uart_init.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <arch/io.h>
#include <arch/mmio.h>
#include <assert.h>
#include <console/uart.h>
#include <device/pci_def.h>
#include <device/pci_ops.h>
#include <southbridge/intel/lynxpoint/iobp.h>
#include <southbridge/intel/lynxpoint/lp_gpio.h>
#include <southbridge/intel/lynxpoint/pch.h>
#include <types.h>
 
static pci_devfn_t get_uart_pci_device(void)
{
        switch (CONFIG_UART_FOR_CONSOLE) {
                case 0:  return PCI_DEV(0, 0x15, 5);
                case 1:  return PCI_DEV(0, 0x15, 6);
                default: return dead_code_t(pci_devfn_t);
        }
}
 
/* TODO: Figure out if all steps are actually necessary */
void uart_bootblock_init(void)
{
        const pci_devfn_t dev = get_uart_pci_device();
 
        /* Program IOBP GPIODF */
        pch_iobp_update(SIO_IOBP_GPIODF, ~0x131f, 0x131f);
 
        /* Program IOBP CB000180h[5:0] = 111111b (undefined register) */
        pch_iobp_update(0xcb000180, ~0x0000003f, 0x0000003f);
 
        /* Set and enable MMIO BAR */
        pci_write_config32(dev, PCI_BASE_ADDRESS_0, CONFIG_CONSOLE_UART_BASE_ADDRESS);
        pci_or_config16(dev, PCI_COMMAND, PCI_COMMAND_MEMORY);
 
        void *const bar = (void *)(uintptr_t)CONFIG_CONSOLE_UART_BASE_ADDRESS;
 
        /* Initialize LTR */
        clrbits32(bar + SIO_REG_PPR_GEN, SIO_REG_PPR_GEN_LTR_MODE_MASK);
        clrbits32(bar + SIO_REG_PPR_RST, SIO_REG_PPR_RST_ASSERT);
 
        /* Take UART out of reset */
        setbits32(bar + SIO_REG_PPR_RST, SIO_REG_PPR_RST_ASSERT);
 
        /* Set M and N divisor inputs and enable clock */
        uint32_t ppr_clock = 0;
        ppr_clock |= SIO_REG_PPR_CLOCK_EN;
        ppr_clock |= SIO_REG_PPR_CLOCK_UPDATE;
        ppr_clock |= SIO_REG_PPR_CLOCK_N_DIV << 16;
        ppr_clock |= SIO_REG_PPR_CLOCK_M_DIV << 1;
        write32(bar + SIO_REG_PPR_CLOCK, ppr_clock);
}