# Re: \[PATCH\] Powerpc 8xx CPM\_UART delay in receive

- From: Alan Cox \<hidden\>
- Date: 2012-08-16 14:25:09 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2012/08/3909454
- Thread: https://ratatoskr.run/linux-serial/2012/08/3908106/t.md

```text
> The PowerPC CPM is working differently. It doesn't use a fifo but 
> buffers. Buffers are handed to the microprocessor only when they are 
> full or after a timeout period which is adjustable. In the driver, the 

Which is different how - remembering we empty the FIFO on an IRQ

> buffers are configured with a size of 32 bytes. And the timeout is set 
> to the size of the buffer. That is this timeout that I'm reducing to 1 
> byte in my proposed patch. I can't see what it would break for high 
> speed I/O.

How can a timeout be measured in "bytes". Can we have a bit more clarity
on how the hardware works and take it from there ?

Alan
```