[src/trunk]: src/sys/dev/ic Fix hang up writing /dev/console rarely in specif...

[knakahara <knakahara%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/817888ef8f6e
branches:  trunk
changeset: 372563:817888ef8f6e
user:      knakahara <knakahara%NetBSD.org@localhost>
date:      Thu Dec 08 09:08:49 2022 +0000

description:
Fix hang up writing /dev/console rarely in specific environments.

Some BMC seems to require these syncronous operations.  If not,
it does not send transmit completion interrupts for some reason.

diffstat:

 sys/dev/ic/com.c |  36 +++++++++++++++++++++++++++++-------
 1 files changed, 29 insertions(+), 7 deletions(-)

diffs (91 lines):

diff -r 64bbe61483ce -r 817888ef8f6e sys/dev/ic/com.c
--- a/sys/dev/ic/com.c  Thu Dec 08 08:14:28 2022 +0000
+++ b/sys/dev/ic/com.c  Thu Dec 08 09:08:49 2022 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: com.c,v 1.380 2022/12/03 11:28:38 skrll Exp $ */
+/* $NetBSD: com.c,v 1.381 2022/12/08 09:08:49 knakahara Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2004, 2008 The NetBSD Foundation, Inc.
@@ -70,7 +70,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: com.c,v 1.380 2022/12/03 11:28:38 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: com.c,v 1.381 2022/12/08 09:08:49 knakahara Exp $");
 
 #include "opt_com.h"
 #include "opt_ddb.h"
@@ -206,6 +206,28 @@
        .cn_pri = CN_NORMAL
 };
 
+#define        CSR_WRITE_1_SYNC(r, o, v)       do {                    \
+               CSR_WRITE_1(r, o, v);                           \
+               switch(o) {                                     \
+               case COM_REG_IER:                               \
+                       (void)CSR_READ_1(r, COM_REG_IIR);       \
+                       break;                                  \
+               case COM_REG_TXDATA:                            \
+                       (void)CSR_READ_1(r, COM_REG_TLR);       \
+                       break;                                  \
+               }                                               \
+       } while(0)
+#define        CSR_WRITE_MULTI_SYNC(r, o, p, n)        do {            \
+               CSR_WRITE_MULTI(r, o, p, n);                    \
+               switch(o) {                                     \
+               case COM_REG_IER:                               \
+                       (void)CSR_READ_1(r, COM_REG_IIR);       \
+                       break;                                  \
+               case COM_REG_TXDATA:                            \
+                       (void)CSR_READ_1(r, COM_REG_TLR);       \
+                       break;                                  \
+               }                                               \
+       } while(0)
 
 const struct cdevsw com_cdevsw = {
        .d_open = comopen,
@@ -1961,7 +1983,7 @@
        /* Enable transmit completion interrupts if necessary. */
        if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
                SET(sc->sc_ier, IER_ETXRDY);
-               CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
+               CSR_WRITE_1_SYNC(regsp, COM_REG_IER, sc->sc_ier);
        }
 
        /* Output the first chunk of the contiguous buffer. */
@@ -1971,7 +1993,7 @@
                n = sc->sc_tbc;
                if (n > sc->sc_fifolen)
                        n = sc->sc_fifolen;
-               CSR_WRITE_MULTI(regsp, COM_REG_TXDATA, sc->sc_tba, n);
+               CSR_WRITE_MULTI_SYNC(regsp, COM_REG_TXDATA, sc->sc_tba, n);
                sc->sc_tbc -= n;
                sc->sc_tba += n;
        }
@@ -2359,7 +2381,7 @@
                                        CLR(sc->sc_ier, IER_ERXRDY);
                                        break;
                                }
-                               CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
+                               CSR_WRITE_1_SYNC(regsp, COM_REG_IER, sc->sc_ier);
                        }
                } else {
                        if ((iir & (IIR_RXRDY|IIR_TXRDY)) == IIR_RXRDY) {
@@ -2443,14 +2465,14 @@
                        n = sc->sc_tbc;
                        if (n > sc->sc_fifolen)
                                n = sc->sc_fifolen;
-                       CSR_WRITE_MULTI(regsp, COM_REG_TXDATA, sc->sc_tba, n);
+                       CSR_WRITE_MULTI_SYNC(regsp, COM_REG_TXDATA, sc->sc_tba, n);
                        sc->sc_tbc -= n;
                        sc->sc_tba += n;
                } else {
                        /* Disable transmit completion interrupts if necessary. */
                        if (ISSET(sc->sc_ier, IER_ETXRDY)) {
                                CLR(sc->sc_ier, IER_ETXRDY);
-                               CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
+                               CSR_WRITE_1_SYNC(regsp, COM_REG_IER, sc->sc_ier);
                        }
                        if (sc->sc_tx_busy) {
                                sc->sc_tx_busy = 0;