Re: [Xen-devel] [PATCH v5 2/5] xen/arm: add 8250 compatible UART support for early_printk

[Chen Baozi <baozich@xxxxxxxxx>]

On Aug 8, 2013, at 8:17 PM, Chen Baozi <baozich@xxxxxxxxx> wrote:

> 
> On Aug 8, 2013, at 8:06 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> 
>> On 08/08/2013 01:04 PM, Chen Baozi wrote:
>>> 
>>> On Aug 8, 2013, at 7:36 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>>> 
>>>> On Thu, 2013-08-08 at 12:34 +0100, Ian Campbell wrote:
>>>> 
>>>>>> diff --git a/xen/include/xen/8250-uart.h b/xen/include/xen/8250-uart.h
>>>>>> index 7287364..33daa6d 100644
>>>>>> --- a/xen/include/xen/8250-uart.h
>>>>>> +++ b/xen/include/xen/8250-uart.h
>>>>>> @@ -22,6 +22,10 @@
>>>>>> #ifndef __XEN_8250_UART_H__
>>>>>> #define __XEN_8250_UART_H__
>>>>>> 
>>>>>> +#ifdef CONFIG_ARM
>>>>>> +#define REG_SHIFT         2
>>>>>> +#endif
>>>>> 
>>>>> I think this should actually be part of the per-platform early-printk
>>>>> block, e.g. EARLY_UART_REG_SHIFT
>>>> 
>>>> I should have also said that for non-early drivers this should come from
>>>> the device tree.
>>>> 
>>>> Possibly in the case of your OMAP speciifc driver it could be hardcoded,
>>>> but only if it isn't in DT IMHO.
>>> 
>>> It seems OMAP5's DT doesn't have this info? Does exynos5 have it?
>> 
>> Exynos5 uses a different UART which doesn't need shift.
> 
> I don't think DT would hold that info. (Fix me if I'm wrong.) Actually this 
> shift
> comes from the different register size between OMAP UART (32-bit) and common 
> 8250
> UART (8-bit). And we would like to share the offset macros between the two 
> similar
> UART. For those UART doesn't share offset macros with others or they do have 
> same
> register size, the shift is not necessary.

Maybe we can put REG_SHIFT into arch/arm/arm32/debug-8250.inc and 
drivers/char/omap-uart.c
rather than the header?
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel