Subject: [PATCH v7 3/5] ACPI: parse SPCR and enable matching console

From: [email-masked] (Peter Hurley)
Date: Mon, 4 Apr 2016 14:23:45 -0700

On 03/31/2016 06:40 AM, 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.
> 
> Defer initialization of DT earlycon until ACPI/DT decision is made.
> 
> Parse the ACPI SPCR table, setup earlycon if required,
> enable 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

So for the code:

Reviewed-by: Peter Hurley <[email-masked]>

However, I still have concerns regarding the license of this code
as GPL, when the Microsoft patent notice in [2] above only provides
two license options, neither of which are referred to in the
drivers/acpi/spcr.c file header and neither of which (I believe) are
GPL compatible.

> Signed-off-by: Aleksey Makarov <[email-masked]>
> ---
>  drivers/acpi/Kconfig          |   3 ++
>  drivers/acpi/Makefile         |   1 +
>  drivers/acpi/spcr.c           | 111 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/tty/serial/earlycon.c |  19 +++++++-
>  include/linux/acpi.h          |   6 +++
>  include/linux/serial_core.h   |   6 +++
>  6 files changed, 144 insertions(+), 2 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..68ffc33
> --- /dev/null
> +++ b/drivers/acpi/spcr.c
> @@ -0,0 +1,111 @@
> +/*
> + * 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>
> +
> +/**
> + * 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 should be called
> + * from arch inintialization 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_size table_size;
> +	acpi_status status;
> +	char *uart;
> +	char *iotype;
> +	int baud_rate;
> +	int err;
> +
> +	if (acpi_disabled)
> +		return -ENODEV;
> +
> +	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 = -ENOENT;
> +		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;
> +	}
> +
> +	snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
> +		 table->serial_port.address, baud_rate);
> +
> +	pr_info("console: %s", opts);
> +
> +	if (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 7aae655..ea00b9f 100644
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -21,6 +21,7 @@
>  #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>
> @@ -199,6 +200,14 @@ int __init setup_earlycon(char *buf)
>  	return -ENOENT;
>  }
>  
> +/*
> + * When CONFIG_ACPI_SPCR_TABLE is defined, "earlycon" without parameters in
> + * command line does not start DT earlycon immediately, instead it defers
> + * starting it until DT/ACPI decision is made.  At that time if ACPI is enabled
> + * call parse_spcr(), else call early_init_dt_scan_chosen_stdout()
> + */
> +bool earlycon_init_is_deferred __initdata;
> +
>  /* early_param wrapper for setup_earlycon() */
>  static int __init param_setup_earlycon(char *buf)
>  {
> @@ -208,8 +217,14 @@ static int __init param_setup_earlycon(char *buf)
>  	 * Just 'earlycon' is a valid param for devicetree earlycons;
>  	 * don't generate a warning from parse_early_params() in that case
>  	 */
> -	if (!buf || !buf[0])
> -		return early_init_dt_scan_chosen_stdout();
> +	if (!buf || !buf[0]) {
> +		if (IS_ENABLED(CONFIG_ACPI_SPCR_TABLE)) {
> +			earlycon_init_is_deferred = true;
> +			return 0;
> +		} else {
> +			return early_init_dt_scan_chosen_stdout();
> +		}
> +	}
>  
>  	err = setup_earlycon(buf);
>  	if (err == -ENOENT || err == -EALREADY)
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 06ed7e5..1095ed6 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1004,4 +1004,10 @@ 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(bool earlycon);
> +#else
> +static inline int parse_spcr(bool earlycon) { return 0; }
> +#endif
> +
>  #endif	/*_LINUX_ACPI_H*/
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index cbfcf38..de6750f 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -363,6 +363,12 @@ extern int of_setup_earlycon(const struct earlycon_id *match,
>  			     unsigned long node,
>  			     const char *options);
>  
> +#ifdef CONFIG_SERIAL_EARLYCON
> +extern bool earlycon_init_is_deferred __initdata;
> +#else
> +static const bool earlycon_init_is_deferred;
> +#endif
> +
>  struct uart_port *uart_get_console(struct uart_port *ports, int nr,
>  				   struct console *c);
>  int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
>