drm/udl: Replace semaphore with a simple wait queue

UDL driver uses a semaphore for controlling the emptiness of FIFO in a
slightly funky way.  This patch replaces it with a wait queue and
controls the emptiness with the standard wait_event*() macro instead,
which is a more straightforward implementation.

While we are at it, drop the dead code for delayed semaphore down,
too.

Tested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220804075826.27036-2-tiwai@suse.de

diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
index cc16a13316e4e1f565331449b6ee17b6cee3b543..e008686ec738ed4bf46cc449402c908ddb120083 100644 (file)
--- a/drivers/gpu/drm/udl/udl_drv.h
+++ b/drivers/gpu/drm/udl/udl_drv.h
@@ -34,14 +34,13 @@ struct udl_device;
 struct urb_node {
        struct list_head entry;
        struct udl_device *dev;
-       struct delayed_work release_urb_work;
        struct urb *urb;
 };
 
 struct urb_list {
        struct list_head list;
        spinlock_t lock;
-       struct semaphore limit_sem;
+       wait_queue_head_t sleep;
        int available;
        int count;
        size_t size;
@@ -75,7 +74,13 @@ static inline struct usb_device *udl_to_usb_device(struct udl_device *udl)
 int udl_modeset_init(struct drm_device *dev);
 struct drm_connector *udl_connector_init(struct drm_device *dev);
 
-struct urb *udl_get_urb(struct drm_device *dev);
+struct urb *udl_get_urb_timeout(struct drm_device *dev, long timeout);
+
+#define GET_URB_TIMEOUT        HZ
+static inline struct urb *udl_get_urb(struct drm_device *dev)
+{
+       return udl_get_urb_timeout(dev, GET_URB_TIMEOUT);
+}
 
 int udl_submit_urb(struct drm_device *dev, struct urb *urb, size_t len);
 void udl_urb_completion(struct urb *urb);

diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
index 853f147036f6b5c5ecda9598c0bbd8d0f010a8d0..67fd41e59b805781316405a64d5cbb7152fa1d8c 100644 (file)
--- a/drivers/gpu/drm/udl/udl_main.c
+++ b/drivers/gpu/drm/udl/udl_main.c
@@ -23,9 +23,6 @@
 #define WRITES_IN_FLIGHT (4)
 #define MAX_VENDOR_DESCRIPTOR_SIZE 256
 
-#define GET_URB_TIMEOUT        HZ
-#define FREE_URB_TIMEOUT (HZ*2)
-
 static int udl_parse_vendor_descriptor(struct udl_device *udl)
 {
        struct usb_device *udev = udl_to_usb_device(udl);
@@ -119,14 +116,6 @@ static int udl_select_std_channel(struct udl_device *udl)
        return ret < 0 ? ret : 0;
 }
 
-static void udl_release_urb_work(struct work_struct *work)
-{
-       struct urb_node *unode = container_of(work, struct urb_node,
-                                             release_urb_work.work);
-
-       up(&unode->dev->urbs.limit_sem);
-}
-
 void udl_urb_completion(struct urb *urb)
 {
        struct urb_node *unode = urb->context;
@@ -150,23 +139,13 @@ void udl_urb_completion(struct urb *urb)
        udl->urbs.available++;
        spin_unlock_irqrestore(&udl->urbs.lock, flags);
 
-#if 0
-       /*
-        * When using fb_defio, we deadlock if up() is called
-        * while another is waiting. So queue to another process.
-        */
-       if (fb_defio)
-               schedule_delayed_work(&unode->release_urb_work, 0);
-       else
-#endif
-               up(&udl->urbs.limit_sem);
+       wake_up(&udl->urbs.sleep);
 }
 
 static void udl_free_urb_list(struct drm_device *dev)
 {
        struct udl_device *udl = to_udl(dev);
        int count = udl->urbs.count;
-       struct list_head *node;
        struct urb_node *unode;
        struct urb *urb;
 
