[PATCH v2 04/25] hw/sensor: tmp105: enforce the configurable fault queue

The fault-queue depth selected in the configuration register was decoded
but never consulted, so the ALERT pin tripped on the very first
out-of-limit conversion regardless of the programmed depth.

Track the consecutive-fault count and only change the ALERT state once
it reaches the programmed depth; any in-range conversion clears the
count. The default configuration keeps the previous behaviour. The count
is migrated through an optional subsection so existing streams stay
compatible.

Signed-off-by: Emmanuel Blot <[email protected]>
---
 hw/sensor/tmp105.c | 87 ++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 55 insertions(+), 32 deletions(-)

diff --git a/hw/sensor/tmp105.c b/hw/sensor/tmp105.c
index f7d0c738ca..5c77f991cc 100644
--- a/hw/sensor/tmp105.c
+++ b/hw/sensor/tmp105.c
@@ -54,6 +54,7 @@ struct TMP105State {
     int16_t temperature;
     int16_t limit[2];
     int faults;
+    uint8_t fault_count;
     uint8_t alarm;
     /*
      * The TMP105 initially looks for a temperature rising above T_high;
@@ -78,43 +79,40 @@ static void tmp105_interrupt_update(TMP105State *s)
 
 static void tmp105_alarm_update(TMP105State *s, bool one_shot)
 {
+    bool fault;
+
     if (FIELD_EX8(s->config, CONFIG, SHUTDOWN_MODE) && !one_shot) {
         return;
     }
 
-    if (FIELD_EX8(s->config, CONFIG, THERMOSTAT_MODE)) {
-        /*
-         * TM == 1 : Interrupt mode. We signal Alert when the
-         * temperature rises above T_high, and expect the guest to clear
-         * it (eg by reading a device register).
-         */
-        if (s->detect_falling) {
-            if (s->temperature < s->limit[0]) {
-                s->alarm = 1;
-                s->detect_falling = false;
-            }
-        } else {
-            if (s->temperature >= s->limit[1]) {
-                s->alarm = 1;
-                s->detect_falling = true;
-            }
-        }
+    /*
+     * A fault is a conversion that lies outside the limit currently being
+     * watched: above T_high while looking for the alarm to trip, below T_low
+     * afterwards.
+     */
+    if (s->detect_falling) {
+        fault = s->temperature < s->limit[0];
     } else {
-        /*
-         * TM == 0 : Comparator mode. We signal Alert when the temperature
-         * rises above T_high, and stop signalling it when the temperature
-         * falls below T_low.
-         */
+        fault = s->temperature >= s->limit[1];
+    }
+
+    if (!fault) {
+        s->fault_count = 0;
+    } else if (++s->fault_count >= s->faults) {
+        s->fault_count = 0;
         if (s->detect_falling) {
-            if (s->temperature < s->limit[0]) {
-                s->alarm = 0;
-                s->detect_falling = false;
-            }
+            /*
+             * Temperature fell back below T_low. In comparator mode (TM == 0)
+             * the alarm is released; in interrupt mode (TM == 1) it is
+             * asserted again and the guest is expected to clear it by reading
+             * a register.
+             */
+            s->alarm = FIELD_EX8(s->config, CONFIG, THERMOSTAT_MODE);
+            s->detect_falling = false;
         } else {
-            if (s->temperature >= s->limit[1]) {
-                s->alarm = 1;
-                s->detect_falling = true;
-            }
+            /* Temperature rose to or above T_high: assert the alarm. */
+            s->alarm = 1;
+            s->detect_falling = true;
         }
     }
 
@@ -204,7 +202,12 @@ static void tmp105_write(TMP105State *s)
         }
         s->config = FIELD_DP8(s->buf[0], CONFIG, ONE_SHOT, 0);
         s->faults = tmp105_faultq[FIELD_EX8(s->config, CONFIG, FAULT_QUEUE)];
-        tmp105_alarm_update(s, FIELD_EX8(s->buf[0], CONFIG, ONE_SHOT));
+        if (FIELD_EX8(s->buf[0], CONFIG, ONE_SHOT) &&
+            FIELD_EX8(s->config, CONFIG, SHUTDOWN_MODE)) {
+            tmp105_alarm_update(s, true);
+        } else {
+            tmp105_interrupt_update(s);
+        }
         break;
 
     case TMP105_REG_T_LOW:
@@ -213,7 +216,7 @@ static void tmp105_write(TMP105State *s)
             s->limit[s->pointer & 1] = (int16_t)
                     ((((uint16_t) s->buf[0]) << 8) | (s->buf[1] & 0xf0));
         }
-        tmp105_alarm_update(s, false);
+        tmp105_interrupt_update(s);
         break;
     }
 }
@@ -281,6 +284,13 @@ static bool detect_falling_needed(void *opaque)
     return s->detect_falling;
 }
 
+static bool fault_count_needed(void *opaque)
+{
+    const TMP105State *s = opaque;
+
+    return s->fault_count != 0;
+}
+
 static const VMStateDescription vmstate_tmp105_detect_falling = {
     .name = "TMP105/detect-falling",
     .version_id = 1,
@@ -292,6 +302,17 @@ static const VMStateDescription vmstate_tmp105_detect_falling = {
     }
 };
 
+static const VMStateDescription vmstate_tmp105_fault_count = {
+    .name = "TMP105/fault-count",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = fault_count_needed,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT8(fault_count, TMP105State),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_tmp105 = {
     .name = "TMP105",
     .version_id = 0,
@@ -310,6 +331,7 @@ static const VMStateDescription vmstate_tmp105 = {
     },
     .subsections = (const VMStateDescription * const []) {
         &vmstate_tmp105_detect_falling,
+        &vmstate_tmp105_fault_count,
         NULL
     }
 };
@@ -322,6 +344,7 @@ static void tmp105_reset_hold(Object *obj, ResetType type)
     s->pointer = 0;
     s->config = 0;
     s->faults = tmp105_faultq[FIELD_EX8(s->config, CONFIG, FAULT_QUEUE)];
+    s->fault_count = 0;
     s->alarm = 0;
     s->detect_falling = false;
 

-- 
2.50.1