FreeBSD source tree https://cgit-dev.freebsd.org/src-test2/atom?h=release%2F5.3.0 2004-06-24T10:07:28Z 2004-06-24T10:07:28Z Poul-Henning Kamp phk@FreeBSD.org 2004-06-24T10:07:28Z urn:sha1:28710806cbb64a31d7b4afcba9523376bd0ca941 2003-09-17T03:11:32Z Marcel Moolenaar marcel@FreeBSD.org 2003-09-17T03:11:32Z urn:sha1:44ed791b92a2d5a5a2ec7dceeaac65e9749a8eda an UART interface could get stuck when a new interrupt condition arose while servicing a previous interrupt. Since an interrupt was already pending, no new interrupt would be triggered. Avoid infinite recursion by flushing the Rx FIFO and marking an overrun condition when we could not move the data from the Rx FIFO to the receive buffer in toto. Failure to flush the Rx FIFO would leave the Rx ready condition pending. Note that the SAB 82532 already did this due to the nature of the chip. 2003-09-17T01:41:21Z Marcel Moolenaar marcel@FreeBSD.org 2003-09-17T01:41:21Z urn:sha1:06287620b4f768f18a0874557b1cfa70e35791df precisely where locking would be needed before adding it, but it seems uart(4) draws slightly too much attention to have it without locking for too long. The lock added is a spinlock that protects access to the underlying hardware. As a first and obvious stab at this, each method of the hardware interface grabs the lock. Roughly speaking this serializes the methods. Exceptions are the probe, attach and detach methods. 2003-09-07T04:59:15Z Warner Losh imp@FreeBSD.org 2003-09-07T04:59:15Z urn:sha1:af1af2d2cce18446faaa0e7336b97d98dc39e287 (ns8250 copied and s/ns8250/i8251/g), but there for linkage purposes. Real code to follow, once I get past some boot issues on my pc98 boxes with recent current.