Re: [Xen-devel] [PATCH v1] xen/serial: Return actual bytes stored in TX FIFO for OMAP

[Oleksandr Tyshchenko <oleksandr.tyshchenko@xxxxxxxxxxxxxxx>]

On Tue, Oct 27, 2015 at 1:33 PM, Oleksandr Tyshchenko
<oleksandr.tyshchenko@xxxxxxxxxxxxxxx> wrote:
> Hi, all.
> Although OMAP and 8250 compatible UARTs have a lot of common, they
> differs at least in configuration steps
> since OMAP UART has such thing as "register access mode", also OMAP
> UART has additional features and as a result a subset of additional
> registers.
>
> On Tue, Oct 27, 2015 at 1:15 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>> On 27/10/15 11:05, Jan Beulich wrote:
>>>>>> On 27.10.15 at 11:54, <julien.grall@xxxxxxxxxx> wrote:
>>>> On 27/10/15 10:50, Jan Beulich wrote:
>>>>>>>> On 27.10.15 at 11:36, <oleksandr.tyshchenko@xxxxxxxxxxxxxxx> wrote:
>>>>>> --- a/xen/include/xen/8250-uart.h
>>>>>> +++ b/xen/include/xen/8250-uart.h
>>>>>> @@ -143,6 +143,15 @@
>>>>>>  /* Supplementary control register */
>>>>>>  #define UART_OMAP_SCR     0x10
>>>>>
>>>>> I think this one is already misplaced here (as is the one in the context
>>>>> below the change).
>>>>
>>>> I don't think so, the omap UART is based on the 8250 and share some
>>>> common registers.
>>>
>>> Well, if it's that way then the patch is fine, but I then question why
>>> we have a separate omap-uart.c.
>>
>> I've got no clue, the omap is a superset of the 8250 and actually we
>> already use the 8250 low-level serial for those platforms.

The 8250 low-level serial (debug-8250.inc) is suitable for OMAP based platforms
since performs common 8250 things without any initialization and
interrupt handling
unlike full OMAP UART driver in XEN.

>>
>> Linux is also having a separate driver for the OMAP UART. Oleksandr, is
>> there any fundamental difference between the OMAP and ns16550 driver?

The differences I have mentioned above can we treat as fundamental?
And what are you suggesting about the patch? Create a separate OMAP
specific header?

Thank you.

>>
>> Regards,
>>
>> --
>> Julien Grall
>
>
>
> --
>
> Oleksandr Tyshchenko | Embedded Dev
> GlobalLogic
> www.globallogic.com



-- 

Oleksandr Tyshchenko | Embedded Dev
GlobalLogic
www.globallogic.com

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