powerpc/powernv: Return secondary CPUs to firmware on kexec

With OPAL v3 we can return secondary CPUs to firmware on kexec. This
allows firmware to do various cleanups making things generally more
reliable, and will enable the "new" kernel to call OPAL to perform
some reconfiguration tasks early on that can only be done while
all the CPUs are in firmware.

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

3 files changed, 14 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 48ad6780c6d9..c5cd72833d6e 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -128,6 +128,7 @@ extern int opal_enter_rtas(struct rtas_args *args,
 #define OPAL_XSCOM_WRITE                        66
 #define OPAL_LPC_READ                           67
 #define OPAL_LPC_WRITE                          68
+#define OPAL_RETURN_CPU                         69
 
 #ifndef __ASSEMBLY__
 
@@ -646,6 +647,7 @@ int64_t opal_set_system_attention_led(uint8_t led_action);
 int64_t opal_pci_next_error(uint64_t phb_id, uint64_t *first_frozen_pe,
                             uint16_t *pci_error_type, uint16_t *severity);
 int64_t opal_pci_poll(uint64_t phb_id);
+int64_t opal_return_cpu(void);
 
 int64_t opal_xscom_read(uint32_t gcid, uint32_t pcb_addr, uint64_t *val);
 int64_t opal_xscom_write(uint32_t gcid, uint32_t pcb_addr, uint64_t val);
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index 42c06fba3994..8f3844535fbb 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -115,3 +115,4 @@ OPAL_CALL(opal_xscom_read,			OPAL_XSCOM_READ);
 OPAL_CALL(opal_xscom_write,                     OPAL_XSCOM_WRITE);
 OPAL_CALL(opal_lpc_read,                        OPAL_LPC_READ);
 OPAL_CALL(opal_lpc_write,                       OPAL_LPC_WRITE);
+OPAL_CALL(opal_return_cpu,                      OPAL_RETURN_CPU);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 4ddb339700b9..e239dcfa224c 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -31,6 +31,7 @@
 #include <asm/xics.h>
 #include <asm/rtas.h>
 #include <asm/opal.h>
+#include <asm/kexec.h>
 
 #include "powernv.h"
 
@@ -153,6 +154,16 @@ static void pnv_shutdown(void)
 static void pnv_kexec_cpu_down(int crash_shutdown, int secondary)
 {
         xics_kexec_teardown_cpu(secondary);
+
+        /* Return secondary CPUs to firmware on OPAL v3 */
+        if (firmware_has_feature(FW_FEATURE_OPALv3) && secondary) {
+                mb();
+                get_paca()->kexec_state = KEXEC_STATE_REAL_MODE;
+                mb();
+
+                /* Return the CPU to OPAL */
+                opal_return_cpu();
+        }
 }
 #endif /* CONFIG_KEXEC */