add support for spin locks

3 files changed, 45 insertions, 36 deletions

diff --git a/arch/arm/mach-mvf/mvf_sema4.c b/arch/arm/mach-mvf/mvf_sema4.c
index aa354c33de4d..31e40f6d02f0 100644
--- a/arch/arm/mach-mvf/mvf_sema4.c
+++ b/arch/arm/mach-mvf/mvf_sema4.c
@@ -71,12 +71,12 @@ static irqreturn_t sema4_irq_handler(int irq, void *dev_id)
 			// make sure there's a gate assigned
 			if(gates[gate_num])
 			{
-				if(gates[gate_num]->use_interrupts) {
+				//if(gates[gate_num]->use_interrupts) {
 					// wake up whoever was aiting
 					wake_up_interruptible(&(gates[gate_num]->wait_queue));
 					// bump stats
 					gates[gate_num]->interrupts++;
-				}
+				//}
 			}
 		}
 	}
@@ -111,7 +111,7 @@ static int initialize(void)
 	return 0;
 }
 
-int mvf_sema4_assign(int gate_num, bool use_interrupts, MVF_SEMA4** sema4_p)
+int mvf_sema4_assign(int gate_num, MVF_SEMA4** sema4_p)
 {
 	int retval;
 	u32 cp0ine;
@@ -140,17 +140,13 @@ int mvf_sema4_assign(int gate_num, bool use_interrupts, MVF_SEMA4** sema4_p)
 
 	gates[gate_num] = *sema4_p;
 	(*sema4_p)->gate_num = gate_num;
-	(*sema4_p)->use_interrupts = use_interrupts;
 
-	if(use_interrupts)
-	{
-		init_waitqueue_head(&((*sema4_p)->wait_queue));
-		local_irq_save(irq_flags);
-		cp0ine = readl(MVF_IO_ADDRESS(SEMA4_CP0INE));
-		cp0ine |= MASK_FROM_GATE(gate_num);
-		writel(cp0ine, MVF_IO_ADDRESS(SEMA4_CP0INE));
-		local_irq_restore(irq_flags);
-	}
+	init_waitqueue_head(&((*sema4_p)->wait_queue));
+	local_irq_save(irq_flags);
+	cp0ine = readl(MVF_IO_ADDRESS(SEMA4_CP0INE));
+	cp0ine |= MASK_FROM_GATE(gate_num);
+	writel(cp0ine, MVF_IO_ADDRESS(SEMA4_CP0INE));
+	local_irq_restore(irq_flags);
 
 	// debugfs
 	sprintf(debugfs_gatedir_name, "%d", gate_num);
@@ -175,14 +171,11 @@ int mvf_sema4_deassign(MVF_SEMA4 *sema4)
 		return -EINVAL;
 	gate_num = sema4->gate_num;
 
-	if(sema4->use_interrupts)
-	{
-		local_irq_save(irq_flags);
-		cp0ine = readl(MVF_IO_ADDRESS(SEMA4_CP0INE));
-		cp0ine &= ~MASK_FROM_GATE(gate_num);
-		writel(cp0ine, MVF_IO_ADDRESS(SEMA4_CP0INE));
-		local_irq_restore(irq_flags);
-	}
+	local_irq_save(irq_flags);
+	cp0ine = readl(MVF_IO_ADDRESS(SEMA4_CP0INE));
+	cp0ine &= ~MASK_FROM_GATE(gate_num);
+	writel(cp0ine, MVF_IO_ADDRESS(SEMA4_CP0INE));
+	local_irq_restore(irq_flags);
 
 	kfree(sema4);
 	gates[gate_num] = NULL;
@@ -191,21 +184,28 @@ int mvf_sema4_deassign(MVF_SEMA4 *sema4)
 }
 EXPORT_SYMBOL(mvf_sema4_deassign);
 
-static void add_latency_stat(MVF_SEMA4 *sema4) {
+static long delta_time(struct timeval *start) {
 
 	struct timeval now;
-	long latency;
+	long now_us, start_us;
 
 	do_gettimeofday(&now);
 
