-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Somebody in the thread at some point said:
| The overrun does seem to correlate to times where one would logically | assume that IRQs may be held off, but I don't have enough data-points to | know for certain. | | Of course, hardware flow-control is supposed to fix this so that we | don't have to worry about latency for the serial IRQ -- but that's the | part that's not working. So the need is to handle the worst case: I see. I understand what you meant about wondering if the GSM side honours the flow control now. | We cannot slow the GSM; it is transmitting at 115200 baud. The best we | can do with the S3C2410 UART is to generate the RX IRQ when the FIFO | reaches 4 characters; that leaves 12 characters before overrun. That's | a latency of 1.0 milliseconds -- I'd call that real-time. | | | So, as I understand it, the FIQ is the only solution to meet this need, | but the FIQ is already in-use on the GTA02. I'm not sure where we go | from here... FIQ will typically come in at < 1us latency FWIW. The FIQ is only lightly used actually, so as not to eat power the bulk of the time no FIQs occur. Only when we want to do something like read the battery state it runs a timer to cause FIQs. At all other times it doesn't hurt if the FIQ source is something different since no timer events will come. What we could do to enforce a solution is to set the FIQ source to the UART interrupt when not in use for timer-driven function, but either way we can check UART interrupt status at the start of the FIQ ISR. So even when it is triggered off timer asynchronously to UART activity, we will be basically polling at 20 - 100us period. But the other side of it integrating the UART data captured this way into the normal serial driver architecture might be a bit messy :-) - -Andy -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iEYEARECAAYFAkgV8ZwACgkQOjLpvpq7dMpHvwCdG1LsxEglXtljfk9YRSHyvDKB 9rMAn1nYEAGqlca03jCkEgy5CzDbG0sy =QQ2H -----END PGP SIGNATURE-----
