svn commit: r194679 - in head/sys: conf powerpc/conf
powerpc/cpufreq powerpc/powermac
Nathan Whitehorn
nwhitehorn at FreeBSD.org
Tue Jun 23 04:28:33 UTC 2009
Author: nwhitehorn
Date: Tue Jun 23 04:28:32 2009
New Revision: 194679
URL: http://svn.freebsd.org/changeset/base/194679
Log:
Add cpufreq support on the PowerPC G5, along with a skeleton SMU driver
in order to slew CPU voltage during frequency changes. The OpenBSD SMU
driver was an extremely helpful reference for this.
Added:
head/sys/powerpc/cpufreq/pcr.c (contents, props changed)
head/sys/powerpc/powermac/smu.c (contents, props changed)
Modified:
head/sys/conf/files.powerpc
head/sys/powerpc/conf/GENERIC
head/sys/powerpc/conf/NOTES
Modified: head/sys/conf/files.powerpc
==============================================================================
--- head/sys/conf/files.powerpc Tue Jun 23 04:02:36 2009 (r194678)
+++ head/sys/conf/files.powerpc Tue Jun 23 04:28:32 2009 (r194679)
@@ -99,6 +99,7 @@ powerpc/booke/swtch.S optional e500
powerpc/booke/trap.c optional e500
powerpc/booke/vm_machdep.c optional e500
powerpc/cpufreq/dfs.c optional cpufreq
+powerpc/cpufreq/pcr.c optional cpufreq aim
powerpc/fpu/fpu_add.c optional fpu_emu
powerpc/fpu/fpu_compare.c optional fpu_emu
powerpc/fpu/fpu_div.c optional fpu_emu
@@ -127,18 +128,19 @@ powerpc/ofw/ofw_syscons.c optional sc ai
powerpc/powermac/ata_kauai.c optional powermac ata | powermac atamacio
powerpc/powermac/ata_macio.c optional powermac ata | powermac atamacio
powerpc/powermac/ata_dbdma.c optional powermac ata | powermac atamacio
+powerpc/powermac/cuda.c optional powermac cuda
+powerpc/powermac/cpcht.c optional powermac pci
powerpc/powermac/dbdma.c optional powermac pci
powerpc/powermac/grackle.c optional powermac pci
powerpc/powermac/hrowpic.c optional powermac pci
powerpc/powermac/kiic.c optional powermac kiic
+powerpc/powermac/macgpio.c optional powermac pci
powerpc/powermac/macio.c optional powermac pci
powerpc/powermac/openpic_macio.c optional powermac pci
powerpc/powermac/pswitch.c optional powermac pswitch
-powerpc/powermac/uninorth.c optional powermac pci
-powerpc/powermac/cuda.c optional powermac cuda
powerpc/powermac/pmu.c optional powermac pmu
-powerpc/powermac/macgpio.c optional powermac pci
-powerpc/powermac/cpcht.c optional powermac pci
+powerpc/powermac/smu.c optional powermac smu
+powerpc/powermac/uninorth.c optional powermac pci
powerpc/powermac/vcoregpio.c optional powermac
powerpc/powerpc/altivec.c optional aim
powerpc/powerpc/atomic.S standard
Modified: head/sys/powerpc/conf/GENERIC
==============================================================================
--- head/sys/powerpc/conf/GENERIC Tue Jun 23 04:02:36 2009 (r194678)
+++ head/sys/powerpc/conf/GENERIC Tue Jun 23 04:28:32 2009 (r194679)
@@ -158,6 +158,7 @@ device fwe # Ethernet over FireWire (n
# Misc
device powermac_nvram # Open Firmware configuration NVRAM
+device smu # Apple System Management Unit
# ADB support
device adb
Modified: head/sys/powerpc/conf/NOTES
==============================================================================
--- head/sys/powerpc/conf/NOTES Tue Jun 23 04:02:36 2009 (r194678)
+++ head/sys/powerpc/conf/NOTES Tue Jun 23 04:28:32 2009 (r194679)
@@ -33,6 +33,7 @@ device ofwd # Open Firmware disks
device adb # Apple Desktop Bus
device cuda # VIA-CUDA ADB interface
