It looks like we're going to use com(4) on armv7 after all. Given
that we have a device tree there, we have a pretty good idea what UART
type we're driving. So we should be able to avoid the flaky probing
code in com(4). Here is a diff that makes the driver only do the
probing if the uart type was set to COM_UART_UNKNOWN at the start.
This is the default if you don't explicitly set it in the bus glue
part of the driver. There are a few bits of glue code that do set te
uart type. Of those only arch/octeon/dev/cn30xxuart.c sets it to a
value that makes com(4) go through the probing codepath.
Can somebody verify that this diff doesn't break octeon?
Thanks,
Mark
Index: dev/ic/com.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/com.c,v
retrieving revision 1.158
diff -u -p -r1.158 com.c
--- dev/ic/com.c 14 Sep 2014 14:17:24 -0000 1.158
+++ dev/ic/com.c 15 Aug 2016 21:23:58 -0000
@@ -1583,6 +1583,7 @@ com_attach_subr(struct com_softc *sc)
{
bus_space_tag_t iot = sc->sc_iot;
bus_space_handle_t ioh = sc->sc_ioh;
+ int probe = 0;
u_int8_t lcr;
sc->sc_ier = 0;
@@ -1616,7 +1617,7 @@ com_attach_subr(struct com_softc *sc)
/*
* Skip specific probes if attachment code knows it already.
*/
- if (sc->sc_uarttype == COM_UART_UNKNOWN)
+ if (sc->sc_uarttype == COM_UART_UNKNOWN) {
switch (bus_space_read_1(iot, ioh, com_iir) >> 6) {
case 0:
sc->sc_uarttype = COM_UART_16450;
@@ -1631,8 +1632,11 @@ com_attach_subr(struct com_softc *sc)
sc->sc_uarttype = COM_UART_UNKNOWN;
break;
}
+ probe = 1;
+ }
- if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for ST16650s */
+ /* Probe for ST16650s */
+ if (probe && sc->sc_uarttype == COM_UART_16550A) {
bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
if (bus_space_read_1(iot, ioh, com_efr) == 0) {
bus_space_write_1(iot, ioh, com_efr, EFR_CTS);
@@ -1647,7 +1651,8 @@ com_attach_subr(struct com_softc *sc)
}
#if 0 /* until com works with large FIFOs */
- if (sc->sc_uarttype == COM_UART_ST16650V2) { /* Probe for XR16850s */
+ /* Probe for XR16850s */
+ if (probe && sc->sc_uarttype == COM_UART_ST16650V2) {
u_int8_t dlbl, dlbh;
/* Enable latch access and get the current values. */
@@ -1670,7 +1675,8 @@ com_attach_subr(struct com_softc *sc)
}
#endif
- if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for TI16750s */
+ /* Probe for TI16750s */
+ if (probe && sc->sc_uarttype == COM_UART_16550A) {
bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
bus_space_write_1(iot, ioh, com_fifo,
FIFO_ENABLE | FIFO_ENABLE_64BYTE);
@@ -1686,7 +1692,9 @@ com_attach_subr(struct com_softc *sc)
/* Reset the LCR (latch access is probably enabled). */
bus_space_write_1(iot, ioh, com_lcr, lcr);
- if (sc->sc_uarttype == COM_UART_16450) { /* Probe for 8250 */
+
+ /* Probe for 8250 */
+ if (probe && sc->sc_uarttype == COM_UART_16450) {
u_int8_t scr0, scr1, scr2;
scr0 = bus_space_read_1(iot, ioh, com_scratch);
