mc146818rtc_boot.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <stdint.h>
#include <console/console.h>
#include <pc80/mc146818rtc.h>
#include <fallback.h>
 
#if  CONFIG_MAX_REBOOT_CNT > 15
#error "CONFIG_MAX_REBOOT_CNT too high"
#endif
 
static int boot_count(uint8_t rtc_byte)
{
        return rtc_byte >> 4;
}
 
static uint8_t increment_boot_count(uint8_t rtc_byte)
{
        return rtc_byte + (1 << 4);
}
 
static uint8_t boot_set_fallback(uint8_t rtc_byte)
{
        return rtc_byte & ~RTC_BOOT_NORMAL;
}
 
static int boot_use_normal(uint8_t rtc_byte)
{
        return rtc_byte & RTC_BOOT_NORMAL;
}
 
int do_normal_boot(void)
{
        unsigned char byte;
 
        if (cmos_error() || (CONFIG(USE_OPTION_TABLE) && !cmos_lb_cks_valid())) {
                printk(BIOS_WARNING,
                       "Invalid CMOS checksum detected! Force fallback boot...\n");
                byte = cmos_read(RTC_BOOT_BYTE);
                byte &= boot_set_fallback(byte) & 0x0f;
                byte |= 0xf << 4;
                cmos_write(byte, RTC_BOOT_BYTE);
        }
 
        /* The RTC_BOOT_BYTE is now o.k. see where to go. */
        byte = cmos_read(RTC_BOOT_BYTE);
 
        /* Are we attempting to boot normally? */
        if (boot_use_normal(byte)) {
                /* Are we already at the max count? */
                if (boot_count(byte) < CONFIG_MAX_REBOOT_CNT)
                        byte = increment_boot_count(byte);
                else
                        byte = boot_set_fallback(byte);
        }
 
        /* Save the boot byte */
        cmos_write(byte, RTC_BOOT_BYTE);
 
        /* Return selected code path for this boot attempt */
        return boot_use_normal(byte);
}