linux/drivers/acpi/spcr.c

/*
 * Copyright (c) 2012, Intel Corporation
 * Copyright (c) 2015, Red Hat, Inc.
 * Copyright (c) 2015, 2016 Linaro Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) "ACPI: SPCR: " fmt

#include <linux/acpi.h>
#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/serial_core.h>

/*
 * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
 * occasionally getting stuck as 1. To avoid the potential for a hang, check
 * TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
 * implementations, so only do so if an affected platform is detected in
 * parse_spcr().
 */
bool qdf2400_e44_present;
EXPORT_SYMBOL(qdf2400_e44_present);

/*
 * Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
 * Detect them by examining the OEM fields in the SPCR header, similiar to PCI
 * quirk detection in pci_mcfg.c.
 */
static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
{
	if (memcmp(h->oem_id, "QCOM  ", ACPI_OEM_ID_SIZE))
		return false;

	if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
		return true;

	if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
			h->oem_revision == 1)
		return true;

	return false;
}

/*
 * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
 * register aligned to 32-bit. In addition, the BIOS also encoded the
 * access width to be 8 bits. This function detects this errata condition.
 */
static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
{
	if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
		return false;

	if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE))
		return false;

	if (!memcmp(tb->header.oem_table_id, "XGENESPC",
	    ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
		return true;

	return false;
}

/**
 * parse_spcr() - parse ACPI SPCR table and add preferred console
 *
 * @earlycon: set up earlycon for the console specified by the table
 *
 * For the architectures with support for ACPI, CONFIG_ACPI_SPCR_TABLE may be
 * defined to parse ACPI SPCR table.  As a result of the parsing preferred
 * console is registered and if @earlycon is true, earlycon is set up.
 *
 * When CONFIG_ACPI_SPCR_TABLE is defined, this function should be called
 * from arch initialization code as soon as the DT/ACPI decision is made.
 *
 */
int __init parse_spcr(bool earlycon)
{
	static char opts[64];
	struct acpi_table_spcr *table;
	acpi_status status;
	char *uart;
	char *iotype;
	int baud_rate;
	int err;

	if (acpi_disabled)
		return -ENODEV;

	status = acpi_get_table(ACPI_SIG_SPCR, 0,
				(struct acpi_table_header **)&table);

	if (ACPI_FAILURE(status))
		return -ENOENT;

	if (table->header.revision < 2) {
		err = -ENOENT;
		pr_err("wrong table version\n");
		goto done;
	}

	if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
		switch (table->serial_port.access_width) {
		default:
			pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
		case ACPI_ACCESS_SIZE_BYTE:
			iotype = "mmio";
			break;
		case ACPI_ACCESS_SIZE_WORD:
			iotype = "mmio16";
			break;
		case ACPI_ACCESS_SIZE_DWORD:
			iotype = "mmio32";
			break;
		}
	} else
		iotype = "io";

	switch (table->interface_type) {
	case ACPI_DBG2_ARM_SBSA_32BIT:
		iotype = "mmio32";
		/* fall through */
	case ACPI_DBG2_ARM_PL011:
	case ACPI_DBG2_ARM_SBSA_GENERIC:
	case ACPI_DBG2_BCM2835:
		uart = "pl011";
		break;
	case ACPI_DBG2_16550_COMPATIBLE:
	case ACPI_DBG2_16550_SUBSET:
		uart = "uart";
		break;
	default:
		err = -ENOENT;
		goto done;
	}

	switch (table->baud_rate) {
	case 3:
		baud_rate = 9600;
		break;
	case 4:
		baud_rate = 19200;
		break;
	case 6:
		baud_rate = 57600;
		break;
	case 7:
		baud_rate = 115200;
		break;
	default:
		err = -ENOENT;
		goto done;
	}

	/*
	 * If the E44 erratum is required, then we need to tell the pl011
	 * driver to implement the work-around.
	 *
	 * The global variable is used by the probe function when it
	 * creates the UARTs, whether or not they're used as a console.
	 *
	 * If the user specifies "traditional" earlycon, the qdf2400_e44
	 * console name matches the EARLYCON_DECLARE() statement, and
	 * SPCR is not used.  Parameter "earlycon" is false.
	 *
	 * If the user specifies "SPCR" earlycon, then we need to update
	 * the console name so that it also says "qdf2400_e44".  Parameter
	 * "earlycon" is true.
	 *
	 * For consistency, if we change the console name, then we do it
	 * for everyone, not just earlycon.
	 */
	if (qdf2400_erratum_44_present(&table->header)) {
		qdf2400_e44_present = true;
		if (earlycon)
			uart = "qdf2400_e44";
	}

	if (xgene_8250_erratum_present(table))
		iotype = "mmio32";

	snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
		 table->serial_port.address, baud_rate);

	pr_info("console: %s\n", opts);

	if (earlycon)
		setup_earlycon(opts);

	err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);

done:
	acpi_put_table((struct acpi_table_header *)table);
	return err;
}