spcr.c

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/*
 * Copyright (C) 2025 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <errno.h>
#include <ipxe/serial.h>
#include <ipxe/pci.h>
#include <ipxe/ns16550.h>
#include <ipxe/spcr.h>

/** @file
 *
 * ACPI Serial Port Console Redirection (SPCR)
 *
 */

#ifdef SERIAL_SPCR
#define SERIAL_PREFIX_spcr
#else
#define SERIAL_PREFIX_spcr __spcr_
#endif

/** SPCR-defined UART */
static struct uart spcr_uart = {
        .refcnt = REF_INIT ( ref_no_free ),
        .name = "SPCR",
};

/** SPCR-defined 16550 UART */
static struct ns16550_uart spcr_ns16550 = {
        .clock = NS16550_CLK_DEFAULT,
};

/** Base baud rate for SPCR divisors */
#define SPCR_BAUD_BASE 115200

/** SPCR baud rate divisors */
static const uint8_t spcr_baud_divisor[SPCR_BAUD_MAX] = {
        [SPCR_BAUD_2400] = ( SPCR_BAUD_BASE / 2400 ),
        [SPCR_BAUD_4800] = ( SPCR_BAUD_BASE / 4800 ),
        [SPCR_BAUD_9600] = ( SPCR_BAUD_BASE / 9600 ),
        [SPCR_BAUD_19200] = ( SPCR_BAUD_BASE / 19200 ),
        [SPCR_BAUD_38400] = ( SPCR_BAUD_BASE / 38400 ),
        [SPCR_BAUD_57600] = ( SPCR_BAUD_BASE / 57600 ),
        [SPCR_BAUD_115200] = ( SPCR_BAUD_BASE / 115200 ),
};

/**
 * Configure 16550-based serial console
 *
 * @v spcr              SPCR table
 * @v uart              UART to configure
 * @ret rc              Return status code
 */
static int spcr_16550 ( struct spcr_table *spcr, struct uart *uart ) {
        struct ns16550_uart *ns16550 = &spcr_ns16550;

        /* Set base address */
        ns16550->base = acpi_ioremap ( &spcr->base, NS16550_LEN );
        if ( ! ns16550->base ) {
                DBGC ( uart, "SPCR could not map registers\n" );
                return -ENODEV;
        }

        /* Set clock frequency, if specified */
        if ( spcr->clock )
                ns16550->clock = le32_to_cpu ( spcr->clock );

        /* Configure UART as a 16550 */
        uart->op = &ns16550_operations;
        uart->priv = ns16550;

        return 0;
}

/**
 * Identify default serial console
 *
 * @ret uart            Default serial console UART, or NULL
 */
static struct uart * spcr_console ( void ) {
        struct uart *uart = &spcr_uart;
        struct spcr_table *spcr;
        unsigned int baud;
        int rc;

        /* Locate SPCR table */
        spcr = container_of ( acpi_table ( SPCR_SIGNATURE, 0 ),
                              struct spcr_table, acpi );
        if ( ! spcr ) {
                DBGC ( uart, "SPCR found no table\n" );
                goto err_table;
        }
        DBGC2 ( uart, "SPCR found table:\n" );
        DBGC2_HDA ( uart, 0, spcr, sizeof ( *spcr ) );
        DBGC ( uart, "SPCR is type %d at %02x:%08llx\n",
               spcr->type, spcr->base.type,
               ( ( unsigned long long ) le64_to_cpu ( spcr->base.address ) ) );
        if ( spcr->pci_vendor_id != cpu_to_le16 ( PCI_ANY_ID ) ) {
                DBGC ( uart, "SPCR is PCI " PCI_FMT " (%04x:%04x)\n",
                       spcr->pci_segment, spcr->pci_bus, spcr->pci_dev,
                       spcr->pci_func, le16_to_cpu ( spcr->pci_vendor_id ),
                       le16_to_cpu ( spcr->pci_device_id ) );
        }

        /* Get baud rate */
        baud = 0;
        if ( le32_to_cpu ( spcr->acpi.length ) >=
             ( offsetof ( typeof ( *spcr ), precise ) +
               sizeof ( spcr->precise ) ) ) {
                baud = le32_to_cpu ( spcr->precise );
                if ( baud )
                        DBGC ( uart, "SPCR has precise baud rate %d\n", baud );
        }
        if ( ( ! baud ) && spcr->baud && ( spcr->baud < SPCR_BAUD_MAX ) ) {
                baud = ( SPCR_BAUD_BASE / spcr_baud_divisor[spcr->baud] );
                DBGC ( uart, "SPCR has baud rate %d\n", baud );
        }
        uart->baud = baud;

        /* Initialise according to type */
        switch ( spcr->type ) {
        case SPCR_TYPE_16550:
        case SPCR_TYPE_16450:
        case SPCR_TYPE_16550_GAS:
                if ( ( rc = spcr_16550 ( spcr, uart ) ) != 0 )
                        goto err_type;
                break;
        default:
                DBGC ( uart, "SPCR unsupported type %d\n", spcr->type );
                goto err_type;
        }

        return uart;

 err_type:
 err_table:
        /* Fall back to using fixed serial console */
        return fixed_serial_console();
}

PROVIDE_SERIAL ( spcr, default_serial_console, spcr_console );