1 files changed, 12 insertions, 2 deletions

diff --git a/sys/dev/pccbb/pccbb_pci.c b/sys/dev/pccbb/pccbb_pci.c
index 7dca418249fb..cf9b17f93744 100644
--- a/sys/dev/pccbb/pccbb_pci.c
+++ b/sys/dev/pccbb/pccbb_pci.c
@@ -502,10 +502,19 @@ cbb_chipinit(struct cbb_softc *sc)
 		 * properly initialized.
 		 *
 		 * The TI125X parts have a different register.
+		 *
+		 * Note: Only the lower two nibbles matter. When set
+		 * to 0, the MFUNC{0,1} pins are GPIO, which isn't
+		 * going to work out too well because we specifically
+		 * program these parts to parallel interrupt signalling
+		 * elsewhere. We preserve the upper bits of this
+		 * register since changing them have subtle side effects
+		 * for different variants of the card and are
+		 * extremely difficult to exaustively test.
 		 */
 		mux = pci_read_config(sc->dev, CBBR_MFUNC, 4);
 		sysctrl = pci_read_config(sc->dev, CBBR_SYSCTRL, 4);
-		if (mux == 0) {
+		if ((mux & (CBBM_MFUNC_PIN0 | CBBM_MFUNC_PIN1)) == 0) {
 			mux = (mux & ~CBBM_MFUNC_PIN0) |
 			    CBBM_MFUNC_PIN0_INTA;
 			if ((sysctrl & CBBM_SYSCTRL_INTRTIE) == 0)
@@ -518,7 +527,8 @@ cbb_chipinit(struct cbb_softc *sc)
 		/*
 		 * Disable zoom video.  Some machines initialize this
 		 * improperly and exerpience has shown that this helps
-		 * prevent strange behavior.
+		 * prevent strange behavior. We don't support zoom
+		 * video anyway, so no harm can come from this.
 		 */
 		pci_write_config(sc->dev, CBBR_MMCTRL, 0, 4);
 		break;