// SPDX-License-Identifier: GPL-2.0-only
/*
 * Intel CE4100  platform specific setup code
 *
 * (C) Copyright 2010 Intel Corporation
 */

#include <linux/init.h>
#include <linux/io.h>
#include <linux/types.h>

#include <asm/ce4100.h>
#include <asm/fixmap.h>
#include <asm/page.h>

#include <linux/serial_reg.h>
#include <linux/serial_8250.h>

static unsigned int mem_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return readl(p->membase + offset);
}

/*
 * The UART Tx interrupts are not set under some conditions and therefore serial
 * transmission hangs. This is a silicon issue and has not been root caused. The
 * workaround for this silicon issue checks UART_LSR_THRE bit and UART_LSR_TEMT
 * bit of LSR register in interrupt handler to see whether at least one of these
 * two bits is set, if so then process the transmit request. If this workaround
 * is not applied, then the serial transmission may hang. This workaround is for
 * errata number 9 in Errata - B step.
*/
static u32 ce4100_mem_serial_in(struct uart_port *p, unsigned int offset)
{
        u32 ret, ier, lsr;

        ret = mem_serial_in(p, offset);
        if (offset != UART_IIR || !(ret & UART_IIR_NO_INT))
                return ret;

        /* see if the TX interrupt should have really set */
        ier = mem_serial_in(p, UART_IER);
        /* see if the UART's XMIT interrupt is enabled */
        if (!(ier & UART_IER_THRI))
                return ret;

        lsr = mem_serial_in(p, UART_LSR);
        /* now check to see if the UART should be generating an interrupt (but isn't) */
        if (lsr & (UART_LSR_THRE | UART_LSR_TEMT))
                ret &= ~UART_IIR_NO_INT;

        return ret;
}

static void ce4100_mem_serial_out(struct uart_port *p, unsigned int offset, u32 value)
{
        offset <<= p->regshift;
        writel(value, p->membase + offset);
}

static void ce4100_serial_fixup(int port, struct uart_port *up, u32 *capabilities)
{
#ifdef CONFIG_EARLY_PRINTK
        /*
         * Override the legacy port configuration that comes from
         * asm/serial.h. Using the ioport driver then switching to the
         * PCI memmaped driver hangs the IOAPIC.
         */
        if (up->iotype != UPIO_MEM32) {
                up->uartclk = 14745600;
                up->mapbase = 0xdffe0200;
                set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, up->mapbase & PAGE_MASK);
                up->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
                up->membase += up->mapbase & ~PAGE_MASK;
                up->mapbase += port * 0x100;
                up->membase += port * 0x100;
                up->iotype = UPIO_MEM32;
                up->regshift = 2;
                up->irq = 4;
        }
#endif
        up->iobase = 0;
        up->serial_in = ce4100_mem_serial_in;
        up->serial_out = ce4100_mem_serial_out;

        *capabilities |= (1 << 12);
}

void __init sdv_serial_fixup(void)
{
        serial8250_set_isa_configurator(ce4100_serial_fixup);
}