powerpc/pmac/smp: Fix CPU hotplug crashes on some machines

On some machines that use i2c to synchronize the timebases (such
as PowerMac7,2/7,3 G5 machines), hotplug CPU would crash when
putting back a new CPU online due to the underlying i2c bus being
closed.

This uses the newly added bringup_done() callback to move the close
along with other housekeeping calls, and adds a CPU notifier to
re-open the i2c bus around subsequent hotplug operations

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 55 insertions, 16 deletions

diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c
index 837989e72ca1..74a43c652041 100644
--- a/arch/powerpc/platforms/powermac/smp.c
+++ b/arch/powerpc/platforms/powermac/smp.c
@@ -840,30 +840,68 @@ static void __devinit smp_core99_setup_cpu(int cpu_nr)
 
         /* Setup openpic */
         mpic_setup_this_cpu();
+}
 
-        if (cpu_nr == 0) {
-#ifdef CONFIG_PPC64
-                extern void g5_phy_disable_cpu1(void);
+#ifdef CONFIG_HOTPLUG_CPU
+static int smp_core99_cpu_notify(struct notifier_block *self,
+                                 unsigned long action, void *hcpu)
+{
+        int rc;
 
-                /* Close i2c bus if it was used for tb sync */
+        switch(action) {
+        case CPU_UP_PREPARE:
+        case CPU_UP_PREPARE_FROZEN:
+                /* Open i2c bus if it was used for tb sync */
                 if (pmac_tb_clock_chip_host) {
-                        pmac_i2c_close(pmac_tb_clock_chip_host);
-                        pmac_tb_clock_chip_host = NULL;
+                        rc = pmac_i2c_open(pmac_tb_clock_chip_host, 1);
+                        if (rc) {
+                                pr_err("Failed to open i2c bus for time sync\n");
+                                return notifier_from_errno(rc);
+                        }
                 }
+                break;
+        case CPU_ONLINE:
+        case CPU_UP_CANCELED:
+                /* Close i2c bus if it was used for tb sync */
+                if (pmac_tb_clock_chip_host)
+                        pmac_i2c_close(pmac_tb_clock_chip_host);
+                break;
+        default:
+                break;
+        }
+        return NOTIFY_OK;
+}
 
-                /* If we didn't start the second CPU, we must take
-                 * it off the bus
-                 */
-                if (of_machine_is_compatible("MacRISC4") &&
-                    num_online_cpus() < 2)              
-                        g5_phy_disable_cpu1();
-#endif /* CONFIG_PPC64 */
+static struct notifier_block __cpuinitdata smp_core99_cpu_nb = {
+        .notifier_call  = smp_core99_cpu_notify,
+};
+#endif /* CONFIG_HOTPLUG_CPU */
 
-                if (ppc_md.progress)
-                        ppc_md.progress("core99_setup_cpu 0 done", 0x349);
+static void __init smp_core99_bringup_done(void)
+{
+#ifdef CONFIG_PPC64
+        extern void g5_phy_disable_cpu1(void);
+
+        /* Close i2c bus if it was used for tb sync */
+        if (pmac_tb_clock_chip_host)
+                pmac_i2c_close(pmac_tb_clock_chip_host);
+
+        /* If we didn't start the second CPU, we must take
+         * it off the bus.
+         */
+        if (of_machine_is_compatible("MacRISC4") &&
+            num_online_cpus() < 2) {
+                set_cpu_present(1, false);
+                g5_phy_disable_cpu1();
         }
-}
+#endif /* CONFIG_PPC64 */
 
+#ifdef CONFIG_HOTPLUG_CPU
+        register_cpu_notifier(&smp_core99_cpu_nb);
+#endif
+        if (ppc_md.progress)
+                ppc_md.progress("smp_core99_bringup_done", 0x349);
+}
 
 #ifdef CONFIG_HOTPLUG_CPU
 
@@ -940,6 +978,7 @@ static void pmac_cpu_die(void)
 struct smp_ops_t core99_smp_ops = {
         .message_pass   = smp_mpic_message_pass,
         .probe          = smp_core99_probe,
+        .bringup_done   = smp_core99_bringup_done,
         .kick_cpu       = smp_core99_kick_cpu,
         .setup_cpu      = smp_core99_setup_cpu,
         .give_timebase  = smp_core99_give_timebase,