device pmu # Apple Power Management Unit
+device smu # Apple System Management Unit
device snd_ai2s # Apple I2S Audio
device snd_davbus # Apple Davbus Audio
Added: head/sys/powerpc/cpufreq/pcr.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/sys/powerpc/cpufreq/pcr.c Tue Jun 23 04:28:32 2009 (r194679)
@@ -0,0 +1,333 @@
+/*-
+ * Copyright (c) 2009 Nathan Whitehorn
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/cpu.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+
+#include <dev/ofw/ofw_bus.h>
+
+#include "cpufreq_if.h"
+
+struct pcr_softc {
+ device_t dev;
+ uint32_t pcr_vals[3];
+ int nmodes;
+};
+
+static void pcr_identify(driver_t *driver, device_t parent);
+static int pcr_probe(device_t dev);
+static int pcr_attach(device_t dev);
+static int pcr_settings(device_t dev, struct cf_setting *sets, int *count);
+static int pcr_set(device_t dev, const struct cf_setting *set);
+static int pcr_get(device_t dev, struct cf_setting *set);
+static int pcr_type(device_t dev, int *type);
+
+static device_method_t pcr_methods[] = {
+ /* Device interface */
+ DEVMETHOD(device_identify, pcr_identify),
+ DEVMETHOD(device_probe, pcr_probe),
+ DEVMETHOD(device_attach, pcr_attach),
+
+ /* cpufreq interface */
+ DEVMETHOD(cpufreq_drv_set, pcr_set),
+ DEVMETHOD(cpufreq_drv_get, pcr_get),
+ DEVMETHOD(cpufreq_drv_type, pcr_type),
+ DEVMETHOD(cpufreq_drv_settings, pcr_settings),
+
+ {0, 0}
+};
+
+static driver_t pcr_driver = {
+ "pcr",
+ pcr_methods,
+ sizeof(struct pcr_softc)
+};
+
+static devclass_t pcr_devclass;
+DRIVER_MODULE(pcr, cpu, pcr_driver, pcr_devclass, 0, 0);
+
+/*
+ * States
+ */
+
+#define PCR_TO_FREQ(a) ((a >> 17) & 3)
+
+#define PCR_FULL 0
+#define PCR_HALF 1
+#define PCR_QUARTER 2 /* Only on 970MP */
+
+#define PSR_RECEIVED (1ULL << 61)
+#define PSR_COMPLETED (1ULL << 61)
+
+/*
+ * SCOM addresses
+ */
+
+#define SCOM_PCR 0x0aa00100 /* Power Control Register */
+#define SCOM_PCR_BIT 0x80000000 /* Data bit for PCR */
+#define SCOM_PSR 0x40800100 /* Power Status Register */
+
+/*
+ * SCOM Glue
+ */
+
+#define SCOMC_READ 0x00008000
+#define SCOMC_WRITE 0x00000000
+
+static void
+write_scom(register_t address, uint64_t value)
+{
+ register_t msr;
+ register_t hi, lo, scratch;
+
+ hi = (value >> 32) & 0xffffffff;
+ lo = value & 0xffffffff;
+
+ msr = mfmsr();
+ mtmsr(msr & ~PSL_EE); isync();
+
+ mtspr64(SPR_SCOMD, hi, lo, scratch);
+ isync();
+ mtspr(SPR_SCOMC, address | SCOMC_WRITE);
+ isync();
+
+ mtmsr(msr); isync();
+}
+
+static uint64_t
+read_scom(register_t address)
+{
+ register_t msr;
+ uint64_t ret;
+
+ msr = mfmsr();
+ mtmsr(msr & ~PSL_EE); isync();
+
+ mtspr(SPR_SCOMC, address | SCOMC_READ);
+ isync();
+
+ __asm __volatile ("mfspr %0,%1;"
+ " mr %0+1, %0; srdi %0,%0,32" : "=r" (ret) : "K" (SPR_SCOMD));
+
+ (void)mfspr(SPR_SCOMC); /* Complete transcation */
+
+ mtmsr(msr); isync();
+
+ return (ret);
+}
+
+static void
+pcr_identify(driver_t *driver, device_t parent)
+{
+ uint16_t vers;
+ vers = mfpvr() >> 16;
+
+ /* Check for an IBM 970-class CPU */
+ switch (vers) {
+ case IBM970FX:
+ case IBM970GX:
+ case IBM970MP:
+ break;
+ default:
+ return;
+ }
+
+ /* Make sure we're not being doubly invoked. */
+ if (device_find_child(parent, "pcr", -1) != NULL)
+ return;
+
+ /*
+ * We attach a child for every CPU since settings need to
+ * be performed on every CPU in the SMP case.
