flash: spi_nor: automatically run device runtime PM

Automatically handle device runtime PM for all flash API calls.
Asynchronously release the device after a small delay to minimise power
state transitions under multiple sequential API calls (e.g. NVS).

Signed-off-by: Jordan Yates <jordan@embeint.com>

doc/releases/migration-guide-4.0.rst

@@ -196,6 +196,11 @@ Other Subsystems
 Flash map
 =========
 
+ * ``CONFIG_SPI_NOR_IDLE_IN_DPD`` has been removed from the :kconfig:option:`CONFIG_SPI_NOR`
+   driver. An enhanced version of this functionality can be obtained by enabling
+   :ref:`pm-device-runtime` on the device (Tunable with
+   :kconfig:option:`CONFIG_SPI_NOR_ACTIVE_DWELL_MS`).
+
 hawkBit
 =======
 

drivers/flash/Kconfig.nor

@@ -78,4 +78,15 @@ config SPI_NOR_FLASH_LAYOUT_PAGE_SIZE
 	  (32768), the sector size (4096), or any non-zero multiple of the
 	  sector size.
 
+config SPI_NOR_ACTIVE_DWELL_MS
+	int "Dwell period (ms) after last use to stay in active mode"
+	depends on PM_DEVICE_RUNTIME
+	default 10
+	help
+	  Flash accesses commonly occur in bursts, where entering and exiting DPD
+	  mode between each access adds significantly to the total operation time.
+	  This option controls how long to remain in active mode after each API
+	  call, eliminating the active->idle->active transition sequence if another
+	  transaction occurs before the dwell period expires.
+
 endif # SPI_NOR

drivers/flash/spi_nor.c

@@ -19,6 +19,7 @@
 #include <zephyr/logging/log.h>
 #include <zephyr/sys_clock.h>
 #include <zephyr/pm/device.h>
+#include <zephyr/pm/device_runtime.h>
 
 #include "spi_nor.h"
 #include "jesd216.h"
@@ -65,6 +66,12 @@ LOG_MODULE_REGISTER(spi_nor, CONFIG_FLASH_LOG_LEVEL);
 #define ANY_INST_HAS_WP_GPIOS ANY_INST_HAS_PROP(wp_gpios)
 #define ANY_INST_HAS_HOLD_GPIOS ANY_INST_HAS_PROP(hold_gpios)
 
+#ifdef CONFIG_SPI_NOR_ACTIVE_DWELL_MS
+#define ACTIVE_DWELL_MS CONFIG_SPI_NOR_ACTIVE_DWELL_MS
+#else
+#define ACTIVE_DWELL_MS 0
+#endif
+
 #define DEV_CFG(_dev_) ((const struct spi_nor_config * const) (_dev_)->config)
 
 /* MXICY Related defines*/
@@ -762,11 +769,19 @@ static int spi_nor_read(const struct device *dev, off_t addr, void *dest,
 		return -EINVAL;
 	}
 
+	/* Ensure flash is powered before read */
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 
 	ret = spi_nor_cmd_addr_read(dev, SPI_NOR_CMD_READ, addr, dest, size);
 
 	release_device(dev);
+
+	/* Release flash power requirement */
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
 	return ret;
 }
 
@@ -779,6 +794,10 @@ static int flash_spi_nor_ex_op(const struct device *dev, uint16_t code,
 	ARG_UNUSED(in);
 	ARG_UNUSED(out);
 
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 
 	switch (code) {
@@ -794,6 +813,7 @@ static int flash_spi_nor_ex_op(const struct device *dev, uint16_t code,
 	}
 
 	release_device(dev);
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
 	return ret;
 }
 #endif
@@ -811,6 +831,11 @@ static int spi_nor_write(const struct device *dev, off_t addr,
 		return -EINVAL;
 	}
 
+	/* Ensure flash is powered before write */
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 	ret = spi_nor_write_protection_set(dev, false);
 	if (ret == 0) {
@@ -858,6 +883,9 @@ static int spi_nor_write(const struct device *dev, off_t addr,
 	}
 
 	release_device(dev);
+
+	/* Release flash power requirement */
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
 	return ret;
 }
 
@@ -881,6 +909,11 @@ static int spi_nor_erase(const struct device *dev, off_t addr, size_t size)
 		return -EINVAL;
 	}
 
+	/* Ensure flash is powered before erase */
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 	ret = spi_nor_write_protection_set(dev, false);
 
@@ -936,6 +969,8 @@ static int spi_nor_erase(const struct device *dev, off_t addr, size_t size)
 
 	release_device(dev);
 
+	/* Release flash power requirement */
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
 	return ret;
 }
 
@@ -977,12 +1012,18 @@ static int spi_nor_write_protection_set(const struct device *dev,
 static int spi_nor_sfdp_read(const struct device *dev, off_t addr,
 			     void *dest, size_t size)
 {
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 
 	int ret = read_sfdp(dev, addr, dest, size);
 
 	release_device(dev);
 
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
+
 	return ret;
 }
 
@@ -995,12 +1036,18 @@ static int spi_nor_read_jedec_id(const struct device *dev,
 		return -EINVAL;
 	}
 
+	if (pm_device_runtime_get(dev) < 0) {
+		return -EIO;
+	}
+
 	acquire_device(dev);
 
 	int ret = spi_nor_cmd_read(dev, SPI_NOR_CMD_RDID, id, SPI_NOR_MAX_ID_LEN);
 
 	release_device(dev);
 
+	(void)pm_device_runtime_put_async(dev, K_MSEC(ACTIVE_DWELL_MS));
+
 	return ret;
 }