watchdog: aspeed: Sanitize control register values

While some of the critical fields remain the same, there is variation in
the definition of the control register across the SoC generations.
Reserved regions are adjusted, while in other cases the mutability or
behaviour of fields change.

Introduce a callback to sanitize the value on writes to ensure model
behaviour reflects the hardware.

Fixes: 854123b ("wdt: Add Aspeed watchdog device model")
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20210709053107.1829304-2-andrew@aj.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

hw/watchdog/wdt_aspeed.c

@@ -118,13 +118,27 @@ static void aspeed_wdt_reload_1mhz(AspeedWDTState *s)
     }
 }
 
+static uint64_t aspeed_2400_sanitize_ctrl(uint64_t data)
+{
+    return data & 0xffff;
+}
+
+static uint64_t aspeed_2500_sanitize_ctrl(uint64_t data)
+{
+    return (data & ~(0xfUL << 8)) | WDT_CTRL_1MHZ_CLK;
+}
+
+static uint64_t aspeed_2600_sanitize_ctrl(uint64_t data)
+{
+    return data & ~(0x7UL << 7);
+}
 
 static void aspeed_wdt_write(void *opaque, hwaddr offset, uint64_t data,
                              unsigned size)
 {
     AspeedWDTState *s = ASPEED_WDT(opaque);
     AspeedWDTClass *awc = ASPEED_WDT_GET_CLASS(s);
-    bool enable = data & WDT_CTRL_ENABLE;
+    bool enable;
 
     offset >>= 2;
 
@@ -144,6 +158,8 @@ static void aspeed_wdt_write(void *opaque, hwaddr offset, uint64_t data,
         }
         break;
     case WDT_CTRL:
+        data = awc->sanitize_ctrl(data);
+        enable = data & WDT_CTRL_ENABLE;
         if (enable && !aspeed_wdt_is_enabled(s)) {
             s->regs[WDT_CTRL] = data;
             awc->wdt_reload(s);
@@ -207,11 +223,12 @@ static const MemoryRegionOps aspeed_wdt_ops = {
 static void aspeed_wdt_reset(DeviceState *dev)
 {
     AspeedWDTState *s = ASPEED_WDT(dev);
+    AspeedWDTClass *awc = ASPEED_WDT_GET_CLASS(s);
 
     s->regs[WDT_STATUS] = 0x3EF1480;
     s->regs[WDT_RELOAD_VALUE] = 0x03EF1480;
     s->regs[WDT_RESTART] = 0;
-    s->regs[WDT_CTRL] = 0;
+    s->regs[WDT_CTRL] = awc->sanitize_ctrl(0);
     s->regs[WDT_RESET_WIDTH] = 0xFF;
 
     timer_del(s->timer);
@@ -293,6 +310,7 @@ static void aspeed_2400_wdt_class_init(ObjectClass *klass, void *data)
     awc->ext_pulse_width_mask = 0xff;
     awc->reset_ctrl_reg = SCU_RESET_CONTROL1;
     awc->wdt_reload = aspeed_wdt_reload;
+    awc->sanitize_ctrl = aspeed_2400_sanitize_ctrl;
 }
 
 static const TypeInfo aspeed_2400_wdt_info = {
@@ -328,6 +346,7 @@ static void aspeed_2500_wdt_class_init(ObjectClass *klass, void *data)
     awc->reset_ctrl_reg = SCU_RESET_CONTROL1;
     awc->reset_pulse = aspeed_2500_wdt_reset_pulse;
     awc->wdt_reload = aspeed_wdt_reload_1mhz;
+    awc->sanitize_ctrl = aspeed_2500_sanitize_ctrl;
 }
 
 static const TypeInfo aspeed_2500_wdt_info = {
@@ -348,6 +367,7 @@ static void aspeed_2600_wdt_class_init(ObjectClass *klass, void *data)
     awc->reset_ctrl_reg = AST2600_SCU_RESET_CONTROL1;
     awc->reset_pulse = aspeed_2500_wdt_reset_pulse;
     awc->wdt_reload = aspeed_wdt_reload_1mhz;
+    awc->sanitize_ctrl = aspeed_2600_sanitize_ctrl;
 }
 
 static const TypeInfo aspeed_2600_wdt_info = {

include/hw/watchdog/wdt_aspeed.h

@@ -44,6 +44,7 @@ struct AspeedWDTClass {
     uint32_t reset_ctrl_reg;
     void (*reset_pulse)(AspeedWDTState *s, uint32_t property);
     void (*wdt_reload)(AspeedWDTState *s);
+    uint64_t (*sanitize_ctrl)(uint64_t data);
 };
 
 #endif /* WDT_ASPEED_H */