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? > + > + 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? > + } > > err = setup_earlycon(buf); > if (err == -ENOENT || err == -EALREADY) -- With Best Regards, Andy Shevchenko -- 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
