early_printk.c

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/*
 *  Atheros AR7XXX/AR9XXX SoC early printk support
 *
 *  Copyright (C) 2008-2011 Gabor Juhos <[email protected]>
 *  Copyright (C) 2008 Imre Kaloz <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 */

#include <linux/io.h>
#include <linux/errno.h>
#include <linux/serial_reg.h>
#include <asm/addrspace.h>

#include <asm/mach-ath79/ath79.h>
#include <asm/mach-ath79/ar71xx_regs.h>
#include <asm/mach-ath79/ar933x_uart.h>

static void (*_prom_putchar) (unsigned char);

static inline void prom_putchar_wait(void __iomem *reg, u32 mask, u32 val)
{
    u32 t;

    do {
        t = __raw_readl(reg);
        if ((t & mask) == val)
            break;
    } while (1);
}

static void prom_putchar_ar71xx(unsigned char ch)
{
    void __iomem *base = (void __iomem *)(KSEG1ADDR(AR71XX_UART_BASE));

    prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
    __raw_writel(ch, base + UART_TX * 4);
    prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
}

static void prom_putchar_ar933x(unsigned char ch)
{
    void __iomem *base = (void __iomem *)(KSEG1ADDR(AR933X_UART_BASE));

    prom_putchar_wait(base + AR933X_UART_DATA_REG, AR933X_UART_DATA_TX_CSR,
              AR933X_UART_DATA_TX_CSR);
    __raw_writel(AR933X_UART_DATA_TX_CSR | ch, base + AR933X_UART_DATA_REG);
    prom_putchar_wait(base + AR933X_UART_DATA_REG, AR933X_UART_DATA_TX_CSR,
              AR933X_UART_DATA_TX_CSR);
}

static void prom_putchar_dummy(unsigned char ch)
{
    /* nothing to do */
}

static void prom_putchar_init(void)
{
    void __iomem *base;
    u32 id;

    base = (void __iomem *)(KSEG1ADDR(AR71XX_RESET_BASE));
    id = __raw_readl(base + AR71XX_RESET_REG_REV_ID);
    id &= REV_ID_MAJOR_MASK;

    switch (id) {
    case REV_ID_MAJOR_AR71XX:
    case REV_ID_MAJOR_AR7240:
    case REV_ID_MAJOR_AR7241:
    case REV_ID_MAJOR_AR7242:
    case REV_ID_MAJOR_AR913X:
    case REV_ID_MAJOR_AR9341:
    case REV_ID_MAJOR_AR9342:
    case REV_ID_MAJOR_AR9344:
        _prom_putchar = prom_putchar_ar71xx;
        break;

    case REV_ID_MAJOR_AR9330:
    case REV_ID_MAJOR_AR9331:
        _prom_putchar = prom_putchar_ar933x;
        break;

    default:
        _prom_putchar = prom_putchar_dummy;
        break;
    }
}

void prom_putchar(unsigned char ch)
{
    if (!_prom_putchar)
        prom_putchar_init();

    _prom_putchar(ch);
}