On 03/22/2016 05:26 AM, Yury Norov wrote: > On Tue, Mar 22, 2016 at 01:46:30PM +0300, Aleksey Makarov 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 >> >> Signed-off-by: Aleksey Makarov <aleksey.makarov@xxxxxxxxxx> >> --- >> drivers/acpi/Kconfig | 3 ++ >> drivers/acpi/Makefile | 1 + >> drivers/acpi/spcr.c | 102 ++++++++++++++++++++++++++++++++++++++++++ >> drivers/tty/serial/earlycon.c | 13 ++++-- >> include/linux/acpi.h | 8 ++++ >> 5 files changed, 123 insertions(+), 4 deletions(-) >> create mode 100644 drivers/acpi/spcr.c >> >> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig >> index 65fb483..5611eb6 100644 >> --- a/drivers/acpi/Kconfig >> +++ b/drivers/acpi/Kconfig >> @@ -77,6 +77,9 @@ config ACPI_DEBUGGER_USER >> >> endif >> >> +config ACPI_SPCR_TABLE >> + bool >> + >> config ACPI_SLEEP >> bool >> depends on SUSPEND || HIBERNATION >> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile >> index 7395928..f70ae14 100644 >> --- a/drivers/acpi/Makefile >> +++ b/drivers/acpi/Makefile >> @@ -82,6 +82,7 @@ obj-$(CONFIG_ACPI_EC_DEBUGFS) += ec_sys.o >> obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o >> obj-$(CONFIG_ACPI_BGRT) += bgrt.o >> obj-$(CONFIG_ACPI_CPPC_LIB) += cppc_acpi.o >> +obj-$(CONFIG_ACPI_SPCR_TABLE) += spcr.o >> obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o >> >> # processor has its own "processor." module_param namespace >> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c >> new file mode 100644 >> index 0000000..1ec82f9 >> --- /dev/null >> +++ 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; >> +} >> + > > 1. I see you keep in mind multiple access. Concurrent access is not a concern here: only the boot cpu is running and intrs are off. The "init_earlycon" flag is used because parsing the "earlycon" early param is earlier than parsing ACPI tables. Then you'd worry about race > conditions as well. In this case, I'd consider atomic access to > variable. > 2. It seems you need is_init() helper too. > >> +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; > > You can do not initialize 'err'. Why? > >> + >> + 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); > > As 'opts' is static, don't you need to take some measures to prevent > concurrent access. The simpler measure for me is to declare it on > stack. Again, concurrent access is not a concern at this early time. Regards, Peter Hurley >> + >> + 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; >> + } >> >> err = setup_earlycon(buf); >> if (err == -ENOENT || err == -EALREADY) >> diff --git a/include/linux/acpi.h b/include/linux/acpi.h >> index 06ed7e5..ebbb212 100644 >> --- a/include/linux/acpi.h >> +++ b/include/linux/acpi.h >> @@ -1004,4 +1004,12 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev, >> #define acpi_probe_device_table(t) ({ int __r = 0; __r;}) >> #endif >> >> +#ifdef CONFIG_ACPI_SPCR_TABLE >> +int parse_spcr(void); >> +void init_spcr_earlycon(void); >> +#else >> +static inline int parse_spcr(void) { return 0; } >> +static inline void init_spcr_earlycon(void) {} >> +#endif >> + >> #endif /*_LINUX_ACPI_H*/ >> -- >> 2.7.4 -- 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
