linux-kernel - [RFC 5/8] fpga-mgr: separate getting/locking FPGA manager

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Date:   Wed, 15 Feb 2017 10:14:18 -0600
From:   Alan Tull <atull@...nel.org>
To:     Moritz Fischer <moritz.fischer@...us.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     Alan Tull <atull@...nel.org>, linux-kernel@...r.kernel.org,
        linux-fpga@...r.kernel.org
Subject: [RFC 5/8] fpga-mgr: separate getting/locking FPGA manager

Add fpga_mgr_lock/unlock functions that get a mutex for
exclusive use.

of_fpga_mgr_get, fpga_mgr_get, and fpga_mgr_put no longer lock
the FPGA manager mutex.

This makes it more straightforward to save a reference to
a FPGA manager and only attempting to lock it when programming
the FPGA.

Signed-off-by: Alan Tull <atull@...nel.org>
---
 drivers/fpga/fpga-mgr.c       | 44 +++++++++++++++++++++++++++++++------------
 drivers/fpga/fpga-region.c    | 13 +++++++++++--
 include/linux/fpga/fpga-mgr.h |  3 +++
 3 files changed, 46 insertions(+), 14 deletions(-)

diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index b7c719a..3206a53 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -376,28 +376,19 @@ ATTRIBUTE_GROUPS(fpga_mgr);
 struct fpga_manager *__fpga_mgr_get(struct device *dev)
 {
 	struct fpga_manager *mgr;
-	int ret = -ENODEV;
 
 	mgr = to_fpga_manager(dev);
 	if (!mgr)
 		goto err_dev;
 
-	/* Get exclusive use of fpga manager */
-	if (!mutex_trylock(&mgr->ref_mutex)) {
-		ret = -EBUSY;
-		goto err_dev;
-	}
-
 	if (!try_module_get(dev->parent->driver->owner))
-		goto err_ll_mod;
+		goto err_dev;
 
 	return mgr;
 
-err_ll_mod:
-	mutex_unlock(&mgr->ref_mutex);
 err_dev:
 	put_device(dev);
-	return ERR_PTR(ret);
+	return ERR_PTR(-ENODEV);
 }
 
 static int fpga_mgr_dev_match(struct device *dev, const void *data)
@@ -457,12 +448,41 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
 void fpga_mgr_put(struct fpga_manager *mgr)
 {
 	module_put(mgr->dev.parent->driver->owner);
-	mutex_unlock(&mgr->ref_mutex);
 	put_device(&mgr->dev);
 }
 EXPORT_SYMBOL_GPL(fpga_mgr_put);
 
 /**
+ * fpga_mgr_lock - Lock FPGA manager for exclusive use
+ * @mgr:	fpga manager
+ *
+ * Given a pointer to FPGA Manager (from fpga_mgr_get() or
+ * of_fpga_mgr_put() attempt to get the mutex).
+ *
+ * Return: 0 for success or -EBUSY
+ */
+int fpga_mgr_lock(struct fpga_manager *mgr)
+{
+	if (!mutex_trylock(&mgr->ref_mutex)) {
+		dev_err(&mgr->dev, "FPGA manager is in use.\n");
+		return -EBUSY;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_lock);
+
+/**
+ * fpga_mgr_unlock - Unlock FPGA manager
+ * @mgr:	fpga manager
+ */
+void fpga_mgr_unlock(struct fpga_manager *mgr)
+{
+	mutex_unlock(&mgr->ref_mutex);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
+
+/**
  * fpga_mgr_register - register a low level fpga manager driver
  * @dev:	fpga manager device from pdev
  * @name:	fpga manager name
diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
index 3a36417..a5d8112 100644
--- a/drivers/fpga/fpga-region.c
+++ b/drivers/fpga/fpga-region.c
@@ -142,7 +142,7 @@ static void fpga_region_put(struct fpga_region *region)
 }
 
 /**
- * fpga_region_get_manager - get exclusive reference for FPGA manager
+ * fpga_region_get_manager - get reference for FPGA manager
  * @region: FPGA region
  *
  * Get FPGA Manager from "fpga-mgr" property or from ancestor region.
@@ -265,10 +265,16 @@ static int fpga_region_program_fpga(struct fpga_region *region,
 		return PTR_ERR(mgr);
 	}
 
+	ret = fpga_mgr_lock(mgr);
+	if (ret) {
+		pr_err("FPGA manager is busy\n");
+		goto err_put_mgr;
+	}
+
 	ret = fpga_region_get_bridges(region, reg_ovl);
 	if (ret) {
 		pr_err("failed to get fpga region bridges\n");
-		goto err_put_mgr;
+		goto err_unlock_mgr;
 	}
 
 	ret = fpga_bridges_disable(&region->bridge_list);
@@ -289,6 +295,7 @@ static int fpga_region_program_fpga(struct fpga_region *region,
 		goto err_put_br;
 	}
 
+	fpga_mgr_unlock(mgr);
 	fpga_mgr_put(mgr);
 	fpga_region_put(region);
 
@@ -296,6 +303,8 @@ static int fpga_region_program_fpga(struct fpga_region *region,
 
 err_put_br:
 	fpga_bridges_put(&region->bridge_list);
+err_unlock_mgr:
+	fpga_mgr_unlock(mgr);
 err_put_mgr:
 	fpga_mgr_put(mgr);
 	fpga_region_put(region);
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index 45df05a..ae970ca 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -149,6 +149,9 @@ int fpga_mgr_firmware_load(struct fpga_manager *mgr,
 
 int fpga_mgr_load(struct fpga_manager *mgr, struct fpga_image_info *info);
 
+int fpga_mgr_lock(struct fpga_manager *mgr);
+void fpga_mgr_unlock(struct fpga_manager *mgr);
+
 struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
 
 struct fpga_manager *fpga_mgr_get(struct device *dev);
-- 
2.7.4