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// Copyright lowRISC contributors (OpenTitan project).
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

use anyhow::{bail, Result};
use std::cell::RefCell;
use std::rc::Rc;

use crate::io::gpio;
use crate::io::spi::{AssertChipSelect, MaxSizes, SpiError, Target, Transfer, TransferMode};
use crate::transport::chip_whisperer::usb::Backend;
use crate::transport::TransportError;

use super::board::Board;

pub struct Spi<B: Board> {
    device: Rc<RefCell<Backend<B>>>,
}

impl<B: Board> Spi<B> {
    pub fn open(device: Rc<RefCell<Backend<B>>>) -> Result<Self> {
        {
            let usb = device.borrow();
            usb.spi1_enable(true)?;
        }

        Ok(Spi { device })
    }

    // Perform a SPI transaction.
    fn spi_transaction(&self, transaction: &mut [Transfer]) -> Result<()> {
        let usb = self.device.borrow();
        for transfer in transaction.iter_mut() {
            match transfer {
                Transfer::Read(buf) => usb.spi1_read(buf)?,
                Transfer::Write(buf) => usb.spi1_write(buf)?,
                Transfer::Both(wbuf, rbuf) => usb.spi1_both(wbuf, rbuf)?,
                _ => bail!(TransportError::UnsupportedOperation),
            }
        }
        Ok(())
    }
}

impl<B: Board> Target for Spi<B> {
    fn get_transfer_mode(&self) -> Result<TransferMode> {
        Ok(TransferMode::Mode0)
    }
    fn set_transfer_mode(&self, mode: TransferMode) -> Result<()> {
        log::warn!(
            "set_transfer_mode to {:?}, but only Mode0 is supported on this device",
            mode
        );
        Ok(())
    }

    fn get_bits_per_word(&self) -> Result<u32> {
        Ok(8)
    }
    fn set_bits_per_word(&self, bits_per_word: u32) -> Result<()> {
        match bits_per_word {
            8 => Ok(()),
            _ => Err(SpiError::InvalidWordSize(bits_per_word).into()),
        }
    }

    fn get_max_speed(&self) -> Result<u32> {
        // FIXME: what is the speed of the SAM3U SPI interface on the Chip Whisperer board?
        Ok(6_000_000)
    }
    fn set_max_speed(&self, frequency: u32) -> Result<()> {
        log::warn!(
            "set_max_speed to {:?}, but this device doesn't support changing speeds.",
            frequency
        );
        Ok(())
    }

    fn supports_bidirectional_transfer(&self) -> Result<bool> {
        Ok(true)
    }

    fn supports_tpm_poll(&self) -> Result<bool> {
        Ok(false)
    }

    fn set_pins(
        &self,
        serial_clock: Option<&Rc<dyn gpio::GpioPin>>,
        host_out_device_in: Option<&Rc<dyn gpio::GpioPin>>,
        host_in_device_out: Option<&Rc<dyn gpio::GpioPin>>,
        chip_select: Option<&Rc<dyn gpio::GpioPin>>,
        gsc_ready: Option<&Rc<dyn gpio::GpioPin>>,
    ) -> Result<()> {
        match (
            serial_clock,
            host_out_device_in,
            host_in_device_out,
            chip_select,
            gsc_ready,
        ) {
            (Some(clk), Some(sdo), Some(sdi), Some(cs), None) => {
                let usb = self.device.borrow();
                usb.spi1_enable(false)?;
                usb.spi1_setpins(
                    sdo.get_internal_pin_name().unwrap(),
                    sdi.get_internal_pin_name().unwrap(),
                    clk.get_internal_pin_name().unwrap(),
                    cs.get_internal_pin_name().unwrap(),
                )?;
                usb.spi1_enable(true)?;
                Ok(())
            }
            (None, None, None, None, None) => Ok(()),
            _ => {
                // Explicitly choosing pins for some of the SPI signals, while leaving others at
                // their default, is not supported.
                Err(TransportError::UnsupportedOperation.into())
            }
        }
    }

    fn get_max_transfer_count(&self) -> Result<usize> {
        // Arbitrary value: number of `Transfers` that can be in a single transaction.
        Ok(42)
    }

    fn get_max_transfer_sizes(&self) -> Result<MaxSizes> {
        Ok(MaxSizes {
            read: 65536,
            write: 65536,
        })
    }

    fn run_transaction(&self, transaction: &mut [Transfer]) -> Result<()> {
        // Assert CS# (drive low).
        self.device.borrow().spi1_set_cs_pin(false)?;
        // Translate SPI Read/Write Transactions into Chip Whisperer spi operations.
        let result = self.spi_transaction(transaction);
        // Release CS# (allow to float high).
        self.device.borrow().spi1_set_cs_pin(true)?;
        result
    }

    fn assert_cs(self: Rc<Self>) -> Result<AssertChipSelect> {
        Err(TransportError::UnsupportedOperation.into())
    }
}