commit 6283b26668fed907d3709bcad446665321fc8bf1
author Austin Schuh <austin.linux@gmail.com> Sat Dec 31 23:11:15 2022 -0800
committer Austin Schuh <austin.linux@gmail.com> Sun Jan 01 13:38:30 2023 -0800
tree 712e000ee9c92b485d131fb6a23c505629f0dbdc
parent ba7d5de86e6a5f0782cecf9c1087b4fcfe2f9244

Make adis16505 driver work for the rockpi

New kernel has a slightly different API.

We also want to leave the driver probed all the time.  So, set
everything up, and disable interrupts until userspace opens the device.
This makes it safe to probe everywhere.

Change-Id: Ia7044b9d9c9a502dc9fd112bd1cf2a62ee375055
Signed-off-by: Austin Schuh <austin.linux@gmail.com>

y2022/localizer/kernel/adis16505.c

diff --git a/y2022/localizer/kernel/adis16505.c b/y2022/localizer/kernel/adis16505.c
index a91006e..963ca4a 100644
--- a/y2022/localizer/kernel/adis16505.c
+++ b/y2022/localizer/kernel/adis16505.c
@@ -49,7 +49,7 @@
   char tx_buff[128];
   char rx_buff[128];
 
-  int count;
+  atomic_t count;
 
   spinlock_t lock;
 
@@ -62,21 +62,18 @@
 static int adis16505_dev_open(struct inode *in, struct file *f) {
   struct adis16505_state *ts =
       container_of(in->i_cdev, struct adis16505_state, handle_cdev);
-  int count;
+  int count = 0;
 
   f->private_data = ts;
+  count = atomic_cmpxchg(&ts->count, 0, 1);
 
-  spin_lock(&ts->lock);
-  count = ts->count;
-  if (count == 0) {
-    ++(ts->count);
-  }
-  spin_unlock(&ts->lock);
-
-  printk("open %p, count %d\n", ts, count);
   if (count > 0) {
     return -EBUSY;
   }
+
+  // Enable the IRQ after we've declared the device open.
+  enable_irq(ts->spi->irq);
+
   return 0;
 }
 
@@ -84,10 +81,13 @@
   struct adis16505_state *ts;
   ts = container_of(in->i_cdev, struct adis16505_state, handle_cdev);
 
-  printk("release %p\n", ts);
-  spin_lock(&ts->lock);
-  --(ts->count);
-  spin_unlock(&ts->lock);
+  // Disable before declaring ourselves closed so we don't fire the IRQ when we
+  // are disabled, or let someone else open it up again before we disable it.
+  disable_irq(ts->spi->irq);
+
+  if (atomic_cmpxchg(&ts->count, 1, 0) != 1) {
+    BUG_ON(true);
+  }
 
   return 0;
 }
@@ -230,7 +230,7 @@
 
   spin_lock_init(&ts->lock);
   spin_lock_init(&ts->fifo_read_lock);
-  ts->count = 0;
+  atomic_set(&ts->count, 0);
   INIT_KFIFO(ts->fifo);
   init_waitqueue_head(&ts->wq);
 
@@ -241,11 +241,20 @@
   err = request_threaded_irq(spi->irq, NULL, adis16505_irq, IRQF_ONESHOT,
                              spi->dev.driver->name, ts);
 
-  if (!ts) {
+  if (err < 0) {
     dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
     goto err_free_mem;
   }
 
+  // Immediately disable the IRQ.  Opening the device will enable it, so this
+  // lets us leave the driver probed all the time and only use it when userspace
+  // asks.
+  //
+  // Note: the IRQ will fire probably once before we get it disabled...  It
+  // might initiate a transfer from a device which isn't connected, which should
+  // just return 0 for everything.  This isn't actually a huge concern.
+  disable_irq(spi->irq);
+
   err = alloc_chrdev_region(&ts->character_device, 0, 1, "adis16505");
   if (err < 0) {
     dev_dbg(&spi->dev, "alloc_chrdev_region error %i", err);
@@ -295,7 +304,7 @@
   return err;
 }
 
-static int adis16505_remove(struct spi_device *spi) {
+static void adis16505_remove(struct spi_device *spi) {
   struct adis16505_state *ts = spi_get_drvdata(spi);
 
   device_destroy(ts->device_class, ts->character_device);
@@ -309,7 +318,6 @@
   kfree(ts);
 
   dev_dbg(&spi->dev, "unregistered adis16505\n");
-  return 0;
 }
 
 static struct spi_driver adis16505_driver = {