@@ -174,23 +153,15 @@ static void udl_free_urb_list(struct drm_device *dev)
 
        /* keep waiting and freeing, until we've got 'em all */
        while (count--) {
-               down(&udl->urbs.limit_sem);
-
-               spin_lock_irq(&udl->urbs.lock);
-
-               node = udl->urbs.list.next; /* have reserved one with sem */
-               list_del_init(node);
-
-               spin_unlock_irq(&udl->urbs.lock);
-
-               unode = list_entry(node, struct urb_node, entry);
-               urb = unode->urb;
-
+               urb = udl_get_urb_timeout(dev, MAX_SCHEDULE_TIMEOUT);
+               if (WARN_ON(!urb))
+                       break;
+               unode = urb->context;
                /* Free each separately allocated piece */
                usb_free_coherent(urb->dev, udl->urbs.size,
                                  urb->transfer_buffer, urb->transfer_dma);
                usb_free_urb(urb);
-               kfree(node);
+               kfree(unode);
        }
        udl->urbs.count = 0;
 }
@@ -210,7 +181,7 @@ retry:
        udl->urbs.size = size;
        INIT_LIST_HEAD(&udl->urbs.list);
 
-       sema_init(&udl->urbs.limit_sem, 0);
+       init_waitqueue_head(&udl->urbs.sleep);
        udl->urbs.count = 0;
        udl->urbs.available = 0;
 
@@ -220,9 +191,6 @@ retry:
                        break;
                unode->dev = udl;
 
-               INIT_DELAYED_WORK(&unode->release_urb_work,
-                         udl_release_urb_work);
-
                urb = usb_alloc_urb(0, GFP_KERNEL);
                if (!urb) {
                        kfree(unode);
@@ -250,7 +218,6 @@ retry:
 
                list_add_tail(&unode->entry, &udl->urbs.list);
 
-               up(&udl->urbs.limit_sem);
                udl->urbs.count++;
                udl->urbs.available++;
        }
@@ -260,36 +227,31 @@ retry:
        return udl->urbs.count;
 }
 
-struct urb *udl_get_urb(struct drm_device *dev)
+struct urb *udl_get_urb_timeout(struct drm_device *dev, long timeout)
 {
        struct udl_device *udl = to_udl(dev);
-       int ret = 0;
-       struct list_head *entry;
-       struct urb_node *unode;
-       struct urb *urb = NULL;
+       struct urb_node *unode = NULL;
 
-       /* Wait for an in-flight buffer to complete and get re-queued */
-       ret = down_timeout(&udl->urbs.limit_sem, GET_URB_TIMEOUT);
-       if (ret) {
-               DRM_INFO("wait for urb interrupted: %x available: %d\n",
-                      ret, udl->urbs.available);
-               goto error;
-       }
+       if (!udl->urbs.count)
+               return NULL;
 
+       /* Wait for an in-flight buffer to complete and get re-queued */
        spin_lock_irq(&udl->urbs.lock);
+       if (!wait_event_lock_irq_timeout(udl->urbs.sleep,
+                                        !list_empty(&udl->urbs.list),
+                                        udl->urbs.lock, timeout)) {
+               DRM_INFO("wait for urb interrupted: available: %d\n",
+                        udl->urbs.available);
+               goto unlock;
+       }
 
-       BUG_ON(list_empty(&udl->urbs.list)); /* reserved one with limit_sem */
-       entry = udl->urbs.list.next;
-       list_del_init(entry);
+       unode = list_first_entry(&udl->urbs.list, struct urb_node, entry);
+       list_del_init(&unode->entry);
        udl->urbs.available--;
 
+unlock:
        spin_unlock_irq(&udl->urbs.lock);
-
-       unode = list_entry(entry, struct urb_node, entry);
-       urb = unode->urb;
-
-error:
-       return urb;
+       return unode ? unode->urb : NULL;
 }
 
 int udl_submit_urb(struct drm_device *dev, struct urb *urb, size_t len)