[U-Boot] [PATCH v4 2/2] serial: bcm283x_mu: Detect disabled serial device

[Alexander Graf]

> Am 16.08.2016 um 05:30 schrieb Stephen Warren <swarren at wwwdotorg.org>:
> 
>> On 08/15/2016 09:48 AM, Alexander Graf wrote:
>> On the raspberry pi, you can disable the serial port to gain dynamic frequency
>> scaling which can get handy at times.
>> 
>> However, in such a configuration the serial controller gets its rx queue filled
>> up with zero bytes which then happily get transmitted on to whoever calls
>> getc() today.
>> 
>> This patch adds detection logic for that case by checking whether the RX pin is
>> mapped to GPIO15 and disables the mini uart if it is not mapped properly.
>> 
>> That way we can leave the driver enabled in the tree and can determine during
>> runtime whether serial is usable or not, having a single binary that allows for
>> uart and non-uart operation.
> 
> Acked-by: Stephen Warren <swarren at wwwdotorg.org>
> 
> Nits:
> 
> I'd hope for a core DM feature to disable statically created devices rather than re-implementing it per driver, so we don't have to re-invent this each time we need it. Still, we can refactor this later if it turns out to be more generally useful.
> 
> Perhaps a separate patch for the raw serial driver feature (serial_bcm283x_mu.h, serial_bcm283x_mu.c), and the board-specific logic (all the other files)?

I was thinking about it, but figured that these two lines of code are so heavily intertwined with the fact that you want to actually set the disabled property. So I decided against splitting them out - it wouldn't benefit readability, bisectability or revertability (which are the usual reasons for splitting patches).


Alex