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

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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>
This commit is contained in:
Jamin Lin 2025-06-18 16:00:05 +08:00 • committed by Cédric Le Goater
parent 51ac481bff
commit a6ca5dfccc
1 changed files with 6 additions and 0 deletions
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6
hw/misc/aspeed_scu.c
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@ -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)