+ */
+ if (BUS_ADD_CHILD(parent, 10, "pcr", -1) == NULL)
+ device_printf(parent, "add pcr child failed\n");
+}
+
+static int
+pcr_probe(device_t dev)
+{
+ if (resource_disabled("pcr", 0))
+ return (ENXIO);
+
+ device_set_desc(dev, "PPC 970 Power Control Register");
+ return (0);
+}
+
+static int
+pcr_attach(device_t dev)
+{
+ struct pcr_softc *sc;
+ phandle_t cpu;
+ uint32_t modes[3];
+ int i;
+
+ sc = device_get_softc(dev);
+ sc->dev = dev;
+
+ cpu = ofw_bus_get_node(device_get_parent(dev));
+
+ if (cpu <= 0) {
+ device_printf(dev,"No CPU device tree node!\n");
+ return (ENXIO);
+ }
+
+ /*
+ * Collect the PCR values for each mode from the device tree.
+ * These include bus timing information, and so cannot be
+ * directly computed.
+ */
+ sc->nmodes = OF_getproplen(cpu, "power-mode-data");
+ if (sc->nmodes <= 0 || sc->nmodes > sizeof(sc->pcr_vals)) {
+ device_printf(dev,"No power mode data in device tree!\n");
+ return (ENXIO);
+ }
+ OF_getprop(cpu, "power-mode-data", modes, sc->nmodes);
+ sc->nmodes /= sizeof(modes[0]);
+
+ /* Sort the modes */
+ for (i = 0; i < sc->nmodes; i++)
+ sc->pcr_vals[PCR_TO_FREQ(modes[i])] = modes[i];
+
+ cpufreq_register(dev);
+ return (0);
+}
+
+static int
+pcr_settings(device_t dev, struct cf_setting *sets, int *count)
+{
+ struct pcr_softc *sc;
+
+ sc = device_get_softc(dev);
+ if (sets == NULL || count == NULL)
+ return (EINVAL);
+ if (*count < sc->nmodes)
+ return (E2BIG);
+
+ /* Return a list of valid settings for this driver. */
+ memset(sets, CPUFREQ_VAL_UNKNOWN, sizeof(*sets) * sc->nmodes);
+
+ sets[0].freq = 10000; sets[0].dev = dev;
+ sets[1].freq = 5000; sets[1].dev = dev;
+ if (sc->nmodes > 2)
+ sets[2].freq = 2500; sets[2].dev = dev;
+ *count = sc->nmodes;
+
+ return (0);
+}
+
+static int
+pcr_set(device_t dev, const struct cf_setting *set)
+{
+ struct pcr_softc *sc;
+ register_t pcr, msr;
+ uint64_t psr;
+
+ if (set == NULL)
+ return (EINVAL);
+ sc = device_get_softc(dev);
+
+ /* Construct the new PCR */
+
+ pcr = SCOM_PCR_BIT;
+
+ if (set->freq == 10000)
+ pcr |= sc->pcr_vals[0];
+ else if (set->freq == 5000)
+ pcr |= sc->pcr_vals[1];
+ else if (set->freq == 2500)
+ pcr |= sc->pcr_vals[2];
+
+ msr = mfmsr();
+ mtmsr(msr & ~PSL_EE); isync();
+
+ /* 970MP requires PCR and PCRH to be cleared first */
+
+ write_scom(SCOM_PCR,0); /* Clear PCRH */
+ write_scom(SCOM_PCR,SCOM_PCR_BIT); /* Clear PCR */
+
+ /* Set PCR */
+
+ write_scom(SCOM_PCR, pcr);
+
+ /* Wait for completion */
+
+ do {
+ DELAY(100);
+ psr = read_scom(SCOM_PSR);
+ } while ((psr & PSR_RECEIVED) && !(psr & PSR_COMPLETED));
+
+ mtmsr(msr); isync();
+
+ return (0);
+}
+
+static int
+pcr_get(device_t dev, struct cf_setting *set)
+{
+ struct pcr_softc *sc;
+ uint64_t psr;
+
+ if (set == NULL)
+ return (EINVAL);
+ sc = device_get_softc(dev);
+
+ memset(set, CPUFREQ_VAL_UNKNOWN, sizeof(*set));
+
+ psr = read_scom(SCOM_PSR);
+
+ /* We want bits 6 and 7 */
+ psr = (psr >> 56) & 3;
+
+ set->freq = 10000;
+ if (psr == PCR_HALF)
+ set->freq = 5000;
+ else if (psr == PCR_QUARTER)
+ set->freq = 2500;
+
+ set->dev = dev;
+
+ return (0);
+}
+
+static int
+pcr_type(device_t dev, int *type)
+{
+
+ if (type == NULL)
