system76_ec.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <arch/io.h>
#include <console/system76_ec.h>
#include <timer.h>
 
// This is the command region for System76 EC firmware. It must be
// enabled for LPC in the mainboard.
#define SYSTEM76_EC_BASE 0x0E00
#define SYSTEM76_EC_SIZE 256
 
#define REG_CMD 0
#define REG_RESULT 1
 
// When command register is 0, command is complete
#define CMD_FINISHED 0
 
// Print command. Registers are unique for each command
#define CMD_PRINT 4
#define CMD_PRINT_REG_FLAGS 2
#define CMD_PRINT_REG_LEN 3
#define CMD_PRINT_REG_DATA 4
 
static inline uint8_t system76_ec_read(uint8_t addr)
{
        return inb(SYSTEM76_EC_BASE + (uint16_t)addr);
}
 
static inline void system76_ec_write(uint8_t addr, uint8_t data)
{
        outb(data, SYSTEM76_EC_BASE + (uint16_t)addr);
}
 
void system76_ec_init(void)
{
        // Clear entire command region
        for (int i = 0; i < SYSTEM76_EC_SIZE; i++)
                system76_ec_write((uint8_t)i, 0);
}
 
void system76_ec_flush(void)
{
        system76_ec_write(REG_CMD, CMD_PRINT);
 
        // Wait for command completion, for up to 10 milliseconds, with a
        // test period of 1 microsecond
        wait_us(10000, system76_ec_read(REG_CMD) == CMD_FINISHED);
 
        system76_ec_write(CMD_PRINT_REG_LEN, 0);
}
 
void system76_ec_print(uint8_t byte)
{
        uint8_t len = system76_ec_read(CMD_PRINT_REG_LEN);
        system76_ec_write(CMD_PRINT_REG_DATA + len, byte);
        system76_ec_write(CMD_PRINT_REG_LEN, len + 1);
 
        // If we hit the end of the buffer, or were given a newline, flush
        if (byte == '\n' || len >= (SYSTEM76_EC_SIZE - CMD_PRINT_REG_DATA))
                system76_ec_flush();
}