int __init acpi_parse_spcr()

in spcr.c [87:231]

• 104 lines of code
• 27 McCabe index (conditional complexity)

int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
{
	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)
		pr_info("SPCR table version %d\n", table->header.revision);

	if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
		u32 bit_width = table->serial_port.access_width;

		if (bit_width > ACPI_ACCESS_BIT_MAX) {
			pr_err("Unacceptable wide SPCR Access Width.  Defaulting to byte size\n");
			bit_width = ACPI_ACCESS_BIT_DEFAULT;
		}
		switch (ACPI_ACCESS_BIT_WIDTH((bit_width))) {
		default:
			pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
			fallthrough;
		case 8:
			iotype = "mmio";
			break;
		case 16:
			iotype = "mmio16";
			break;
		case 32:
			iotype = "mmio32";
			break;
		}
	} else
		iotype = "io";

	switch (table->interface_type) {
	case ACPI_DBG2_ARM_SBSA_32BIT:
		iotype = "mmio32";
		fallthrough;
	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:
	case ACPI_DBG2_16550_WITH_GAS:
		uart = "uart";
		break;
	default:
		err = -ENOENT;
		goto done;
	}

	switch (table->baud_rate) {
	case 0:
		/*
		 * SPCR 1.04 defines 0 as a preconfigured state of UART.
		 * Assume firmware or bootloader configures console correctly.
		 */
		baud_rate = 0;
		break;
	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 (enable_earlycon)
			uart = "qdf2400_e44";
	}

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

		/* for xgene v1 and v2 we don't know the clock rate of the
		 * UART so don't attempt to change to the baud rate state
		 * in the table because driver cannot calculate the dividers
		 */
		baud_rate = 0;
	}

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

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

	if (enable_earlycon)
		setup_earlycon(opts);

	if (enable_console)
		err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
	else
		err = 0;
done:
	acpi_put_table((struct acpi_table_header *)table);
	return err;
}