linux-kernel - Re: [PATCH v2 2/3] serial: 8250_early: prepare for dynamic BASE

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Date:	Mon, 05 Jan 2015 08:33:59 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"robh@...nel.org" <robh@...nel.org>,
	"jslaby@...e.cz" <jslaby@...e.cz>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 2/3] serial: 8250_early: prepare for dynamic BASE_BAUD

On 01/05/2015 08:21 AM, Vineet Gupta wrote:
> Hi Peter,
> 
> On Monday 05 January 2015 06:31 PM, Peter Hurley wrote:
>> Hi Vineet,
>>
>> On 01/05/2015 06:30 AM, Vineet Gupta wrote:
>>> -	port->uartclk = BASE_BAUD * 16;
>>> +	port->uartclk = earlycon_base_baud(options) * 16;
>> I don't understand why BASE_BAUD can't be defined by arc as arc_earlycon_base_baud().
>> Why is the weak binding necessary?
> 
> Indeed weak semantics are not really needed - even now we have what u r suggesting
> - the missing part was existing conditional definition which will simply go away
> if I implement the fdt parsing in that singly defined function. Thx for the tip :-)
> 
> In that case this requires no change to driver and I can fixup the platform -
> perhaps ur Ack on next version will be nice.

Will do.

> Also what do u think of the early IER optimization ?

Seems ok except the commit changelog is wrong: IER is disabled twice per _line_.
How did you profile it? It's ok if the answer is "seemed faster"; I'm just
curious.

Regards,
Peter Hurley

>> I'm pushing back on this because port initialization (and especially 8250)
>> is already a ridiculous spiderweb.
> 
> I totally agree.
> 
> Thx,
> -Vineet
> 
>>
>> Regards,
>> Peter Hurley
>>
>>>  	options = strchr(options, ',');
>>>  	if (options) {
>>> @@ -156,7 +165,7 @@ int __init of_setup_earlycon(unsigned long addr,
>>>  
>>>  	port->iotype = UPIO_MEM;
>>>  	port->mapbase = addr;
>>> -	port->uartclk = BASE_BAUD * 16;
>>> +	port->uartclk = earlycon_base_baud(NULL) * 16;
>>>  	port->membase = earlycon_map(addr, SZ_4K);
>>>  
>>>  	early_console_dev.con->data = &early_console_dev;
>>>
>>
> 

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