Re: [PATCH] ARM: at91: debug: use DEBUG_UART_VIRT

Nicolas Ferre
2016-06-08T07:17:28Z

Le 07/06/2016 18:23, Alexandre Belloni a écrit :
> On 07/06/2016 at 17:48:21 +0200, Nicolas Ferre wrote :
>> Le 07/06/2016 17:24, Alexandre Belloni a écrit :
>>> AT91 still uses an offset (0x0100 0000) from the physical address to map
>>> the debug UART. This is unfortunate as for some platforms (sama5d3 and
>>> earlier), it ends up in the PCI zone and PCI is enabled in multi_v7.
>>> Switch to DEBUG_UART_VIRT to solve that.
>>>
>>> Tested on sama5d3 and 9g20.
>>>
>>> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
>>
>> People using their old defconfigs must pay attention to this change...
>> but it's true that it's a debug configuration anyway...
>>
>
> I really doubt people are letting DEBUG_LL enabled in a production
> kernel...
>
>>> diff --git a/arch/arm/include/debug/at91.S b/arch/arm/include/debug/at91.S
>>> index d4ae3b8e2426..0098401e5aeb 100644
>>> --- a/arch/arm/include/debug/at91.S
>>> +++ b/arch/arm/include/debug/at91.S
>>> @@ -9,14 +9,6 @@
>>> *
>>> */
>>>
>>> -#ifdef CONFIG_MMU
>>> -#define AT91_IO_P2V(x) ((x) - 0x01000000)
>>> -#else
>>> -#define AT91_IO_P2V(x) (x)
>>> -#endif
>>> -
>>> -#define AT91_DEBUG_UART_VIRT AT91_IO_P2V(CONFIG_DEBUG_UART_PHYS)
>>> -
>>> #define AT91_DBGU_SR (0x14) /* Status Register */
>>> #define AT91_DBGU_THR (0x1c) /* Transmitter Holding Register */
>>> #define AT91_DBGU_TXRDY (1 << 1) /* Transmitter Ready */
>>> @@ -24,7 +16,7 @@
>>>
>>> .macro addruart, rp, rv, tmp
>>> ldr \rp, =CONFIG_DEBUG_UART_PHYS @ System peripherals (phys address)
>>> - ldr \rv, =AT91_DEBUG_UART_VIRT @ System peripherals (virt address)
>>> + ldr \rv, =CONFIG_DEBUG_UART_VIRT @ System peripherals (virt address)
>>
>> Shouldn't we protect the use of this defined value with some
>> #warning "Beware the value CONFIG_DEBUG_UART_VIRT haven't been defined:
>> is it intentional"
>> or even #error?
>>
>> or something like that?
>>
>
> Well, those that are using this feature are supposed to know what they
> are doing. There is now protection for CONFIG_DEBUG_UART_PHYS anyway.

So, I know that developers are sensible people and know what they're
doing but still... what about having a protection for both anyway...
instead of silently crashing at runtime?

Bye,