[PATCH 10/10] gpu: host1x: Optionally block when acquiring channel

[Mikko Perttunen <mperttunen@nvidia.com>]

Add an option to host1x_channel_request to interruptibly wait for a
free channel. This allows IOCTLs that acquire a channel to block
the userspace.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
---
 drivers/gpu/drm/tegra/drm.c  |  9 +++++----
 drivers/gpu/drm/tegra/gr2d.c |  6 +++---
 drivers/gpu/drm/tegra/gr3d.c |  6 +++---
 drivers/gpu/host1x/channel.c | 40 ++++++++++++++++++++++++++++++----------
 drivers/gpu/host1x/channel.h |  1 +
 include/linux/host1x.h       |  2 +-
 6 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 658bc8814f38..19f77c1a76c0 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -389,7 +389,8 @@ static int host1x_waitchk_copy_from_user(struct host1x_waitchk *dest,
  * Request a free hardware host1x channel for this user context, or if the
  * context already has one, bump its refcount.
  *
- * Returns 0 on success, or -EBUSY if there were no free hardware channels.
+ * Returns 0 on success, -EINTR if wait for a free channel was interrupted,
+ * or other error.
  */
 int tegra_drm_context_get_channel(struct tegra_drm_context *context)
 {
@@ -398,10 +399,10 @@ int tegra_drm_context_get_channel(struct tegra_drm_context *context)
 	mutex_lock(&context->lock);
 
 	if (context->pending_jobs == 0) {
-		context->channel = host1x_channel_request(client->dev);
-		if (!context->channel) {
+		context->channel = host1x_channel_request(client->dev, true);
+		if (IS_ERR(context->channel)) {
 			mutex_unlock(&context->lock);
-			return -EBUSY;
+			return PTR_ERR(context->channel);
 		}
 	}
 
diff --git a/drivers/gpu/drm/tegra/gr2d.c b/drivers/gpu/drm/tegra/gr2d.c
index 3db3bcac48b9..c1853402f69b 100644
--- a/drivers/gpu/drm/tegra/gr2d.c
+++ b/drivers/gpu/drm/tegra/gr2d.c
@@ -32,9 +32,9 @@ static int gr2d_init(struct host1x_client *client)
 	unsigned long flags = HOST1X_SYNCPT_HAS_BASE;
 	struct gr2d *gr2d = to_gr2d(drm);
 
-	gr2d->channel = host1x_channel_request(client->dev);
-	if (!gr2d->channel)
-		return -ENOMEM;
+	gr2d->channel = host1x_channel_request(client->dev, false);
+	if (IS_ERR(gr2d->channel))
+		return PTR_ERR(gr2d->channel);
 
 	client->syncpts[0] = host1x_syncpt_request(client->dev, flags);
 	if (!client->syncpts[0]) {
diff --git a/drivers/gpu/drm/tegra/gr3d.c b/drivers/gpu/drm/tegra/gr3d.c
index 279438342c8c..793a91d577cb 100644
--- a/drivers/gpu/drm/tegra/gr3d.c
+++ b/drivers/gpu/drm/tegra/gr3d.c
@@ -42,9 +42,9 @@ static int gr3d_init(struct host1x_client *client)
 	unsigned long flags = HOST1X_SYNCPT_HAS_BASE;
 	struct gr3d *gr3d = to_gr3d(drm);
 
-	gr3d->channel = host1x_channel_request(client->dev);
-	if (!gr3d->channel)
-		return -ENOMEM;
+	gr3d->channel = host1x_channel_request(client->dev, false);
+	if (IS_ERR(gr3d->channel))
+		return PTR_ERR(gr3d->channel);
 
 	client->syncpts[0] = host1x_syncpt_request(client->dev, flags);
 	if (!client->syncpts[0]) {
diff --git a/drivers/gpu/host1x/channel.c b/drivers/gpu/host1x/channel.c
index 9d8cad12f9d8..eebcd51261df 100644
--- a/drivers/gpu/host1x/channel.c
+++ b/drivers/gpu/host1x/channel.c
@@ -43,6 +43,7 @@ int host1x_channel_list_init(struct host1x_channel_list *chlist,
 	bitmap_zero(chlist->allocated_channels, num_channels);
 
 	mutex_init(&chlist->lock);
+	sema_init(&chlist->sema, num_channels);
 
 	return 0;
 }
@@ -99,6 +100,8 @@ static void release_channel(struct kref *kref)
 	host1x_cdma_deinit(&channel->cdma);
 
 	clear_bit(channel->id, chlist->allocated_channels);
+
+	up(&chlist->sema);
 }
 
 void host1x_channel_put(struct host1x_channel *channel)
@@ -107,19 +110,30 @@ void host1x_channel_put(struct host1x_channel *channel)
 }
 EXPORT_SYMBOL(host1x_channel_put);
 
