On 03/22/2016 04:09 AM, Andy Shevchenko wrote: > On Tue, Mar 22, 2016 at 12:46 PM, Aleksey Makarov > <aleksey.makarov@xxxxxxxxxx> wrote: >> 'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port >> Console Redirection Table) [2] as a mandatory ACPI table that >> specifies the configuration of serial console. >> >> Parse this table, setup earlycon and enable the specified console. >> >> Thanks to Peter Hurley for explaining how this should work. >> >> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html >> [2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx >> > >> +++ b/drivers/acpi/spcr.c >> @@ -0,0 +1,102 @@ >> +/* >> + * 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> >> + >> +static bool init_earlycon; >> + >> +void __init init_spcr_earlycon(void) >> +{ >> + init_earlycon = true; >> +} >> + >> +int __init parse_spcr(void) >> +{ >> + static char opts[64]; >> + struct acpi_table_spcr *table; >> + acpi_size table_size; >> + acpi_status status; >> + char *uart; >> + char *iotype; >> + int baud_rate; >> + int err = 0; >> + >> + status = acpi_get_table_with_size(ACPI_SIG_SPCR, 0, >> + (struct acpi_table_header **)&table, >> + &table_size); >> + >> + if (ACPI_FAILURE(status)) >> + return -ENOENT; >> + >> + if (table->header.revision < 2) { >> + err = -EINVAL; >> + pr_err("wrong table version\n"); >> + goto done; >> + } >> + >> + iotype = (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) ? >> + "mmio" : "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; >> + } >> + >> + sprintf(opts, "%s,%s,0x%llx,%d", uart, iotype, >> + table->serial_port.address, baud_rate); > > You may use snprintf(), though my question here what would happen on > 32-bit kernel when you supply 64-bit address as an option? Yeah this should probably use %pa for the printf specifier. But note this exposes underlying bug in the earlycon support, because that was originally written without 32/64-mixed bitness in mind; ie., the address is parsed and handled as unsigned long in most places. >> + >> + pr_info("console: %s", opts); >> + >> + if (init_earlycon) >> + setup_earlycon(opts); >> + >> + err = add_preferred_console(uart, 0, opts + strlen(uart) + 1); >> + >> +done: >> + early_acpi_os_unmap_memory((void __iomem *)table, table_size); >> + return err; >> +} >> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c >> index d217366..ec030c9 100644 >> --- a/drivers/tty/serial/earlycon.c >> +++ b/drivers/tty/serial/earlycon.c >> @@ -22,6 +22,7 @@ >> #include <linux/sizes.h> >> #include <linux/of.h> >> #include <linux/of_fdt.h> >> +#include <linux/acpi.h> >> >> #ifdef CONFIG_FIX_EARLYCON_MEM >> #include <asm/fixmap.h> >> @@ -206,11 +207,15 @@ static int __init param_setup_earlycon(char *buf) >> int err; >> >> /* >> - * Just 'earlycon' is a valid param for devicetree earlycons; >> - * don't generate a warning from parse_early_params() in that case >> + * Just 'earlycon' is a valid param for devicetree and ACPI SPCR >> + * earlycons; don't generate a warning from parse_early_params() >> + * in that case >> */ >> - if (!buf || !buf[0]) >> - return early_init_dt_scan_chosen_serial(); >> + if (!buf || !buf[0]) { >> + init_spcr_earlycon(); > >> + early_init_dt_scan_chosen_serial(); >> + return 0; > > And you hide an error? Well, this is a little bit tricky because "earlycon" early parameter with missing /chosen/stdout-path node is no longer an error, since ACPI may be specifying the earlycon instead. Regards, Peter Hurley >> + } >> >> err = setup_earlycon(buf); >> if (err == -ENOENT || err == -EALREADY) > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
