reading counter works, measured periods are plausible

driver/counter.c

@@ -6,6 +6,9 @@
 #include <linux/of_device.h>
 #include <linux/gpio/consumer.h>
 #include <linux/spi/spi.h>
+#include <linux/interrupt.h>
+#include <linux/of_irq.h>
+#include <linux/workqueue.h>
 
 #include "ls7366r.h"
 
@@ -107,7 +110,6 @@ static int read32(struct spi_device *client, u8 c, u32 *r) {
     printk("counter - Error! spi_sync_transfer failed in read32\n");
     return ret;
   }
-  printk("counter - Info! rx_buf: %02x %02x %02x %02x %02x\n", rx_buf[0], rx_buf[1], rx_buf[2], rx_buf[3], rx_buf[4]);
   *r = ((u32)rx_buf[1] << 24) | ((u32)rx_buf[2] << 16) | ((u32)rx_buf[3] << 8) | ((u32)rx_buf[4]);
   return 0;
 }
@@ -126,14 +128,11 @@ static int read8(struct spi_device *client, u8 c, u8 *r) {
     printk("counter - Error! spi_sync_transfer failed in read8\n");
     return ret;
   }
-  printk("counter - Info! rx_buf: %02x %02x\n", rx_buf[0], rx_buf[1]);
   *r = rx_buf[1];
   return 0;
 }
 
 
-
-
 static struct of_device_id ls7366r_driver_ids[] = {
   {
     .compatible = "hottis,ls7366r",
@@ -157,6 +156,8 @@ static struct spi_driver ls7366r_driver = {
   },
 };
 
+static struct spi_device *spi_client;
+
 static int dt_ls7366r_probe(struct spi_device *client) {
   printk("counter - ls7366r probing\n");
   
@@ -188,16 +189,12 @@ static int dt_ls7366r_probe(struct spi_device *client) {
     printk("counter - Error! read8 failed in probe\n");
     return ret;
   }
-  printk("counter - Info! x = %02x\n", x);
+  if (x != MDR0_ILO) {
-
+    printk("counter - Error! failed to initialize counter\n");
-  u32 y;
+    return -1;
-  ret = read32(client, CMD_RD | REG_OTR, &y);
-  if (ret < 0) {
-    printk("counter - Error! read32 failed in probe\n");
-    return ret;
   }
-  printk("counter - Info! y = %d\n", y);
 
+  spi_client = client;
 
   return 0;
 }
@@ -207,11 +204,119 @@ static void dt_ls7366r_remove(struct spi_device *client) {
 }
 
