Messages in this thread | | | Subject | Re: [PATH RESEND v2 03/10] tty: xuartps: Always enable transmitter in start_tx | From | Peter Hurley <> | Date | Fri, 20 Nov 2015 12:12:29 -0500 |
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On 11/20/2015 12:05 PM, Sören Brinkmann wrote: > On Fri, 2015-11-20 at 07:13AM -0500, Peter Hurley wrote: >> >> >> On 11/19/2015 03:02 PM, Soren Brinkmann wrote: >>> start_tx must start transmitting characters. Regardless of the state of >>> the circular buffer, always enable the transmitter hardware. >> >> Why? >> >> Does cdns_uart_stop_tx() actually stop the transmitter so that >> data remains in the transmitter? > > Fixing up the patch, I looked at this one. It might actually do that.
Ok.
> Without having changed anything. The doc says: "The driver should > stop transmitting characters as soon as possible.". And the > implementation is really not draining any FIFO, but just disabling the > transmitter. I take your question as that this might not be this way? > Should stop_tx drain the FIFO first?
No.
Most h/w can't actually stop the transmitter (or not without losing data), so that's why the expectation is only for "as soon as possible". Stopping sooner is better.
Regards, Peter Hurley
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