Commit 587164cd, introduced new opal message type (OPAL_MSG_PRD2) and added
opal notifier. But I missed to unregister the notifier during module unload
path. This results in below call trace if you try to unload and load
opal_prd module.
Also add new notifier_block for OPAL_MSG_PRD2 message.

Sample calltrace (modprobe -r opal_prd; modprobe opal_prd)
  [  213.335261] BUG: Unable to handle kernel data access on read at 
0xc0080000192200e0
  [  213.335287] Faulting instruction address: 0xc00000000018d1cc
  [  213.335301] Oops: Kernel access of bad area, sig: 11 [#1]
  [  213.335313] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
  [  213.335736] CPU: 66 PID: 7446 Comm: modprobe Kdump: loaded Tainted: G      
      E     5.14.0prd #759
  [  213.335772] NIP:  c00000000018d1cc LR: c00000000018d2a8 CTR: 
c0000000000cde10
  [  213.335805] REGS: c0000003c4c0f0a0 TRAP: 0300   Tainted: G            E    
  (5.14.0prd)
  [  213.335848] MSR:  9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 
24224824  XER: 20040000
  [  213.335893] CFAR: c00000000018d2a4 DAR: c0080000192200e0 DSISR: 40000000 
IRQMASK: 1
  [  213.335893] GPR00: c00000000018d2a8 c0000003c4c0f340 c000000001995300 
c000000001a5ad08
  [  213.335893] GPR04: c00800000e3700d0 c0000003c4c0f434 c0000000010a8c08 
6e616d6500000000
  [  213.335893] GPR08: 0000000000000000 c0080000192200d0 0000000000000001 
c00800000e351020
  [  213.335893] GPR12: c0000000000cde10 c000000ffffecb80 c0000003c4c0fd00 
0000000000000000
  [  213.335893] GPR16: 0000000000000990 c00800000d950000 c00800000d950990 
c00000000103fd10
  [  213.335893] GPR20: c0000003c4c0fbc0 0000000000000001 c0000003c4c0fbc0 
c00800000e370498
  [  213.335893] GPR24: 0000000000000000 c000000000dab5c8 c000000001a5ad18 
c000000001a5ac80
  [  213.335893] GPR28: 0000000000000008 0000000000000001 c000000001a5ad00 
c000000001a5ad00
  [  213.336170] NIP [c00000000018d1cc] notifier_chain_register+0x2c/0xc0
  [  213.336205] LR [c00000000018d2a8] atomic_notifier_chain_register+0x48/0x80
  [  213.336238] Call Trace:
  [  213.336255] [c0000003c4c0f340] [c000000002090610] 0xc000000002090610 
(unreliable)
  [  213.336281] [c0000003c4c0f3a0] [c00000000018d2b8] 
atomic_notifier_chain_register+0x58/0x80
  [  213.336309] [c0000003c4c0f3f0] [c0000000000cde8c] 
opal_message_notifier_register+0x7c/0x1e0
  [  213.336345] [c0000003c4c0f4b0] [c00800000e3508ac] 
opal_prd_probe+0x84/0x150 [opal_prd]
  [  213.336382] [c0000003c4c0f530] [c00000000097acc8] platform_probe+0x78/0x130
  [  213.336416] [c0000003c4c0f5b0] [c000000000976520] really_probe+0x110/0x5d0
  [  213.336467] [c0000003c4c0f630] [c000000000976b5c] 
__driver_probe_device+0x17c/0x230
  [  213.336512] [c0000003c4c0f6b0] [c000000000976c70] 
driver_probe_device+0x60/0x130
  [  213.336556] [c0000003c4c0f700] [c00000000097746c] 
__driver_attach+0xfc/0x220
  [  213.336592] [c0000003c4c0f780] [c000000000972e68] 
bus_for_each_dev+0xa8/0x130
  [  213.336627] [c0000003c4c0f7e0] [c000000000975b04] driver_attach+0x34/0x50
  [  213.336661] [c0000003c4c0f800] [c000000000974e20] 
bus_add_driver+0x1b0/0x300
  [  213.336696] [c0000003c4c0f890] [c000000000978468] 
driver_register+0x98/0x1a0
  [  213.336732] [c0000003c4c0f900] [c00000000097a878] 
__platform_driver_register+0x38/0x50
  [  213.336768] [c0000003c4c0f920] [c00800000e350dc0] 
opal_prd_driver_init+0x34/0x50 [opal_prd]
  [  213.336804] [c0000003c4c0f940] [c000000000012410] 
do_one_initcall+0x60/0x2d0
  [  213.336821] [c0000003c4c0fa10] [c000000000262c8c] do_init_module+0x7c/0x320
  [  213.336845] [c0000003c4c0fa90] [c000000000266544] load_module+0x3394/0x3650
  [  213.336880] [c0000003c4c0fc90] [c000000000266b34] 
__do_sys_finit_module+0xd4/0x160
  [  213.336914] [c0000003c4c0fdb0] [c000000000031e00] 
system_call_exception+0x140/0x290
  [  213.336958] [c0000003c4c0fe10] [c00000000000c764] 
system_call_common+0xf4/0x258

Fixes: 587164cd ("powerpc/powernv: Add new opal message type")
Signed-off-by: Vasant Hegde <hegdevas...@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/powernv/opal-prd.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/opal-prd.c 
b/arch/powerpc/platforms/powernv/opal-prd.c
index a191f4c60ce7..113bdb151f68 100644
--- a/arch/powerpc/platforms/powernv/opal-prd.c
+++ b/arch/powerpc/platforms/powernv/opal-prd.c
@@ -369,6 +369,12 @@ static struct notifier_block opal_prd_event_nb = {
        .priority       = 0,
 };
 
+static struct notifier_block opal_prd_event_nb2 = {
+       .notifier_call  = opal_prd_msg_notifier,
+       .next           = NULL,
+       .priority       = 0,
+};
+
 static int opal_prd_probe(struct platform_device *pdev)
 {
        int rc;
@@ -390,9 +396,10 @@ static int opal_prd_probe(struct platform_device *pdev)
                return rc;
        }
 
-       rc = opal_message_notifier_register(OPAL_MSG_PRD2, &opal_prd_event_nb);
+       rc = opal_message_notifier_register(OPAL_MSG_PRD2, &opal_prd_event_nb2);
        if (rc) {
                pr_err("Couldn't register PRD2 event notifier\n");
+               opal_message_notifier_unregister(OPAL_MSG_PRD, 
&opal_prd_event_nb);
                return rc;
        }
 
@@ -401,6 +408,8 @@ static int opal_prd_probe(struct platform_device *pdev)
                pr_err("failed to register miscdev\n");
                opal_message_notifier_unregister(OPAL_MSG_PRD,
                                &opal_prd_event_nb);
+               opal_message_notifier_unregister(OPAL_MSG_PRD2,
+                               &opal_prd_event_nb2);
                return rc;
        }
 
@@ -411,6 +420,7 @@ static int opal_prd_remove(struct platform_device *pdev)
 {
        misc_deregister(&opal_prd_dev);
        opal_message_notifier_unregister(OPAL_MSG_PRD, &opal_prd_event_nb);
+       opal_message_notifier_unregister(OPAL_MSG_PRD2, &opal_prd_event_nb2);
        return 0;
 }
 
-- 
2.31.1

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