[U-Boot] [PATCH v3] ns16550: change to allow 32 bit access to registers

[Dave Aldridge]

Hi Wolfgang

On 07/09/11 22:22, Wolfgang Denk wrote:
> Dear Dave Aldridge,
> 
> In message <1314877212-31552-1-git-send-email-fovsoft at gmail.com> you wrote:
>> If CONFIG_SYS_NS16550_MEM32 is defined then 32 bit memory
>> mapped access will be used to read/write the uart registers.
>>
>> This is especially useful for SoC devices that implement 16550
>> compatible uarts but that have peripheral access width constraints.
>>
>> Signed-off-by: Dave Aldridge <fovsoft at gmail.com>
> ...
> 
>> --- a/drivers/serial/ns16550.c
>> +++ b/drivers/serial/ns16550.c
>> @@ -19,6 +19,12 @@
>>  #ifdef CONFIG_SYS_NS16550_PORT_MAPPED
>>  #define serial_out(x,y)	outb(x,(ulong)y)
>>  #define serial_in(y)	inb((ulong)y)
>> +#elif defined(CONFIG_SYS_NS16550_MEM32) && (CONFIG_SYS_NS16550_REG_SIZE > 0)
>> +#define serial_out(x,y) out_be32(y,x)
>> +#define serial_in(y) 	in_be32(y)
>> +#elif defined(CONFIG_SYS_NS16550_MEM32) && (CONFIG_SYS_NS16550_REG_SIZE < 0)
>> +#define serial_out(x,y) out_le32(y,x)
>> +#define serial_in(y) 	in_le32(y)
> 
> Sorry for the dumb question, but in which way is REG_SIZE > 0 or
> REG_SIZE < 0 connected to the endianess of the target system?
> 
> My understanding is that this only defines how byte wide registers
> need to be padded, i. e. wether they are connected to the highest or
> to the lowest byte lane.  THis has nothing to do with the endianess of
> the system, and it appears wrong to me, to imply such a relation here.
> 
> Detlev, what do you think?
> 

No such thing as a dumb question. It is my understanding from the way that the
REG_SIZE macro is currently being used in the driver that the endianess of the
uart can be inferred in this way.

>>  #else
>>  #define serial_out(x,y) writeb(x,y)
>>  #define serial_in(y) 	readb(y)
>> diff --git a/include/ns16550.h b/include/ns16550.h
>> index 9ea81e9..d4ffac9 100644
>> --- a/include/ns16550.h
>> +++ b/include/ns16550.h
>> @@ -23,6 +23,8 @@
>>  
>>  #if !defined(CONFIG_SYS_NS16550_REG_SIZE) || (CONFIG_SYS_NS16550_REG_SIZE == 0)
>>  #error "Please define NS16550 registers size."
>> +#elif defined(CONFIG_SYS_NS16550_MEM32)
>> +#define UART_REG(x) unsigned int x;
> 
> I think you should rather use an explicit 32 bit data type here;
> "int" may be 64 bits on some systems.
> 
> Best regards,
> 
> Wolfgang Denk
> 

Cheers

Dave