drivers: spi: spi_context.h: remove multithreading dependency

Replace semaphores with proper atomic flags when used without
multithreading enabled.

Signed-off-by: Michal Kozikowski <michal.kozikowski@nordicsemi.no>

drivers/spi/Kconfig

@@ -24,6 +24,7 @@ config SPI_SHELL
 
 config SPI_ASYNC
 	bool "Asynchronous call support"
+	depends on MULTITHREADING
 	select POLL
 	help
 	  This option enables the asynchronous API calls.

drivers/spi/Kconfig.nrfx

@@ -5,7 +5,6 @@ menuconfig SPI_NRFX
 	bool "nRF SPI nrfx drivers"
 	default y
 	depends on SOC_FAMILY_NORDIC_NRF
-	depends on MULTITHREADING
 	select GPIO
 	select PINCTRL
 	help

drivers/spi/spi_context.h

@@ -28,12 +28,21 @@ enum spi_ctx_runtime_op_mode {
 
 struct spi_context {
 	const struct spi_config *config;
+#ifdef CONFIG_MULTITHREADING
 	const struct spi_config *owner;
+#endif
 	const struct gpio_dt_spec *cs_gpios;
 	size_t num_cs_gpios;
 
+#ifdef CONFIG_MULTITHREADING
 	struct k_sem lock;
 	struct k_sem sync;
+#else
+	/* An atomic flag that signals completed transfer
+	 * when threads are not enabled.
+	 */
+	atomic_t ready;
+#endif /* CONFIG_MULTITHREADING */
 	int sync_status;
 
 #ifdef CONFIG_SPI_ASYNC
@@ -106,6 +115,7 @@ static inline void spi_context_lock(struct spi_context *ctx,
 				    void *callback_data,
 				    const struct spi_config *spi_cfg)
 {
+#ifdef CONFIG_MULTITHREADING
 	bool already_locked = (spi_cfg->operation & SPI_LOCK_ON) &&
 			      (k_sem_count_get(&ctx->lock) == 0) &&
 			      (ctx->owner == spi_cfg);
@@ -114,6 +124,7 @@ static inline void spi_context_lock(struct spi_context *ctx,
 		k_sem_take(&ctx->lock, K_FOREVER);
 		ctx->owner = spi_cfg;
 	}
+#endif /* CONFIG_MULTITHREADING */
 
 #ifdef CONFIG_SPI_ASYNC
 	ctx->asynchronous = asynchronous;
@@ -131,6 +142,7 @@ static inline void spi_context_lock(struct spi_context *ctx,
  */
 static inline void spi_context_release(struct spi_context *ctx, int status)
 {
+#ifdef CONFIG_MULTITHREADING
 #ifdef CONFIG_SPI_SLAVE
 	if (status >= 0 && (ctx->config->operation & SPI_LOCK_ON)) {
 		return;
@@ -148,6 +160,7 @@ static inline void spi_context_release(struct spi_context *ctx, int status)
 		k_sem_give(&ctx->lock);
 	}
 #endif /* CONFIG_SPI_ASYNC */
+#endif /* CONFIG_MULTITHREADING */
 }
 
 static inline size_t spi_context_total_tx_len(struct spi_context *ctx);
@@ -173,6 +186,7 @@ static inline int spi_context_wait_for_completion(struct spi_context *ctx)
 
 	if (wait) {
 		k_timeout_t timeout;
+		uint32_t timeout_ms;
 
 		/* Do not use any timeout in the slave mode, as in this case
 		 * it is not known when the transfer will actually start and
@@ -180,10 +194,10 @@ static inline int spi_context_wait_for_completion(struct spi_context *ctx)
 		 */
 		if (IS_ENABLED(CONFIG_SPI_SLAVE) && spi_context_is_slave(ctx)) {
 			timeout = K_FOREVER;
+			timeout_ms = UINT32_MAX;
 		} else {
 			uint32_t tx_len = spi_context_total_tx_len(ctx);
 			uint32_t rx_len = spi_context_total_rx_len(ctx);
-			uint32_t timeout_ms;
 
