From: Igor Mammedov <imammedo@redhat.com>

[2] initialized 'No Reboot' bit to 1 by default. And due to quirk it happened
to work with linux iTCO_wdt driver (which clears it on module load).

However spec [1] states:
"
R/W. This bit is set when the “No Reboot” strap (SPKR pin on
ICH9) is sampled high on PWROK.
"

So it should be set only when  '-global ICH9-LPC.noreboot=true' and cleared
when it's false (which should be default).

Fix it to behave according to spec and set 'No Reboot' bit only when
'-global ICH9-LPC.noreboot=true'.

1)
Intel I/O Controller Hub 9 (ICH9) Family Datasheet (rev: 004)
2)

Fixes: 920557971b6 (ich9: add TCO interface emulation)
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250922132600.562193-1-imammedo@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/southbridge/ich9.h | 2 +-
 hw/isa/lpc_ich9.c             | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/hw/southbridge/ich9.h b/include/hw/southbridge/ich9.h
index 1e231e89c9..2c35dd0484 100644
--- a/include/hw/southbridge/ich9.h
+++ b/include/hw/southbridge/ich9.h
@@ -95,7 +95,7 @@ struct ICH9LPCState {
 #define ICH9_CC_OIC                             0x31FF
 #define ICH9_CC_OIC_AEN                         0x1
 #define ICH9_CC_GCS                             0x3410
-#define ICH9_CC_GCS_DEFAULT                     0x00000020
+#define ICH9_CC_GCS_DEFAULT                     0x00000000
 #define ICH9_CC_GCS_NO_REBOOT                   (1 << 5)
 
 /* D28:F[0-5] */
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index 304dffac32..c9cb8f7779 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -132,6 +132,11 @@ static void ich9_cc_init(ICH9LPCState *lpc)
 static void ich9_cc_reset(ICH9LPCState *lpc)
 {
     uint8_t *c = lpc->chip_config;
+    uint32_t gcs = ICH9_CC_GCS_DEFAULT;
+
+    if (lpc->pin_strap.spkr_hi) {
+        gcs |= ICH9_CC_GCS_NO_REBOOT;
+    }
 
     memset(lpc->chip_config, 0, sizeof(lpc->chip_config));
 
@@ -142,7 +147,7 @@ static void ich9_cc_reset(ICH9LPCState *lpc)
     pci_set_long(c + ICH9_CC_D27IR, ICH9_CC_DIR_DEFAULT);
     pci_set_long(c + ICH9_CC_D26IR, ICH9_CC_DIR_DEFAULT);
     pci_set_long(c + ICH9_CC_D25IR, ICH9_CC_DIR_DEFAULT);
-    pci_set_long(c + ICH9_CC_GCS, ICH9_CC_GCS_DEFAULT);
+    pci_set_long(c + ICH9_CC_GCS, gcs);
 
     ich9_cc_update(lpc);
 }
-- 
MST