Subject: [PATCH v3 2/5] ACPI: parse SPCR and enable matching console

From: [email-masked] (Aleksey Makarov)
Date: Mon, 22 Feb 2016 18:03:19 +0300

Hi Yury,

Thank you for review/suggestions.  I will address it all in the next version except for...

On 02/21/2016 12:42 PM, Yury Norov wrote:
> On Mon, Feb 15, 2016 at 09:05:26PM +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 and check if any registered console match the
>> description.  If it does, enable that console.
>>
>> Introduce a new function acpi_console_check().  At the uart port
>> registration, this function checks if the ACPI SPCR table specifies
>> its argument of type struct uart_port to be a console
>> and if so calls add_preferred_console().
>>
>> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
>> [2] http://msdn.microsoft.com/en-us/library/windows/hardware/dn639131(v=vs.85).aspx
>>
>> Signed-off-by: Aleksey Makarov <[email-masked]>
>> ---
>>  drivers/acpi/Kconfig             |  3 ++
>>  drivers/acpi/Makefile            |  1 +
>>  drivers/acpi/spcr.c              | 97 ++++++++++++++++++++++++++++++++++++++++
>>  drivers/tty/serial/serial_core.c | 14 +++++-
>>  include/linux/acpi.h             | 10 +++++
>>  5 files changed, 123 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 346101c..708b143 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -81,6 +81,7 @@ 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..a1eca91
>> --- /dev/null
>> +++ b/drivers/acpi/spcr.c
>> @@ -0,0 +1,97 @@
>> +/*
>> + * 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 int acpi_table_parse_spcr(int (*handler)(struct acpi_table_spcr *table,
>> +						void *data), void *data)
>> +{
>> +	struct acpi_table_spcr *table = NULL;
> Hi Alexey,
> 
> Few minor comments...
> 
> Are you sure you need thin initialization?
> 
>> +	acpi_size table_size;
>> +	acpi_status status;
>> +	int err;
>> +
>> +	status = acpi_get_table_with_size(ACPI_SIG_SPCR, 0,
>> +					  (struct acpi_table_header **)&table,
>> +					  &table_size);
>> +
>> +	if (ACPI_FAILURE(status))
>> +		return -ENODEV;
>> +
>> +	err = handler(table, data);
>> +
>> +	early_acpi_os_unmap_memory(table, table_size);
>> +
>> +	return err;
>> +}
>> +
>> +static int spcr_table_handler_check(struct acpi_table_spcr *table, void *data)
> 
> The name of function is not clear for me.
> You're not only checking here, but also
> adding console. 
> 
>> +{
>> +	struct uart_port *uport = data;
>> +	char *options;
>> +
>> +	if (table->header.revision < 2)
>> +		return -EOPNOTSUPP;
>> +
>> +	switch (table->baud_rate) {
> 
> You don't need 'options' if your big condition returns false,
> so you can evaluate it inside conditional block.
> 
>> +	case 3:
>> +		options = "9600";
>> +		break;
>> +	case 4:
>> +		options = "19200";
>> +		break;
>> +	case 6:
>> +		options = "57600";
>> +		break;
>> +	case 7:
>> +		options = "115200";
>> +		break;
>> +	default:
>> +		options = "";
>> +		break;
> 
> 'break' isnot needed here

... except for this.

No, it is not, but C language style guides tell us to have it here.
Also see the first example from Documentation/CodingStyle 
where they have it.

Thank you
Aleksey Makarov

> 
>> +	}
>> +
>> +	if ((table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY &&
> 
> Nitpick: just for better readability, I'd split it onto a set of
> separated checks:
> 
>         foo() {
>                 if (!cond1)
>                         return 0;
> 
>                 if (!cond2)
>                         return 0;
>                 ...
> 
>                 switch () {
>                 case 1:
>                         ...
>                 case 2:
>                         ...
>                 case 3:
>                         ...
>                 default:
>                         ...
>                 }
>                 
>                 return 1;
>         }
> 
>> +	     table->serial_port.address == (u64)uport->mapbase) ||
>> +	    (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_IO &&
>> +	     table->serial_port.address == (u64)uport->iobase)) {
>> +		pr_info("adding preferred console [%s%d]\n", uport->cons->name,
>> +			uport->line);
>> +		add_preferred_console(uport->cons->name, uport->line, options);
>> +		return 1;
>> +
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * acpi_console_check - Check if uart matches the console specified by SPCR.
>> + *
>> + * @uport:	uart port to check
>> + *
>> + * This function checks if the ACPI SPCR table specifies @uport to be a console
>> + * and if so calls add_preferred_console()
>> + *
>> + * Return: a non-error value if the console matches.
>> + */
>> +bool acpi_console_check(struct uart_port *uport)
>> +{
>> +	if (acpi_disabled || console_set_on_cmdline)
>> +		return false;
>> +
>> +	return acpi_table_parse_spcr(spcr_table_handler_check, uport) > 0;
>> +}
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index a126a60..459ab54 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -34,6 +34,7 @@
>>  #include <linux/serial_core.h>
>>  #include <linux/delay.h>
>>  #include <linux/mutex.h>
>> +#include <linux/acpi.h>
>>  
>>  #include <asm/irq.h>
>>  #include <asm/uaccess.h>
>> @@ -2654,8 +2655,17 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
>>  		spin_lock_init(&uport->lock);
>>  		lockdep_set_class(&uport->lock, &port_lock_key);
>>  	}
>> -	if (uport->cons && uport->dev)
>> -		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
>> +
>> +	/*
>> +	 * Support both open FW and ACPI access to console definitions.
>> +	 * Both of_console_check() and acpi_console_check() will call
>> +	 * add_preferred_console() if a console definition is found.
>> +	 */
>> +	if (uport->cons && uport->dev) {
>> +		if (!acpi_console_check(uport))
>> +			of_console_check(uport->dev->of_node, uport->cons->name,
>> +					 uport->line);
>> +	}
>>  
>>  	uart_configure_port(drv, state, uport);
>>  
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index 06ed7e5..ea0c297 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -1004,4 +1004,14 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
>>  #define acpi_probe_device_table(t)	({ int __r = 0; __r;})
>>  #endif
>>  
>> +struct uart_port;
>> +#ifdef CONFIG_ACPI_SPCR_TABLE
>> +bool acpi_console_check(struct uart_port *uport);
>> +#else
>> +static inline bool acpi_console_check(struct uart_port *uport)
>> +{
>> +	return FALSE;
>> +}
>> +#endif
>> +
>>  #endif	/*_LINUX_ACPI_H*/
>> -- 
>> 2.7.1
>>
>>
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