Device trying to suspend when screen is turned off by proximity sensor (during a call)

Why isn't it valid for the system CPU to suspend during a phone call? Does android enforce such a restriction?

Yeah, checking android this is actually an expected behavior (the phone will not suspend anyway because of a wakelock).

The question I had initially was actually regarding the proximity sensor, and how would that work when an app decides to use it without any general suspend blocker. Not sure if the hardware will trigger the cpu in order for the device to not be suspended when the proximity sensor is active.

But at least for voicecall, you're right, we can mark this bug as invalid.

Actually in Android the system will try to invoke the early_suspend during a phone call. but it can not go to the deep sleep because of the wakelock. so I suggest that the psensor driver should be added the wakelock to prevent the issue.
Please add and check the follows:

--- a/mediatek/custom/common/kernel/alsps/tmd2772_auto/tmd2772.c
+++ b/mediatek/custom/common/kernel/alsps/tmd2772_auto/tmd2772.c
@@ -64,6 +64,7 @@ static u8 offset_data=0;
 #define PRO_OFFSET 1
 static u16 tmp_data=0;
 #define OFFDATA_DEFAULT 1
+struct wake_lock psensor_lock;
 //end
 /******************************************************************************
  * extern functions
@@ -2417,6 +2418,7 @@ int TMD2772_ps_operate(void* self, uint32_t command, void* buff_in, int size_in,
      tmd2772_ps_calibrate_call(obj->client);
      TMD2772_init_client(obj->client);
      #endif
+ wake_lock(&psensor_lock);
      if((err = TMD2772_enable_ps(obj->client, 1)))
      {
       APS_ERR("enable ps fail: %d\n", err);
@@ -2437,6 +2439,7 @@ int TMD2772_ps_operate(void* self, uint32_t command, void* buff_in, int size_in,
     }
     else
     {
+ wake_unlock(&psensor_lock);
      if((err = TMD2772_enable_ps(obj->client, 0)))
      {
       APS_ERR("disable ps fail: %d\n", err);
@@ -2819,7 +2822,7 @@ static int TMD2772_i2c_probe(struct i2c_client *client, const struct i2c_device_

  mutex_init(&mutex);
  TMD2772_i2c_client = client;
-
+ wake_lock_init(&psensor_lock,WAKE_LOCK_SUSPEND,"psensor wakelock");
  if(1 == obj->hw->polling_mode_ps)
   //if (1)
   {