// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * arch/powerpc/platforms/embedded6xx/usbgecko_udbg.c
 *
 * udbg serial input/output routines for the USB Gecko adapter.
 * Copyright (C) 2008-2009 The GameCube Linux Team
 * Copyright (C) 2008,2009 Albert Herranz
 */

#include <linux/of_address.h>

#include <mm/mmu_decl.h>

#include <asm/io.h>
#include <asm/udbg.h>
#include <asm/fixmap.h>

#include "usbgecko_udbg.h"


#define EXI_CLK_32MHZ           5

#define EXI_CSR                 0x00
#define   EXI_CSR_CLKMASK       (0x7<<4)
#define     EXI_CSR_CLK_32MHZ   (EXI_CLK_32MHZ<<4)
#define   EXI_CSR_CSMASK        (0x7<<7)
#define     EXI_CSR_CS_0        (0x1<<7)  /* Chip Select 001 */

#define EXI_CR                  0x0c
#define   EXI_CR_TSTART         (1<<0)
#define   EXI_CR_WRITE          (1<<2)
#define   EXI_CR_READ_WRITE     (2<<2)
#define   EXI_CR_TLEN(len)      (((len)-1)<<4)

#define EXI_DATA                0x10

#define UG_READ_ATTEMPTS        100
#define UG_WRITE_ATTEMPTS       100


static void __iomem *ug_io_base;

/*
 * Performs one input/output transaction between the exi host and the usbgecko.
 */
static u32 ug_io_transaction(u32 in)
{
        u32 __iomem *csr_reg = ug_io_base + EXI_CSR;
        u32 __iomem *data_reg = ug_io_base + EXI_DATA;
        u32 __iomem *cr_reg = ug_io_base + EXI_CR;
        u32 csr, data, cr;

        /* select */
        csr = EXI_CSR_CLK_32MHZ | EXI_CSR_CS_0;
        out_be32(csr_reg, csr);

        /* read/write */
        data = in;
        out_be32(data_reg, data);
        cr = EXI_CR_TLEN(2) | EXI_CR_READ_WRITE | EXI_CR_TSTART;
        out_be32(cr_reg, cr);

        while (in_be32(cr_reg) & EXI_CR_TSTART)
                barrier();

        /* deselect */
        out_be32(csr_reg, 0);

        /* result */
        data = in_be32(data_reg);

        return data;
}

/*
 * Returns true if an usbgecko adapter is found.
 */
static int ug_is_adapter_present(void)
{
        if (!ug_io_base)
                return 0;

        return ug_io_transaction(0x90000000) == 0x04700000;
}

/*
 * Returns true if the TX fifo is ready for transmission.
 */
static int ug_is_txfifo_ready(void)
{
        return ug_io_transaction(0xc0000000) & 0x04000000;
}

/*
 * Tries to transmit a character.
 * If the TX fifo is not ready the result is undefined.
 */
static void ug_raw_putc(char ch)
{
        ug_io_transaction(0xb0000000 | (ch << 20));
}

/*
 * Transmits a character.
 * It silently fails if the TX fifo is not ready after a number of retries.
 */
static void ug_putc(char ch)
{
        int count = UG_WRITE_ATTEMPTS;

        if (!ug_io_base)
                return;

        if (ch == '\n')
                ug_putc('\r');

        while (!ug_is_txfifo_ready() && count--)
                barrier();
        if (count >= 0)
                ug_raw_putc(ch);
}

/*
 * Returns true if the RX fifo is ready for transmission.
 */
static int ug_is_rxfifo_ready(void)
{
        return ug_io_transaction(0xd0000000) & 0x04000000;
}

/*
 * Tries to receive a character.
 * If a character is unavailable the function returns -1.
 */
static int ug_raw_getc(void)
{
        u32 data = ug_io_transaction(0xa0000000);
        if (data & 0x08000000)
                return (data >> 16) & 0xff;
        else
                return -1;
}

/*
 * Receives a character.
 * It fails if the RX fifo is not ready after a number of retries.
 */
static int ug_getc(void)
{
        int count = UG_READ_ATTEMPTS;

        if (!ug_io_base)
                return -1;

        while (!ug_is_rxfifo_ready() && count--)
                barrier();
        return ug_raw_getc();
}

