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

From: [email-masked] (Peter Hurley)
Date: Fri, 19 Feb 2016 08:13:38 -0800

On 02/19/2016 02:47 AM, Aleksey Makarov wrote:
> Hi Peter,
> 
> Thank you for review.
> 
> On 02/19/2016 01:19 AM, Peter Hurley wrote:
>> On 02/15/2016 10:05 AM, Aleksey Makarov wrote:
> 
> [..]
> 
>>> 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);
>>
>> of_console_check() is not a good model for enabling a console.
>> It's a hack with several shortcomings (and bugs) that is tolerated here
>> because of its broad applicability to a wide range of platforms and drivers.
> 
> It's definitely not the best code I saw 

> but there is no bugs.

I pointed out just one of the problems with adding a preferred console
late in the boot cycle (eg, at uart driver load) in the other patch review.

>> I specifically added console matching to enable exactly this kind of
>> console-selection-via-firmware. Please use that facility.
> 
> I described why this does not work (except you insist on having 
> new made up names for all types of SPCR consoles) in the reply to another your message.

They're not "new made up names".

They're the documented names of earlycons, which you'd know if you
researched how you're going to start an earlycon with the DBG2 table
like I suggested in previous reviews.

And I explained in the other patch review exactly how it works.

Regards,
Peter Hurley

>>> +	}
>>>  
>>>  	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*/
>>>
>>