// SPDX-License-Identifier: GPL-2.0

mod boot;

use kernel::{
    device,
    dma::{
        CoherentAllocation,
        DmaAddress, //
    },
    dma_write,
    pci,
    prelude::*,
    transmute::AsBytes, //
};

pub(crate) mod cmdq;
pub(crate) mod commands;
mod fw;
mod sequencer;

pub(crate) use fw::{
    GspFwWprMeta,
    LibosParams, //
};

use crate::{
    gsp::cmdq::Cmdq,
    gsp::fw::{
        GspArgumentsPadded,
        LibosMemoryRegionInitArgument, //
    },
    num,
};

pub(crate) const GSP_PAGE_SHIFT: usize = 12;
pub(crate) const GSP_PAGE_SIZE: usize = 1 << GSP_PAGE_SHIFT;

/// Number of GSP pages to use in a RM log buffer.
const RM_LOG_BUFFER_NUM_PAGES: usize = 0x10;

/// Array of page table entries, as understood by the GSP bootloader.
#[repr(C)]
struct PteArray<const NUM_ENTRIES: usize>([u64; NUM_ENTRIES]);

/// SAFETY: arrays of `u64` implement `AsBytes` and we are but a wrapper around one.
unsafe impl<const NUM_ENTRIES: usize> AsBytes for PteArray<NUM_ENTRIES> {}

impl<const NUM_PAGES: usize> PteArray<NUM_PAGES> {
    /// Returns the page table entry for `index`, for a mapping starting at `start`.
    // TODO: Replace with `IoView` projection once available.
    fn entry(start: DmaAddress, index: usize) -> Result<u64> {
        start
            .checked_add(num::usize_as_u64(index) << GSP_PAGE_SHIFT)
            .ok_or(EOVERFLOW)
    }
}

/// The logging buffers are byte queues that contain encoded printf-like
/// messages from GSP-RM.  They need to be decoded by a special application
/// that can parse the buffers.
///
/// The 'loginit' buffer contains logs from early GSP-RM init and
/// exception dumps.  The 'logrm' buffer contains the subsequent logs. Both are
/// written to directly by GSP-RM and can be any multiple of GSP_PAGE_SIZE.
///
/// The physical address map for the log buffer is stored in the buffer
/// itself, starting with offset 1. Offset 0 contains the "put" pointer (pp).
/// Initially, pp is equal to 0. If the buffer has valid logging data in it,
/// then pp points to index into the buffer where the next logging entry will
/// be written. Therefore, the logging data is valid if:
///   1 <= pp < sizeof(buffer)/sizeof(u64)
struct LogBuffer(CoherentAllocation<u8>);

impl LogBuffer {
    /// Creates a new `LogBuffer` mapped on `dev`.
    fn new(dev: &device::Device<device::Bound>) -> Result<Self> {
        const NUM_PAGES: usize = RM_LOG_BUFFER_NUM_PAGES;

        let mut obj = Self(CoherentAllocation::<u8>::alloc_coherent(
            dev,
            NUM_PAGES * GSP_PAGE_SIZE,
            GFP_KERNEL | __GFP_ZERO,
        )?);

        let start_addr = obj.0.dma_handle();

        // SAFETY: `obj` has just been created and we are its sole user.
        let pte_region = unsafe {
            obj.0
                .as_slice_mut(size_of::<u64>(), NUM_PAGES * size_of::<u64>())?
        };

        // Write values one by one to avoid an on-stack instance of `PteArray`.
        for (i, chunk) in pte_region.chunks_exact_mut(size_of::<u64>()).enumerate() {
            let pte_value = PteArray::<0>::entry(start_addr, i)?;

            chunk.copy_from_slice(&pte_value.to_ne_bytes());
        }

        Ok(obj)
    }
}

/// GSP runtime data.
#[pin_data]
pub(crate) struct Gsp {
    /// Libos arguments.
    pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
    /// Init log buffer.
    loginit: LogBuffer,
    /// Interrupts log buffer.
    logintr: LogBuffer,
    /// RM log buffer.
    logrm: LogBuffer,
    /// Command queue.
    pub(crate) cmdq: Cmdq,
    /// RM arguments.
    rmargs: CoherentAllocation<GspArgumentsPadded>,
}

impl Gsp {
    // Creates an in-place initializer for a `Gsp` manager for `pdev`.
    pub(crate) fn new(pdev: &pci::Device<device::Bound>) -> impl PinInit<Self, Error> + '_ {
        pin_init::pin_init_scope(move || {
            let dev = pdev.as_ref();

            Ok(try_pin_init!(Self {
                libos: CoherentAllocation::<LibosMemoryRegionInitArgument>::alloc_coherent(
                    dev,
                    GSP_PAGE_SIZE / size_of::<LibosMemoryRegionInitArgument>(),
                    GFP_KERNEL | __GFP_ZERO,
                )?,
                loginit: LogBuffer::new(dev)?,
                logintr: LogBuffer::new(dev)?,
                logrm: LogBuffer::new(dev)?,
                cmdq: Cmdq::new(dev)?,
                rmargs: CoherentAllocation::<GspArgumentsPadded>::alloc_coherent(
                    dev,
                    1,
                    GFP_KERNEL | __GFP_ZERO,
                )?,
                _: {
                    // Initialise the logging structures. The OpenRM equivalents are in:
                    // _kgspInitLibosLoggingStructures (allocates memory for buffers)
                    // kgspSetupLibosInitArgs_IMPL (creates pLibosInitArgs[] array)
                    dma_write!(
                        libos, [0]?, LibosMemoryRegionInitArgument::new("LOGINIT", &loginit.0)
                    );
                    dma_write!(
                        libos, [1]?, LibosMemoryRegionInitArgument::new("LOGINTR", &logintr.0)
                    );
                    dma_write!(libos, [2]?, LibosMemoryRegionInitArgument::new("LOGRM", &logrm.0));
                    dma_write!(rmargs, [0]?.inner, fw::GspArgumentsCached::new(cmdq));
                    dma_write!(libos, [3]?, LibosMemoryRegionInitArgument::new("RMARGS", rmargs));
                },
            }))
        })
    }
}