[PATCH v2 1/4] tty: serial: Add 8250 earlycon to support noinit option

[peter@hurleysoftware.com (Peter Hurley)]

On 02/02/2015 12:33 AM, Eddie Huang wrote:
> Hi Peter,
> 
> On Sun, 2015-02-01 at 21:24 -0800, Greg Kroah-Hartman wrote:
>> On Mon, Feb 02, 2015 at 12:15:31AM -0500, Peter Hurley wrote:
>>> On 02/01/2015 11:28 PM, Greg Kroah-Hartman wrote:
>>>> On Sun, Feb 01, 2015 at 10:45:12PM -0500, Peter Hurley wrote:
>>>>> On 02/01/2015 10:16 PM, Eddie Huang wrote:
>>>
>>>>> I'll respin proper patches on top of Greg's tty-testing branch with reverts
>>>>> for the noinit options. I noticed that one of the noinit patches actually
>>>>> has the linkage for the mtk earlycon, so I'll be sure to preserve that.
>>>>
>>>> I can just drop the patches in the tty-testing branch, that's what it is
>>>> there for :)
>>>>
>>>> Just let me know the specific patches and I will do so, thanks.
>>>
>>> Well that pretty much means dropping the 3 patches that add earlycon to
>>> 8250_mtk and then applying my patch (needs fixed to apply cleanly, which
>>> I can do) and then applying a fixed-up replacement patch to add earlycon
>>> to 8250_mtk (which I can also supply).
>>>
>>> Is that the way you want to go?
>>
>> Sounds good to me, send your patch, and I'll fix it all up tomorrow.
>>
>> thanks,
>>
>> greg k-h
> 
> Actually, your patch is a little different from my original idea.
> Although my use case only care about divisor now, but other hardware
> setting is still hard-code, not from parameter. In init_port()
> function:   
> 	serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
> 	serial8250_early_out(port, UART_IER, 0);/* no interrupt */
> 	serial8250_early_out(port, UART_FCR, 0); /* no fifo */
> 	serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
> 
> This is why I propose a new option "noinit".
> 
> After checking further, in my case, I found that your patch should be
> unnecessary because if skip baudrate, probe_baud() read DLL/DLM register
> and init_port() write the same DLL/DLM value back, no touch any high
> speed register, which means keep uart divisor setting as loader
> 
> Since I don't take "console=uart,mmio32,<addr>,noinit" into
> consideration, it is good to drop my patches in the tty-testing branch.
> For my case, I can send another series without noinit, just 8250_mtk.c
> and its linkage modification in 8250_early.c

Ok.

Greg,

The patches to drop from tty-testing are:
* 405017d Document: Modify 8250 earlycon kernel parameters
* 0dff3a4 tty: serial: 8250_mtk: Add earlycon
* b829735 tty: serial: Add 8250 earlycon to support noinit option

Regards,
Peter Hurley