/*
 * udbg functions.
 *
 */

/*
 * Transmits a character.
 */
static void ug_udbg_putc(char ch)
{
        ug_putc(ch);
}

/*
 * Receives a character. Waits until a character is available.
 */
static int ug_udbg_getc(void)
{
        int ch;

        while ((ch = ug_getc()) == -1)
                barrier();
        return ch;
}

/*
 * Receives a character. If a character is not available, returns -1.
 */
static int ug_udbg_getc_poll(void)
{
        if (!ug_is_rxfifo_ready())
                return -1;
        return ug_getc();
}

/*
 * Checks if a USB Gecko adapter is inserted in any memory card slot.
 */
static void __iomem *__init ug_udbg_probe(void __iomem *exi_io_base)
{
        int i;

        /* look for a usbgecko on memcard slots A and B */
        for (i = 0; i < 2; i++) {
                ug_io_base = exi_io_base + 0x14 * i;
                if (ug_is_adapter_present())
                        break;
        }
        if (i == 2)
                ug_io_base = NULL;
        return ug_io_base;

}

/*
 * USB Gecko udbg support initialization.
 */
void __init ug_udbg_init(void)
{
        struct device_node *np;
        void __iomem *exi_io_base;

        if (ug_io_base)
                udbg_printf("%s: early -> final\n", __func__);

        np = of_find_compatible_node(NULL, NULL, "nintendo,flipper-exi");
        if (!np) {
                udbg_printf("%s: EXI node not found\n", __func__);
                goto out;
        }

        exi_io_base = of_iomap(np, 0);
        if (!exi_io_base) {
                udbg_printf("%s: failed to setup EXI io base\n", __func__);
                goto done;
        }

        if (!ug_udbg_probe(exi_io_base)) {
                udbg_printf("usbgecko_udbg: not found\n");
                iounmap(exi_io_base);
        } else {
                udbg_putc = ug_udbg_putc;
                udbg_getc = ug_udbg_getc;
                udbg_getc_poll = ug_udbg_getc_poll;
                udbg_printf("usbgecko_udbg: ready\n");
        }

done:
        of_node_put(np);
out:
        return;
}

#ifdef CONFIG_PPC_EARLY_DEBUG_USBGECKO

static phys_addr_t __init ug_early_grab_io_addr(void)
{
#if defined(CONFIG_GAMECUBE)
        return 0x0c000000;
#elif defined(CONFIG_WII)
        return 0x0d000000;
#else
#error Invalid platform for USB Gecko based early debugging.
#endif
}

/*
 * USB Gecko early debug support initialization for udbg.
 */
void __init udbg_init_usbgecko(void)
{
        void __iomem *early_debug_area;
        void __iomem *exi_io_base;

        /*
         * At this point we have a BAT already setup that enables I/O
         * to the EXI hardware.
         *
         * The BAT uses a virtual address range reserved at the fixmap.
         * This must match the virtual address configured in
         * head_32.S:setup_usbgecko_bat().
         */
        early_debug_area = (void __iomem *)__fix_to_virt(FIX_EARLY_DEBUG_BASE);
        exi_io_base = early_debug_area + 0x00006800;

        /* try to detect a USB Gecko */
        if (!ug_udbg_probe(exi_io_base))
                return;

        /* we found a USB Gecko, load udbg hooks */
        udbg_putc = ug_udbg_putc;
        udbg_getc = ug_udbg_getc;
        udbg_getc_poll = ug_udbg_getc_poll;

        /*
         * Prepare again the same BAT for MMU_init.
         * This allows udbg I/O to continue working after the MMU is
         * turned on for real.
         * It is safe to continue using the same virtual address as it is
         * a reserved fixmap area.
         */
        setbat(1, (unsigned long)early_debug_area,
               ug_early_grab_io_addr(), 128*1024, PAGE_KERNEL_NCG);
}

#endif /* CONFIG_PPC_EARLY_DEBUG_USBGECKO */