 			timeout_ms = MAX(tx_len, rx_len) * 8 * 1000 /
 				     ctx->config->frequency;
@@ -191,11 +205,38 @@ static inline int spi_context_wait_for_completion(struct spi_context *ctx)
 
 			timeout = K_MSEC(timeout_ms);
 		}
-
+#ifdef CONFIG_MULTITHREADING
 		if (k_sem_take(&ctx->sync, timeout)) {
 			LOG_ERR("Timeout waiting for transfer complete");
 			return -ETIMEDOUT;
 		}
+#else
+		if (timeout_ms == UINT32_MAX) {
+			/* In slave mode, we wait indefinitely, so we can go idle. */
+			unsigned int key = irq_lock();
+
+			while (!atomic_get(&ctx->ready)) {
+				k_cpu_atomic_idle(key);
+				key = irq_lock();
+			}
+
+			ctx->ready = 0;
+			irq_unlock(key);
+		} else {
+			const uint32_t tms = k_uptime_get_32();
+
+			while (!atomic_get(&ctx->ready) && (k_uptime_get_32() - tms < timeout_ms)) {
+				k_busy_wait(1);
+			}
+
+			if (!ctx->ready) {
+				LOG_ERR("Timeout waiting for transfer complete");
+				return -ETIMEDOUT;
+			}
+
+			ctx->ready = 0;
+		}
+#endif /* CONFIG_MULTITHREADING */
 		status = ctx->sync_status;
 	}
 
@@ -239,10 +280,15 @@ static inline void spi_context_complete(struct spi_context *ctx,
 			ctx->owner = NULL;
 			k_sem_give(&ctx->lock);
 		}
+
 	}
 #else
 	ctx->sync_status = status;
+#ifdef CONFIG_MULTITHREADING
 	k_sem_give(&ctx->sync);
+#else
+	atomic_set(&ctx->ready, 1);
+#endif /* CONFIG_MULTITHREADING */
 #endif /* CONFIG_SPI_ASYNC */
 }
 
@@ -355,10 +401,12 @@ static inline void spi_context_unlock_unconditionally(struct spi_context *ctx)
 	/* Forcing CS to go to inactive status */
 	_spi_context_cs_control(ctx, false, true);
 
+#ifdef CONFIG_MULTITHREADING
 	if (!k_sem_count_get(&ctx->lock)) {
 		ctx->owner = NULL;
 		k_sem_give(&ctx->lock);
 	}
+#endif /* CONFIG_MULTITHREADING */
 }
 
 /*

drivers/spi/spi_nrfx_spi.c

@@ -278,7 +278,11 @@ static int transceive(const struct device *dev,
 			finish_transaction(dev, -ETIMEDOUT);
 
 			/* Clean up the driver state. */
+#ifdef CONFIG_MULTITHREADING
 			k_sem_reset(&dev_data->ctx.sync);
+#else
+			dev_data->ctx.ready = 0;
+#endif /* CONFIG_MULTITHREADING */
 		}
 
 		spi_context_cs_control(&dev_data->ctx, false);
@@ -432,8 +436,10 @@ static int spi_nrfx_init(const struct device *dev)
 			    nrfx_isr, nrfx_spi_##idx##_irq_handler, 0);	       \
 	}								       \
 	static struct spi_nrfx_data spi_##idx##_data = {		       \
-		SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),		       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
-		SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),		       \
+			(SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),))       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
+			(SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),))       \
 		SPI_CONTEXT_CS_GPIOS_INITIALIZE(SPI(idx), ctx)		       \
 		.dev  = DEVICE_DT_GET(SPI(idx)),			       \
 		.busy = false,						       \

drivers/spi/spi_nrfx_spim.c

@@ -598,7 +598,11 @@ static int transceive(const struct device *dev,
 			finish_transaction(dev, -ETIMEDOUT);
 
