[Qemu-devel] [PATCH v2] hw/arm/aspeed: Unlock SCU when running kernel

[Joel Stanley <joel@jms.id.au>]

The ASPEED hardware contains a lock register for the SCU that disables
any writes to the SCU when it is locked. The machine comes up with the
lock enabled, but on all known hardware u-boot will unlock it and leave
it unlocked when loading the kernel.

This means the kernel expects the SCU to be unlocked. When booting from
an emulated ROM the normal u-boot unlock path is executed. Things don't
go well when booting using the -kernel command line, as u-boot does not
run first.

Change behaviour so that when a kernel is passed to the machine, set the
reset value of the SCU to be unlocked.

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2:
 - use the correct value for the key
 - rename it ASPEED_SCU_PROT_KEY
---
 hw/arm/aspeed.c              | 10 ++++++++++
 hw/arm/aspeed_soc.c          |  2 ++
 hw/misc/aspeed_scu.c         |  5 +++--
 include/hw/misc/aspeed_scu.h |  3 +++
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index ab895ad490af..754df8403273 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -36,6 +36,7 @@ typedef struct AspeedBoardState {
 typedef struct AspeedBoardConfig {
     const char *soc_name;
     uint32_t hw_strap1;
+    uint32_t hw_prot_key;
     const char *fmc_model;
     const char *spi_model;
     uint32_t num_cs;
@@ -186,6 +187,15 @@ static void aspeed_board_init(MachineState *machine,
                             &error_abort);
     object_property_set_int(OBJECT(&bmc->soc), cfg->num_cs, "num-cs",
                             &error_abort);
+    if (machine->kernel_filename) {
+        /*
+         * When booting with a -kernel command line there is no u-boot
+         * that runs to unlock the SCU. In this case set the default to
+         * be unlocked as the kernel expects
+         */
+        object_property_set_int(OBJECT(&bmc->soc), ASPEED_SCU_PROT_KEY,
+                                "hw-prot-key", &error_abort);
+    }
     object_property_set_bool(OBJECT(&bmc->soc), true, "realized",
                              &error_abort);
 
diff --git a/hw/arm/aspeed_soc.c b/hw/arm/aspeed_soc.c
index 5aa3d2ddd9cd..c83b7e207b86 100644
--- a/hw/arm/aspeed_soc.c
+++ b/hw/arm/aspeed_soc.c
@@ -154,6 +154,8 @@ static void aspeed_soc_init(Object *obj)
                               "hw-strap1", &error_abort);
     object_property_add_alias(obj, "hw-strap2", OBJECT(&s->scu),
                               "hw-strap2", &error_abort);
+    object_property_add_alias(obj, "hw-prot-key", OBJECT(&s->scu),
+                              "hw-prot-key", &error_abort);
 
     object_initialize(&s->fmc, sizeof(s->fmc), sc->info->fmc_typename);
     object_property_add_child(obj, "fmc", OBJECT(&s->fmc), NULL);
diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c
index 95022d3607ad..74537ce9755d 100644
--- a/hw/misc/aspeed_scu.c
+++ b/hw/misc/aspeed_scu.c
@@ -85,7 +85,6 @@
 #define BMC_REV              TO_REG(0x19C)
 #define BMC_DEV_ID           TO_REG(0x1A4)
 
-#define PROT_KEY_UNLOCK 0x1688A8A8
 #define SCU_IO_REGION_SIZE 0x1000
 
 static const uint32_t ast2400_a0_resets[ASPEED_SCU_NR_REGS] = {
@@ -192,7 +191,7 @@ static void aspeed_scu_write(void *opaque, hwaddr offset, uint64_t data,
     }
 
     if (reg > PROT_KEY && reg < CPU2_BASE_SEG1 &&
-            s->regs[PROT_KEY] != PROT_KEY_UNLOCK) {
+            s->regs[PROT_KEY] != ASPEED_SCU_PROT_KEY) {
         qemu_log_mask(LOG_GUEST_ERROR, "%s: SCU is locked!\n", __func__);
         return;
     }
@@ -246,6 +245,7 @@ static void aspeed_scu_reset(DeviceState *dev)
     s->regs[SILICON_REV] = s->silicon_rev;
     s->regs[HW_STRAP1] = s->hw_strap1;
     s->regs[HW_STRAP2] = s->hw_strap2;
+    s->regs[PROT_KEY] = s->hw_prot_key;
 }
 
 static uint32_t aspeed_silicon_revs[] = {
@@ -299,6 +299,7 @@ static Property aspeed_scu_properties[] = {
     DEFINE_PROP_UINT32("silicon-rev", AspeedSCUState, silicon_rev, 0),
     DEFINE_PROP_UINT32("hw-strap1", AspeedSCUState, hw_strap1, 0),
     DEFINE_PROP_UINT32("hw-strap2", AspeedSCUState, hw_strap2, 0),
+    DEFINE_PROP_UINT32("hw-prot-key", AspeedSCUState, hw_prot_key, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/misc/aspeed_scu.h b/include/hw/misc/aspeed_scu.h
index bd4ac013f997..d70cc0aeca61 100644
--- a/include/hw/misc/aspeed_scu.h
+++ b/include/hw/misc/aspeed_scu.h
@@ -29,6 +29,7 @@ typedef struct AspeedSCUState {
     uint32_t silicon_rev;
     uint32_t hw_strap1;
     uint32_t hw_strap2;
+    uint32_t hw_prot_key;
 } AspeedSCUState;
 
 #define AST2400_A0_SILICON_REV   0x02000303U
@@ -38,6 +39,8 @@ typedef struct AspeedSCUState {
 
 extern bool is_supported_silicon_rev(uint32_t silicon_rev);
 
+#define ASPEED_SCU_PROT_KEY      0x1688A8A8
+
 /*
  * Extracted from Aspeed SDK v00.03.21. Fixes and extra definitions
  * were added.
-- 
2.14.1