[U-Boot] [PATCH v6 07/10] ns16550: map register base address for debug UART

[Daniel Schwierzeck]

2016-01-04 14:07 GMT+01:00 Thomas Chou <thomas at wytron.com.tw>:
> Hi Wills,
>
>
> On 2016年01月04日 19:14, Wills Wang wrote:
>>
>> MIPS need to use KSEG1 address for register operation, this patch
>> add map_physmem to convert CONFIG_DEBUG_UART_BASE for debug UART.
>>
>> Signed-off-by: Wills Wang <wills.wang at live.com>
>> ---
>>
>> Changes in v6: None
>> Changes in v5: None
>> Changes in v4: None
>> Changes in v3: None
>> Changes in v2: None
>>
>>   drivers/serial/ns16550.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
>> index 3b24af0..1e2538e 100644
>> --- a/drivers/serial/ns16550.c
>> +++ b/drivers/serial/ns16550.c
>> @@ -270,7 +270,8 @@ int NS16550_tstc(NS16550_t com_port)
>>
>>   static inline void _debug_uart_init(void)
>>   {
>> -       struct NS16550 *com_port = (struct NS16550
>> *)CONFIG_DEBUG_UART_BASE;
>> +       struct NS16550 *com_port = (struct NS16550 *)map_physmem(
>> +                               CONFIG_DEBUG_UART_BASE, 0, MAP_NOCACHE);
>>         int baud_divisor;
>>
>>         /*
>> @@ -293,7 +294,8 @@ static inline void _debug_uart_init(void)
>>
>>   static inline void _debug_uart_putc(int ch)
>>   {
>> -       struct NS16550 *com_port = (struct NS16550
>> *)CONFIG_DEBUG_UART_BASE;
>> +       struct NS16550 *com_port = (struct NS16550 *)map_physmem(
>> +                               CONFIG_DEBUG_UART_BASE, 0, MAP_NOCACHE);
>>
>>         while (!(serial_din(&com_port->lsr) & UART_LSR_THRE))
>>                 ;
>>
>
> As debug uart may be used in very early stage and SPL, I would suggest the
> CONFIG_DEBUG_UART_BASE here is mapped to uncached space already. So that we
> can keep the code and stack usage minimal.
>
> My concern is that the uncache mapping in nios2 arch is different between
> NOMMU and MMU core, which will be decoded from device tree. So it won't work
> for nios2 until DM initialized.
>
> Naked-by: Thomas Chou <thomas at wytron.com.tw>
>

I agree with Thomas. Please set CONFIG_DEBUG_UART_BASE to a KSEG1
address and discard this patch.

-- 
- Daniel