+ return (EINVAL);
+
+ *type = CPUFREQ_TYPE_RELATIVE;
+ return (0);
+}
+
Added: head/sys/powerpc/powermac/smu.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/sys/powerpc/powermac/smu.c Tue Jun 23 04:28:32 2009 (r194679)
@@ -0,0 +1,288 @@
+/*-
+ * Copyright (c) 2009 Nathan Whitehorn
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/bus.h>
+#include <sys/systm.h>
+#include <sys/module.h>
+#include <sys/conf.h>
+#include <sys/cpu.h>
+#include <sys/kernel.h>
+#include <sys/rman.h>
+#include <sys/sysctl.h>
+
+#include <machine/bus.h>
+#include <machine/md_var.h>
+
+#include <dev/ofw/openfirm.h>
+#include <dev/ofw/ofw_bus.h>
+#include <powerpc/powermac/macgpiovar.h>
+
+struct smu_cmd {
+ uint8_t cmd;
+ uint8_t len;
+ uint8_t data[254];
+};
+
+struct smu_softc {
+ device_t sc_dev;
+ struct mtx sc_mtx;
+
+ struct resource *sc_memr;
+ int sc_memrid;
+
+ bus_dma_tag_t sc_dmatag;
+ bus_space_tag_t sc_bt;
+ bus_space_handle_t sc_mailbox;
+
+ struct smu_cmd *sc_cmd;
+ bus_addr_t sc_cmd_phys;
+ bus_dmamap_t sc_cmd_dmamap;
+};
+
+/* regular bus attachment functions */
+
+static int smu_probe(device_t);
+static int smu_attach(device_t);
+
+/* cpufreq notification hooks */
+
+static void smu_cpufreq_pre_change(device_t, const struct cf_level *level);
+static void smu_cpufreq_post_change(device_t, const struct cf_level *level);
+
+/* where to find the doorbell GPIO */
+
+static device_t smu_doorbell = NULL;
+
+static device_method_t smu_methods[] = {
+ /* Device interface */
+ DEVMETHOD(device_probe, smu_probe),
+ DEVMETHOD(device_attach, smu_attach),
+ { 0, 0 },
+};
+
+static driver_t smu_driver = {
+ "smu",
+ smu_methods,
+ sizeof(struct smu_softc)
+};
+
+static devclass_t smu_devclass;
+
+DRIVER_MODULE(smu, nexus, smu_driver, smu_devclass, 0, 0);
+
+#define SMU_MAILBOX 0x860c
+
+/* Command types */
+#define SMU_POWER 0xaa
+
+static int
+smu_probe(device_t dev)
+{
+ const char *name = ofw_bus_get_name(dev);
+
+ if (strcmp(name, "smu") != 0)
+ return (ENXIO);
+
+ device_set_desc(dev, "Apple System Management Unit");
+ return (0);
+}
+
+static void
+smu_phys_callback(void *xsc, bus_dma_segment_t *segs, int nsegs, int error)
+{
+ struct smu_softc *sc = xsc;
+
+ sc->sc_cmd_phys = segs[0].ds_addr;
+}
+
+static int
+smu_attach(device_t dev)
+{
+ struct smu_softc *sc;
+
+ sc = device_get_softc(dev);
+
+ mtx_init(&sc->sc_mtx, "smu", NULL, MTX_DEF);
+
+ /*
+ * Map the mailbox area. This should be determined from firmware,
+ * but I have not found a simple way to do that.
+ */
+ bus_dma_tag_create(NULL, 16, 0, BUS_SPACE_MAXADDR_32BIT,
+ BUS_SPACE_MAXADDR, NULL, NULL, PAGE_SIZE, 1, PAGE_SIZE, 0, NULL,
+ NULL, &(sc->sc_dmatag));
+ sc->sc_bt = &bs_be_tag;
+ bus_space_map(sc->sc_bt, SMU_MAILBOX, 4, 0, &sc->sc_mailbox);
+
+ /*
+ * Allocate the command buffer. This can be anywhere in the low 4 GB
+ * of memory.
+ */
+ bus_dmamem_alloc(sc->sc_dmatag, (void **)&sc->sc_cmd, BUS_DMA_WAITOK |
+ BUS_DMA_ZERO, &sc->sc_cmd_dmamap);
+ bus_dmamap_load(sc->sc_dmatag, sc->sc_cmd_dmamap,
+ sc->sc_cmd, PAGE_SIZE, smu_phys_callback, sc, 0);
+
+ /*
+ * Set up handlers to change CPU voltage when CPU frequency is changed.
