hw/misc/aspeed_scu: Support the Frequency Counter Control register for AST2700

According to the datasheet:
BIT[1] (SCU_FREQ_OSC_EN) enables the oscillator frequency measurement counter.
BIT[6] (SCU_FREQ_DONE) indicates the measurement is finished.
Firmware polls BIT[6] to determine when measurement is complete.
The flag can be cleared by writing BIT[1] to 0.

To simulate this hardware behavior in QEMU:
If BIT[1] is set to 1, BIT[6] is immediately set to 1 to avoid
firmware hanging during polling.
If BIT[1] is cleared to 0, BIT[6] is also cleared to 0 to match
hardware semantics.

The initial value of this register is initialized to 0x80, reflecting the
default value confirmed from an EVB register dump.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250618080006.846355-3-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c
index 4930e00fed1444ad42f7140c28bd4d1694d153bf..11d07391088260f5d790a868213ea9f42cbcb128 100644 (file)
--- a/hw/misc/aspeed_scu.c
+++ b/hw/misc/aspeed_scu.c
@@ -176,6 +176,7 @@
 #define AST2700_SCUIO_UARTCLK_GEN       TO_REG(0x330)
 #define AST2700_SCUIO_HUARTCLK_GEN      TO_REG(0x334)
 #define AST2700_SCUIO_CLK_DUTY_MEAS_RST TO_REG(0x388)
+#define AST2700_SCUIO_FREQ_CNT_CTL      TO_REG(0x3A0)
 
 #define SCU_IO_REGION_SIZE 0x1000
 
@@ -1022,6 +1023,10 @@ static void aspeed_ast2700_scuio_write(void *opaque, hwaddr offset,
         s->regs[reg - 1] ^= data;
         updated = true;
         break;
+    case AST2700_SCUIO_FREQ_CNT_CTL:
+        s->regs[reg] = deposit32(s->regs[reg], 6, 1, !!(data & BIT(1)));
+        updated = true;
+        break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: Unhandled write at offset 0x%" HWADDR_PRIx "\n",
@@ -1066,6 +1071,7 @@ static const uint32_t ast2700_a0_resets_io[ASPEED_AST2700_SCU_NR_REGS] = {
     [AST2700_SCUIO_UARTCLK_GEN]         = 0x00014506,
     [AST2700_SCUIO_HUARTCLK_GEN]        = 0x000145c0,
     [AST2700_SCUIO_CLK_DUTY_MEAS_RST]   = 0x0c9100d2,
+    [AST2700_SCUIO_FREQ_CNT_CTL]        = 0x00000080,
 };
 
 static void aspeed_2700_scuio_class_init(ObjectClass *klass, const void *data)