asmc: prefer MMIO backend over PIO when both are present

T2, T1, and some pre-T1 Macs advertise a legacy PIO
range in the SMC ACPI _CRS alongside a live MMIO window, but the
silicon behind the PIO range is bogus.

Try MMIO first, validate via LDKN >= 2, fall back to PIO if that
fails or no MMIO resource is present. Drop "(T2)" from the backend
message since MMIO isn't T2-exclusive.

MFC: 1 week
Reviewed by:	ngie
Differential Revision:	https://reviews.freebsd.org/D58839

(cherry picked from commit 37826269b41b46c72264191d35b09baf24e055b9)

2 files changed, 11 insertions, 9 deletions

diff --git a/sys/dev/asmc/asmc.c b/sys/dev/asmc/asmc.c
index d55c585419fb..80412b9c8daf 100644
--- a/sys/dev/asmc/asmc.c
+++ b/sys/dev/asmc/asmc.c
@@ -427,25 +427,22 @@ asmc_probe(device_t dev)
 }
 
 /*
- * Try PIO first; fall back to MMIO for T2 Macs.
+ * Try MMIO first; the legacy PIO range can be claimable but dead.
+ * Fall back to PIO if MMIO probe fails or the resource is absent.
  */
 static int
 asmc_try_probe(device_t dev)
 {
 	struct asmc_softc *sc = device_get_softc(dev);
 
-	sc->sc_ioport = bus_alloc_resource_any(dev, SYS_RES_IOPORT,
-	    &sc->sc_rid_port, RF_ACTIVE);
-	if (sc->sc_ioport != NULL)
-		return (0);
-
 	sc->sc_rid_mem = 0;
 	sc->sc_iomem = bus_alloc_resource_any(dev, SYS_RES_MEMORY,
 	    &sc->sc_rid_mem, RF_ACTIVE);
 	if (sc->sc_iomem != NULL) {
 		if (asmc_mmio_probe(dev) == 0) {
 			sc->sc_is_mmio = true;
-			device_printf(dev, "using MMIO backend (T2)\n");
+			if (bootverbose)
+				device_printf(dev, "using MMIO backend\n");
 			return (0);
 		}
 		bus_release_resource(dev, SYS_RES_MEMORY,
@@ -453,7 +450,12 @@ asmc_try_probe(device_t dev)
 		sc->sc_iomem = NULL;
 	}
 
-	device_printf(dev, "unable to allocate IO port\n");
+	sc->sc_ioport = bus_alloc_resource_any(dev, SYS_RES_IOPORT,
+	    &sc->sc_rid_port, RF_ACTIVE);
+	if (sc->sc_ioport != NULL)
+		return (0);
+
+	device_printf(dev, "unable to allocate IO port or MMIO\n");
 	return (ENOMEM);
 }
 
diff --git a/sys/dev/asmc/asmcmmio.c b/sys/dev/asmc/asmcmmio.c
index 237e8ec4ed52..4981822c4723 100644
--- a/sys/dev/asmc/asmcmmio.c
+++ b/sys/dev/asmc/asmcmmio.c
@@ -292,7 +292,7 @@ asmc_mmio_probe(device_t dev)
 		return (ENXIO);
 	}
 
-	device_printf(dev, "MMIO: LDKN=%d, T2 SMC detected\n", ldkn);
+	device_printf(dev, "MMIO: LDKN=%d, MMIO-capable SMC detected\n", ldkn);
 	sc->sc_is_t2 = 1;
 
 	return (0);