+ */
+ EVENTHANDLER_REGISTER(cpufreq_pre_change, smu_cpufreq_pre_change, dev,
+ EVENTHANDLER_PRI_ANY);
+ EVENTHANDLER_REGISTER(cpufreq_post_change, smu_cpufreq_post_change, dev,
+ EVENTHANDLER_PRI_ANY);
+
+ return (0);
+}
+
+static int
+smu_run_cmd(device_t dev, struct smu_cmd *cmd)
+{
+ struct smu_softc *sc;
+ int doorbell_ack, result;
+
+ sc = device_get_softc(dev);
+
+ mtx_lock(&sc->sc_mtx);
+
+ /* Copy the command to the mailbox */
+ memcpy(sc->sc_cmd, cmd, sizeof(*cmd));
+ bus_dmamap_sync(sc->sc_dmatag, sc->sc_cmd_dmamap, BUS_DMASYNC_PREWRITE);
+ bus_space_write_4(sc->sc_bt, sc->sc_mailbox, 0, sc->sc_cmd_phys);
+
+ /* Invalidate the cacheline it is in -- SMU bypasses the cache */
+ __asm __volatile("dcbst 0,%0; sync" :: "r"(sc->sc_cmd): "memory");
+
+ /* Ring SMU doorbell */
+ macgpio_write(smu_doorbell, GPIO_DDR_OUTPUT);
+
+ /* Wait for the doorbell GPIO to go high, signaling completion */
+ do {
+ /* XXX: timeout */
+ DELAY(50);
+ doorbell_ack = macgpio_read(smu_doorbell);
+ } while (!doorbell_ack);
+
+ /* Check result. First invalidate the cache again... */
+ __asm __volatile("dcbf 0,%0; sync" :: "r"(sc->sc_cmd) : "memory");
+
+ bus_dmamap_sync(sc->sc_dmatag, sc->sc_cmd_dmamap, BUS_DMASYNC_POSTREAD);
+
+ /* SMU acks the command by inverting the command bits */
+ if (sc->sc_cmd->cmd == ~cmd->cmd)
+ result = 0;
+ else
+ result = EIO;
+
+ mtx_unlock(&sc->sc_mtx);
+
+ return (result);
+}
+
+static void
+smu_slew_cpu_voltage(device_t dev, int to)
+{
+ struct smu_cmd cmd;
+
+ cmd.cmd = SMU_POWER;
+ cmd.len = 8;
+ cmd.data[0] = 'V';
+ cmd.data[1] = 'S';
+ cmd.data[2] = 'L';
+ cmd.data[3] = 'E';
+ cmd.data[4] = 'W';
+ cmd.data[5] = 0xff;
+ cmd.data[6] = 1;
+ cmd.data[7] = to;
+
+ smu_run_cmd(dev, &cmd);
+}
+
+static void
+smu_cpufreq_pre_change(device_t dev, const struct cf_level *level)
+{
+ /*
+ * Make sure the CPU voltage is raised before we raise
+ * the clock.
+ */
+
+ if (level->rel_set[0].freq == 10000 /* max */)
+ smu_slew_cpu_voltage(dev, 0);
+}
+
+static void
+smu_cpufreq_post_change(device_t dev, const struct cf_level *level)
+{
+ /* We are safe to reduce CPU voltage after a downward transition */
+
+ if (level->rel_set[0].freq < 10000 /* max */)
+ smu_slew_cpu_voltage(dev, 1); /* XXX: 1/4 voltage for 970MP? */
+}
+
+/* Routines for probing the SMU doorbell GPIO */
+static int doorbell_probe(device_t dev);
+static int doorbell_attach(device_t dev);
+
+static device_method_t doorbell_methods[] = {
+ /* Device interface */
+ DEVMETHOD(device_probe, doorbell_probe),
+ DEVMETHOD(device_attach, doorbell_attach),
+ { 0, 0 },
+};
+
+static driver_t doorbell_driver = {
+ "smudoorbell",
+ doorbell_methods,
+ 0
+};
+
+static devclass_t doorbell_devclass;
+
+DRIVER_MODULE(smudoorbell, macgpio, doorbell_driver, doorbell_devclass, 0, 0);
+
+static int
+doorbell_probe(device_t dev)
+{
+ const char *name = ofw_bus_get_name(dev);
+
+ if (strcmp(name, "smu-doorbell") != 0)
+ return (ENXIO);
+
+ device_set_desc(dev, "SMU Doorbell GPIO");
+ device_quiet(dev);
+ return (0);
+}
+
+static int
+doorbell_attach(device_t dev)
+{
+ smu_doorbell = dev;
+ return (0);
+}
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