Upon reset, the GPU runs some firmware code from the BIOS to setup its core parameters. Most of
//! the GPU is considered unusable until this step is completed, so we must wait on it before
//! performing driver initialization.
//!
//! A clarification about devinit terminology: devinit is a sequence of register read/writes after
//! reset that performs tasks such as:
//! 1. Programming VRAM memory controller timings.
//! 2. Power sequencing.
//! 3. Clock and PLL configuration.
//! 4. Thermal management.
//!
//! devinit itself is a 'script' which is interpreted by an interpreter program typically running
//! on the PMU microcontroller.
//!
//! Note that the devinit sequence also needs to run during suspend/resume.

use kernel::{
    io::{
        poll::read_poll_timeout,
        Io, //
    },
    prelude::*,
    time::Delta, //
};

use crate::{
    driver::Bar0,
    regs, //
};

/// Wait for the `GFW` (GPU firmware) boot completion signal (`GFW_BOOT`), or a 4 seconds timeout.
///
/// Upon GPU reset, several microcontrollers (such as PMU, SEC2, GSP etc) run some firmware code to
/// setup its core parameters. Most of the GPU is considered unusable until this step is completed,
/// so it must be waited on very early during driver initialization.
///
/// The `GFW` code includes several components that need to execute before the driver loads. These
/// components are located in the VBIOS ROM and executed in a sequence on these different
/// microcontrollers. The devinit sequence typically runs on the PMU, and the FWSEC runs on the
/// GSP.
///
/// This function waits for a signal indicating that core initialization is complete. Before this
/// signal is received, little can be done with the GPU. This signal is set by the FWSEC running on
/// the GSP in Heavy-secured mode.
pub(crate) fn wait_gfw_boot_completion(bar: &Bar0) -> Result {
    // Before accessing the completion status in `NV_PGC6_AON_SECURE_SCRATCH_GROUP_05`, we must
    // first check `NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_PRIV_LEVEL_MASK`. This is because
    // `NV_PGC6_AON_SECURE_SCRATCH_GROUP_05` becomes accessible only after the secure firmware
    // (FWSEC) lowers the privilege level to allow CPU (LS/Light-secured) access. We can only
    // safely read the status register from CPU (LS/Light-secured) once the mask indicates
    // that the privilege level has been lowered.
    //
    // TIMEOUT: arbitrarily large value. GFW starts running immediately after the GPU is put out of
    // reset, and should complete in less time than that.
    read_poll_timeout(
        || {
            Ok(
                // Check that FWSEC has lowered its protection level before reading the GFW_BOOT
                // status.
                bar.read(regs::NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_PRIV_LEVEL_MASK)
                    .read_protection_level0()
                    && bar
                        .read(regs::NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_0_GFW_BOOT)
                        .completed(),
            )
        },
        |&gfw_booted| gfw_booted,
        Delta::from_millis(1),
        Delta::from_secs(4),
    )
    .map(|_| ())
}