device: store device pm busy status in the state structure

Move the busy status from a global atomic bit sequence to atomic flags
in the device PM state.  While this temporarily adds 4 bytes to each
PM structure the whole device PM infrastructure will be refactored and
it's likely the extra memory can be recovered.

Signed-off-by: Peter Bigot <[email protected]>

include/device.h

@@ -270,8 +270,11 @@ struct device_pm {
 	const struct device *dev;
 	/** Lock to synchronize the get/put operations */
 	struct k_sem lock;
+	/* Following are packed fields protected by #lock. */
 	/** Device pm enable flag */
-	bool enable;
+	bool enable : 1;
+	/* Following are packed fields accessed with atomic bit operations. */
+	atomic_t atomic_flags;
 	/** Device usage count */
 	atomic_t usage;
 	/** Device idle internal power state */
@@ -284,6 +287,11 @@ struct device_pm {
 	struct k_poll_signal signal;
 };
 
+/** Bit position in device_pm::atomic_flags that records whether the
+ * device is busy.
+ */
+#define DEVICE_PM_ATOMIC_FLAGS_BUSY_BIT 0
+
 /**
  * @brief Runtime device dynamic structure (in RAM) per driver instance
  *

include/linker/common-ram.ld

@@ -13,27 +13,6 @@
 	} GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
 #endif
 
-/*
- * Space for storing per device init status and busy bitmap in case PM is
- * enabled. Since we do not know beforehand the number of devices,
- * we go through the below mechanism to allocate the required space.
- * Both are made of 1 bit per-device instance, so we compute the size of
- * of an entire bitfield, aligned on 32bits.
- */
-#define DEVICE_COUNT \
-	((__device_end - __device_start) / _DEVICE_STRUCT_SIZEOF)
-#define DEVICE_BITFIELD_SIZE	(((DEVICE_COUNT + 31) / 32) * 4)
-
-#ifdef CONFIG_PM_DEVICE
-#define DEVICE_BUSY_BITFIELD()			\
-		FILL(0x00);			\
-		__device_busy_start = .;	\
-		. = . + DEVICE_BITFIELD_SIZE;	\
-		__device_busy_end = .;
-#else
-#define DEVICE_BUSY_BITFIELD()
-#endif
-
 	SECTION_DATA_PROLOGUE(devices,,)
 	{
 		/* link in devices objects, which are tied to the init ones;
@@ -47,7 +26,6 @@
 		CREATE_OBJ_LEVEL(device, APPLICATION)
 		CREATE_OBJ_LEVEL(device, SMP)
 		__device_end = .;
-		DEVICE_BUSY_BITFIELD()
 	} GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
 
 	SECTION_DATA_PROLOGUE(initshell,,)

kernel/device.c

@@ -25,12 +25,6 @@ extern const struct device __device_end[];
 
 extern uint32_t __device_init_status_start[];
 
-#ifdef CONFIG_PM_DEVICE
-extern uint32_t __device_busy_start[];
-extern uint32_t __device_busy_end[];
-#define DEVICE_BUSY_SIZE (__device_busy_end - __device_busy_start)
-#endif
-
 static inline void device_pm_state_init(const struct device *dev)
 {
 #ifdef CONFIG_PM_DEVICE
@@ -180,43 +174,46 @@ int device_pm_control_nop(const struct device *unused_device,
 
 int device_any_busy_check(void)
 {
-	int i = 0;
+	const struct device *dev = __device_start;
 
-	for (i = 0; i < DEVICE_BUSY_SIZE; i++) {
-		if (__device_busy_start[i] != 0U) {
+	while (dev < __device_end) {
+		if (atomic_test_bit(&dev->pm->atomic_flags,
+				    DEVICE_PM_ATOMIC_FLAGS_BUSY_BIT)) {
 			return -EBUSY;
 		}
+		++dev;
 	}
+
 	return 0;
 }
 
-int device_busy_check(const struct device *chk_dev)
+int device_busy_check(const struct device *dev)
 {
-	if (atomic_test_bit((const atomic_t *)__device_busy_start,
-			    (chk_dev - __device_start))) {
+	if (atomic_test_bit(&dev->pm->atomic_flags,
+			    DEVICE_PM_ATOMIC_FLAGS_BUSY_BIT)) {
 		return -EBUSY;
 	}
 	return 0;
 }
 
 #endif
 
-void device_busy_set(const struct device *busy_dev)
+void device_busy_set(const struct device *dev)
 {
 #ifdef CONFIG_PM_DEVICE
-	atomic_set_bit((atomic_t *) __device_busy_start,
-		       (busy_dev - __device_start));
+	atomic_set_bit(&dev->pm->atomic_flags,
+		       DEVICE_PM_ATOMIC_FLAGS_BUSY_BIT);
 #else
-	ARG_UNUSED(busy_dev);
+	ARG_UNUSED(dev);
 #endif
 }
 
-void device_busy_clear(const struct device *busy_dev)
+void device_busy_clear(const struct device *dev)
 {
 #ifdef CONFIG_PM_DEVICE
-	atomic_clear_bit((atomic_t *) __device_busy_start,
-			 (busy_dev - __device_start));
+	atomic_clear_bit(&dev->pm->atomic_flags,
+			 DEVICE_PM_ATOMIC_FLAGS_BUSY_BIT);
 #else
-	ARG_UNUSED(busy_dev);
+	ARG_UNUSED(dev);
 #endif
 }