 
+/* interrupt stuff */
+static int dt_interrupt_probe(struct platform_device *pdev);
+static void dt_interrupt_remove(struct platform_device *pdev);
+
+static struct of_device_id interrupt_driver_ids[] = {
+  {
+    .compatible = "hottis,intr",
+  }, 
+  {},
+};
+MODULE_DEVICE_TABLE(of, interrupt_driver_ids);
+
+static struct platform_driver interrupt_driver = {
+  .probe = dt_interrupt_probe,
+  .remove = dt_interrupt_remove,
+  .driver = {
+    .name = "interrupt_device_driver",
+    .of_match_table = interrupt_driver_ids,
+  },
+};
+
+static struct gpio_desc *counter_interrupt;
+static int irq_number;
+
+// workqueue
+struct counter_irq_data {
+  struct work_struct work;
+  u64 timestamp;
+  struct spi_device *client;
+  u64 last_timestamp;
+  u32 last_value;
+};
+static struct counter_irq_data counter_irq_wq_data;
+
+static void counter_worker(struct work_struct *work) {
+  struct counter_irq_data *data = container_of(work, struct counter_irq_data, work);
+  u64 ts = data->timestamp;
+
+  u32 counter_value;
+  int ret = read32(data->client, CMD_RD | REG_OTR, &counter_value);
+
+  if (ret < 0) {
+    printk("counter - Error! read32 failed in counter_worker\n");
+    return;
+  }
+
+  if (data->last_value) {
+    u32 period = counter_value - data->last_value;
+    u64 duration = ts - data->last_timestamp;
+    printk("counter - Info! ts = %llu, duration = %llu, period = %u\n", ts, duration, period);
+  }
+  data->last_value = counter_value;
+  data->last_timestamp = ts;
+}
+
+// ISR
+static irqreturn_t counter_isr(int irq, void *dev_id) {
+  counter_irq_wq_data.timestamp = ktime_get();
+  schedule_work(&counter_irq_wq_data.work);
+  return IRQ_HANDLED;
+}
+
+static int dt_interrupt_probe(struct platform_device *pdev) {
+  struct device *dev = &pdev->dev;
+
+  printk("counter - interrupt probing\n");
+
+  INIT_WORK(&counter_irq_wq_data.work, counter_worker);
+  counter_irq_wq_data.client = spi_client;
+  counter_irq_wq_data.last_value = 0;
+  counter_irq_wq_data.last_timestamp = 0;
+
+  counter_interrupt = gpiod_get(dev, "intr", GPIOD_IN);
+  if (IS_ERR(counter_interrupt)) {
+    printk("counter - Error! Could not setup the GPIO intr\n");
+    return -1 * IS_ERR(counter_interrupt);
+  }
+
+  irq_number = gpiod_to_irq(counter_interrupt);
+  if (irq_number < 0) {
+    printk("counter - Error! Could not map GPIO to IRQ\n");
+    gpiod_put(counter_interrupt);
+    return irq_number;
+  }
+  printk("counter - Info! IRQ %d assigned\n", irq_number);
+
+  int ret = request_irq(irq_number, counter_isr,
+      IRQF_TRIGGER_RISING, "gpio19_irq", dev);
+  if (ret) {
+    printk("counter - Error! Could not request IRQ\n");
+    gpiod_put(counter_interrupt);
+    return ret;
+  }
+
+  printk("counter - Info! Interrupt assigned\n");
+
+  return 0;
+}
+
+static void dt_interrupt_remove(struct platform_device *pdev) {
+  printk("counter - interrupt removing\n");
+  struct device *dev = &pdev->dev;
+  free_irq(irq_number, dev);
+  gpiod_put(counter_interrupt);
+}
+
+
+
 /* module loading and unloading */
 static int __init my_init(void) {
   printk("counter - Loading the leds driver...\n");
   if(platform_driver_register(&leds_driver)) {
-    printk("dt_gpio - Error! Could not load driver\n");
+    printk("dt_gpio - Error! Could not load leds driver\n");
     return -1;
   }
 
@@ -221,6 +326,13 @@ static int __init my_init(void) {
     return -1;
   }
 
+  printk("counter - Loading the interrupt driver...\n");
+  if(platform_driver_register(&interrupt_driver)) {
+    printk("dt_gpio - Error! Could not load interrupt driver\n");
+    return -1;
+  }
+
+
   printk("counter - red led on\n");
   gpiod_set_value(red_led, 1);
 
@@ -236,6 +348,9 @@ static void __exit my_exit(void) {
 
   printk("counter - Unloading the ls7366r driver...\n");
   spi_unregister_driver(&ls7366r_driver);
+
+  printk("counter - Unloading the interrupt driver...\n");
+  platform_driver_unregister(&interrupt_driver);
 }
 
 module_init(my_init);

driver/counter.dts

@@ -6,12 +6,15 @@
     target-path = "/soc";
     __overlay__ {
       status = "okay";
-
       leds {
         compatible = "hottis,leds";
         red-led-gpio = <&gpio 26 0>; 
         blue-led-gpio = <&gpio 21 0>; 
       };
+      intr {
+        compatible = "hottis,intr";
+        intr-gpio = <&gpio 19 0>;
+      };
     };
   };