-	latency = (now.tv_sec * 1000000) + now.tv_usec;
-	latency -= (sema4->request_time.tv_sec * 1000000) + sema4->request_time.tv_usec;
+	now_us = (now.tv_sec * 1000000) + now.tv_usec;
+	start_us = (start->tv_sec * 1000000) + start->tv_usec;
+
+	return now_us > start_us ? now_us - start_us : 0;
+}
+
+static void add_latency_stat(MVF_SEMA4 *sema4) {
+
+	long latency = delta_time(&sema4->request_time);
 
 	sema4->total_latency_us += latency;
 	sema4->worst_latency_us = sema4->worst_latency_us < latency ? latency : sema4->worst_latency_us;
 }
 
-int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us)
+int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us, bool use_interrupts)
 {
 	int retval;
 	int gate_num;
@@ -213,11 +213,6 @@ int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us)
 		return -EINVAL;
 	gate_num = sema4->gate_num;
 
-	// cant use timeouts if not using interruppts
-	// TODO use spin lock if not using interrupts
-	if((!sema4->use_interrupts) && timeout_us)
-		return -EINVAL;
-
 	// bump stats
 	gates[gate_num]->attempts++;
 	do_gettimeofday(&gates[gate_num]->request_time);
@@ -235,6 +230,21 @@ int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us)
 		return -EBUSY;
 	}
 
+	// spin lock?
+	if(!use_interrupts) {
+		while(readb(MVF_IO_ADDRESS(MVF_SEMA4_BASE_ADDR) + gate_num) != LOCK_VALUE) {
+
+			if((timeout_us != 0xffffffff) && (delta_time(&gates[gate_num]->request_time) > timeout_us)) {
+				gates[gate_num]->failures++;
+				return -EBUSY;
+			}
+
+			writeb(LOCK_VALUE, MVF_IO_ADDRESS(MVF_SEMA4_BASE_ADDR) + gate_num);
+		}
+		add_latency_stat(gates[gate_num]);
+		return 0;
+	}
+
 	// wait forever?
 	if(timeout_us == 0xffffffff)
 	{
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index a2e6d2aa16b3..e13e020cab2e 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -439,7 +439,7 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
 	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
 
 #ifdef CONFIG_ARCH_MVF
-	result = mvf_sema4_lock(sema4, 10000000);
+	result = mvf_sema4_lock(sema4, 10000000, true);
 	if(result)
 		return result;
 #endif
@@ -621,7 +621,7 @@ static int __init i2c_imx_probe(struct platform_device *pdev)
 
 #ifdef CONFIG_ARCH_MVF
 	// for makeing sure not in use by MQX concurrently
-	if(mvf_sema4_assign(MVF_I2C_SEMAPHORE_NUMBER, true, &sema4)) {
+	if(mvf_sema4_assign(MVF_I2C_SEMAPHORE_NUMBER, &sema4)) {
 		dev_err(&pdev->dev, "could not assign MQX semaphore %d\n", MVF_I2C_SEMAPHORE_NUMBER);
 		goto fail5;
 	}
diff --git a/include/linux/mvf_sema4.h b/include/linux/mvf_sema4.h
index 7b25996f9417..aa2379a9de05 100644
--- a/include/linux/mvf_sema4.h
+++ b/include/linux/mvf_sema4.h
@@ -11,7 +11,6 @@
 
 typedef struct mvf_sema4_handle_struct {
 	int gate_num;
-	int use_interrupts;
 	wait_queue_head_t wait_queue;
 	// stats
 	u32 attempts;
@@ -22,9 +21,9 @@ typedef struct mvf_sema4_handle_struct {
 	u32 worst_latency_us;
 } MVF_SEMA4;
 
-int mvf_sema4_assign(int gate_num, bool use_interrupts, MVF_SEMA4** sema4_p);
+int mvf_sema4_assign(int gate_num, MVF_SEMA4** sema4_p);
 int mvf_sema4_deassign(MVF_SEMA4 *sema4);
-int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us);
+int mvf_sema4_lock(MVF_SEMA4 *sema4, unsigned int timeout_us, bool use_interrupts);
 int mvf_sema4_unlock(MVF_SEMA4 *sema4);
 
 #endif