-static struct host1x_channel *acquire_unused_channel(struct host1x *host)
+static struct host1x_channel *acquire_unused_channel(struct host1x *host,
+						     bool wait)
 {
 	struct host1x_channel_list *chlist = &host->channel_list;
 	unsigned int max_channels = host->info->nb_channels;
 	unsigned int index;
+	int err;
+
+	if (wait) {
+		err = down_interruptible(&chlist->sema);
+		if (err)
+			return ERR_PTR(err);
+	} else {
+		if (down_trylock(&chlist->sema))
+			return ERR_PTR(-EBUSY);
+	}
 
 	mutex_lock(&chlist->lock);
 
 	index = find_first_zero_bit(chlist->allocated_channels, max_channels);
-	if (index >= max_channels) {
+	if (WARN(index >= max_channels, "failed to find free channel")) {
 		mutex_unlock(&chlist->lock);
 		dev_err(host->dev, "failed to find free channel\n");
-		return NULL;
+		return ERR_PTR(-EBUSY);
 	}
 
 	chlist->channels[index].id = index;
@@ -134,20 +148,26 @@ static struct host1x_channel *acquire_unused_channel(struct host1x *host)
 /**
  * host1x_channel_request() - Allocate a channel
  * @device: Host1x unit this channel will be used to send commands to
+ * @wait: Whether to wait for a free channels if all are reserved
+ *
+ * Allocates a new host1x channel for @device. If all channels are in use,
+ * and @wait is true, does an interruptible wait until one is available.
  *
- * Allocates a new host1x channel for @device. May return NULL if CDMA
- * initialization fails.
+ * If a channel was acquired, returns a pointer to it. Otherwise returns
+ * an error pointer with -EINTR if the wait was interrupted, -EBUSY
+ * if a channel could not be acquired or another error code if channel
+ * initialization failed.
  */
-struct host1x_channel *host1x_channel_request(struct device *dev)
+struct host1x_channel *host1x_channel_request(struct device *dev, bool wait)
 {
 	struct host1x *host = dev_get_drvdata(dev->parent);
 	struct host1x_channel_list *chlist = &host->channel_list;
 	struct host1x_channel *channel;
 	int err;
 
-	channel = acquire_unused_channel(host);
-	if (!channel)
-		return NULL;
+	channel = acquire_unused_channel(host, wait);
+	if (IS_ERR(channel))
+		return channel;
 
 	kref_init(&channel->refcount);
 	mutex_init(&channel->submitlock);
@@ -168,6 +188,6 @@ struct host1x_channel *host1x_channel_request(struct device *dev)
 
 	dev_err(dev, "failed to initialize channel\n");
 
-	return NULL;
+	return ERR_PTR(err);
 }
 EXPORT_SYMBOL(host1x_channel_request);
diff --git a/drivers/gpu/host1x/channel.h b/drivers/gpu/host1x/channel.h
index e68a8ae9a670..1f5cf8029b62 100644
--- a/drivers/gpu/host1x/channel.h
+++ b/drivers/gpu/host1x/channel.h
@@ -31,6 +31,7 @@ struct host1x_channel_list {
 	struct host1x_channel *channels;
 
 	struct mutex lock;
+	struct semaphore sema;
 	unsigned long *allocated_channels;
 };
 
diff --git a/include/linux/host1x.h b/include/linux/host1x.h
index f931d28a68ff..2a34905d4408 100644
--- a/include/linux/host1x.h
+++ b/include/linux/host1x.h
@@ -171,7 +171,7 @@ u32 host1x_syncpt_base_id(struct host1x_syncpt_base *base);
 struct host1x_channel;
 struct host1x_job;
 
-struct host1x_channel *host1x_channel_request(struct device *dev);
+struct host1x_channel *host1x_channel_request(struct device *dev, bool wait);
 struct host1x_channel *host1x_channel_get(struct host1x_channel *channel);
 void host1x_channel_put(struct host1x_channel *channel);
 int host1x_job_submit(struct host1x_job *job);
-- 
2.14.2

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