 			/* Clean up the driver state. */
+#ifdef CONFIG_MULTITHREADING
 			k_sem_reset(&dev_data->ctx.sync);
+#else
+			dev_data->ctx.ready = 0;
+#endif /* CONFIG_MULTITHREADING */
 #ifdef CONFIG_SOC_NRF52832_ALLOW_SPIM_DESPITE_PAN_58
 			anomaly_58_workaround_clear(dev_data);
 #endif
@@ -817,8 +821,10 @@ static int spi_nrfx_init(const struct device *dev)
 			[CONFIG_SPI_NRFX_RAM_BUFFER_SIZE]		       \
 			SPIM_MEMORY_SECTION(idx);))			       \
 	static struct spi_nrfx_data spi_##idx##_data = {		       \
-		SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),		       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
-		SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),		       \
+			(SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),))       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
+			(SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),))       \
 		SPI_CONTEXT_CS_GPIOS_INITIALIZE(SPIM(idx), ctx)		       \
 		IF_ENABLED(SPI_BUFFER_IN_RAM,				       \
 			(.tx_buffer = spim_##idx##_tx_buffer,		       \

drivers/spi/spi_nrfx_spis.c

@@ -39,7 +39,11 @@ BUILD_ASSERT(!IS_ENABLED(CONFIG_PM_DEVICE_SYSTEM_MANAGED));
 struct spi_nrfx_data {
 	struct spi_context ctx;
 	const struct device *dev;
+#ifdef CONFIG_MULTITHREADING
 	struct k_sem wake_sem;
+#else
+	atomic_t woken_up;
+#endif
 	struct gpio_callback wake_cb_data;
 };
 
@@ -193,7 +197,11 @@ static void wake_callback(const struct device *dev, struct gpio_callback *cb,
 
 	(void)gpio_pin_interrupt_configure_dt(&dev_config->wake_gpio,
 					      GPIO_INT_DISABLE);
+#ifdef CONFIG_MULTITHREADING
 	k_sem_give(&dev_data->wake_sem);
+#else
+	atomic_set(&dev_data->woken_up, 1);
+#endif /* CONFIG_MULTITHREADING */
 }
 
 static void wait_for_wake(struct spi_nrfx_data *dev_data,
@@ -206,7 +214,19 @@ static void wait_for_wake(struct spi_nrfx_data *dev_data,
 			     dev_config->wake_gpio.pin) == 0) {
 		(void)gpio_pin_interrupt_configure_dt(&dev_config->wake_gpio,
 						      GPIO_INT_LEVEL_HIGH);
+#ifdef CONFIG_MULTITHREADING
 		(void)k_sem_take(&dev_data->wake_sem, K_FOREVER);
+#else
+		unsigned int key = irq_lock();
+
+		while (!atomic_get(&dev_data->woken_up)) {
+			k_cpu_atomic_idle(key);
+			key = irq_lock();
+		}
+
+		dev_data->woken_up = 0;
+		irq_unlock(key);
+#endif /* CONFIG_MULTITHREADING */
 	}
 }
 
@@ -482,11 +502,14 @@ static int spi_nrfx_init(const struct device *dev)
 			    nrfx_isr, nrfx_spis_##idx##_irq_handler, 0);       \
 	}								       \
 	static struct spi_nrfx_data spi_##idx##_data = {		       \
-		SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),		       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
-		SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),		       \
+			(SPI_CONTEXT_INIT_LOCK(spi_##idx##_data, ctx),))       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
+			(SPI_CONTEXT_INIT_SYNC(spi_##idx##_data, ctx),))       \
 		.dev  = DEVICE_DT_GET(SPIS(idx)),			       \
-		.wake_sem = Z_SEM_INITIALIZER(				       \
+		IF_ENABLED(CONFIG_MULTITHREADING,			       \
-			spi_##idx##_data.wake_sem, 0, 1),		       \
+			(.wake_sem = Z_SEM_INITIALIZER(			       \
+				spi_##idx##_data.wake_sem, 0, 1),))	       \
 	};								       \
 	PINCTRL_DT_DEFINE(SPIS(idx));					       \
 	static const struct spi_nrfx_config spi_##idx##z_config = {	       \