Re: [PATCH v1 1/2] hw/misc/aspeed_sbc: Derive ABR state from OTP config straps

["Cédric Le Goater" <clg@kaod.org>]

Hello,

> However, the OTP configuration can also be programmed at runtime.
> Therefore, reading the OTP configuration only once at realize/reset time
> may leave the SBC STATUS register out of sync if the OTP
> configuration is changed afterward.
> 
> I see two possible approaches to keep the SBC STATUS register
> synchronized with the OTP configuration:
> 
> Update the SBC STATUS register at reset and whenever the relevant
> OTP configuration is programmed. This would keep the cached STATUS
> value synchronized with the latest OTP configuration.

Caching values is always a problem. Unless performance is impacted,
computing is better.

> Derive the relevant SBC STATUS bits directly from the OTP
> configuration whenever the STATUS register is read. This avoids
> maintaining a cached copy of the OTP-derived state.

yes something like :

   static uint32_t aspeed_otp_read_cfg0(AspeedSBCState *s)
  {
@@ -110,6 +111,23 @@ static uint64_t aspeed_sbc_read(void *op
      }
  
      switch (addr) {
+    case R_STATUS: {
+        uint32_t val = s->regs[R_STATUS];
+
+        if (aspeed_get_abr_state(s)) {
+            val |= ABR_EN;
+        } else {
+            val &= ~ABR_EN;
+        }

is better IMO. The SBC status register is a reflection of the OTP
fuse state. You could ask he HW designers for info on how the state
is maintained.

Thanks,

C.