sw/device/lib/testing/test_rom/puppeteer_utils/uart.cc

// Copyright 2022 Google LLC
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

#include "sw/device/lib/testing/test_rom/puppeteer_utils/uart.h"

#include "hw/top_matcha/sw/autogen/top_matcha.h"  // Generated.
#include "pinmux_regs.h"  // NOLINT(build/include_subdir) Generated.
#include "sw/device/lib/testing/test_rom/puppeteer_utils/opentitan_uart.h"
#include "uart_regs.h"  // NOLINT(build/include_subdir) Generated.

// Opentitan toolchain doesn't invoke -lgcc, so the clk divider needs to be
// computed in preprocessor instead of in runtime to bypass the uint64 division.
#ifndef TINY_IO_PERIPHERAL_CLOCK
#define TINY_IO_PERIPHERAL_CLOCK 2500000ull
#endif
#ifndef TINY_IO_BUAD_RATE
#define TINY_IO_BUAD_RATE 115200ull
#endif

// The UART's clock scaler is a 16-bit accumulator that needs to overflow 16
// times per bit period to account for oversampling. We do this bit of math
// using 64-bit ints so we don't overflow, even though the resulting divider
// setting is only 16 bits.
#define TINY_IO_CLK_DIV \
  (16ull * 65536ull * TINY_IO_BUAD_RATE) / TINY_IO_PERIPHERAL_CLOCK

// Simple helper method to initialize a TinyIO interface to point to Ibex's
// UART0 peripheral.
TinyIO init_uart0() {
  // To use UART0, we need to set up the pinmux to connect uart 0 to some MIO
  // pads and set the pin drive modes.

  volatile uint32_t* insel_base = reinterpret_cast<uint32_t*>(
      TOP_MATCHA_PINMUX_AON_BASE_ADDR + PINMUX_MIO_PERIPH_INSEL_0_REG_OFFSET);
  volatile uint32_t* outsel_base = reinterpret_cast<uint32_t*>(
      TOP_MATCHA_PINMUX_AON_BASE_ADDR + PINMUX_MIO_OUTSEL_0_REG_OFFSET);

  // Uart0Rx input is tied to MIO pad 25 (GPIO C3).
  insel_base[kTopMatchaPinmuxPeripheralInUart0Rx] = kTopMatchaPinmuxInselIoc3;

  // MIO pad 25 output (GPIO C3) is set to High-Z.
  outsel_base[kTopMatchaPinmuxMioOutIoc3] = kTopMatchaPinmuxOutselConstantHighZ;

  // MIO pad 26 output (GPIO C4) is set to Uart0Tx.
  outsel_base[kTopMatchaPinmuxMioOutIoc4] = kTopMatchaPinmuxOutselUart0Tx;

  // Turn on the UART peripheral.
  uint64_t clk_div = TINY_IO_CLK_DIV;

  volatile OpenTitanUart* uart =
      reinterpret_cast<OpenTitanUart*>(TOP_MATCHA_UART0_BASE_ADDR);
  uart->CTRL = 0;
  uart->FIFO_CTRL =
      (1 << UART_FIFO_CTRL_RXRST_BIT) | (1 << UART_FIFO_CTRL_TXRST_BIT);
  uart->OVRD = 0;
  uart->VAL = 0;
  uart->INTR_ENABLE = 0;
  uart->INTR_STATE = ~0;
  uart->CTRL =
      (clk_div << 16) | (1 << UART_CTRL_TX_BIT) | (1 << UART_CTRL_RX_BIT);

  // The "get byte" and "put byte" methods for the bootrom just busy-wait while
  // the queue is empty/full.

  auto getter = [](void* user) -> uint8_t {
    volatile OpenTitanUart* uart = reinterpret_cast<OpenTitanUart*>(user);
    while (uart->STATUS & (1 << UART_STATUS_RXEMPTY_BIT)) {
    }
    return uart->RDATA;
  };

  auto setter = [](void* user, uint8_t b) {
    volatile OpenTitanUart* uart = reinterpret_cast<OpenTitanUart*>(user);
    while (uart->STATUS & (1 << UART_STATUS_TXFULL_BIT)) {
    }
    uart->WDATA = b;
  };

  return {getter, setter, reinterpret_cast<void*>(TOP_MATCHA_UART0_BASE_ADDR)};
}

void init_smc_uart() {
  volatile uint32_t* insel_base = reinterpret_cast<uint32_t*>(
      TOP_MATCHA_PINMUX_AON_BASE_ADDR + PINMUX_MIO_PERIPH_INSEL_0_REG_OFFSET);
  volatile uint32_t* outsel_base = reinterpret_cast<uint32_t*>(
      TOP_MATCHA_PINMUX_AON_BASE_ADDR + PINMUX_MIO_OUTSEL_0_REG_OFFSET);

  // SmcUartRx input is tied to MIO pad 32 (GPIO C10).
  insel_base[kTopMatchaPinmuxPeripheralInSmcUartRx] =
      kTopMatchaPinmuxInselIoc10;
  // MIO pad 32 output (GPIO C10) is set to High-Z.
  outsel_base[kTopMatchaPinmuxMioOutIoc10] =
      kTopMatchaPinmuxOutselConstantHighZ;
  // MIO pad 33 output (GPIO C11) is set to SmcTx.
  outsel_base[kTopMatchaPinmuxMioOutIoc11] = kTopMatchaPinmuxOutselSmcUartTx;
}