Date:   Tue, 21 Mar 2017 17:59:10 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     netdev@...r.kernel.org
Cc:     oss-drivers@...ronome.com, kubakici@...pl,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net-next 04/15] nfp: move mutex code out of nfp_cppcore.c

After mutex cache removal we can put the mutex code in a separate
source file.  This makes it clear it doesn't play with internals
of struct nfp_cpp any more.

No functional changes.

Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 drivers/net/ethernet/netronome/nfp/Makefile        |   1 +
 .../ethernet/netronome/nfp/nfpcore/nfp_cppcore.c   | 304 ------------------
 .../net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c | 345 +++++++++++++++++++++
 3 files changed, 346 insertions(+), 304 deletions(-)
 create mode 100644 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c

diff --git a/drivers/net/ethernet/netronome/nfp/Makefile b/drivers/net/ethernet/netronome/nfp/Makefile
index 6933afa69df2..4a5d13ef92a4 100644
--- a/drivers/net/ethernet/netronome/nfp/Makefile
+++ b/drivers/net/ethernet/netronome/nfp/Makefile
@@ -6,6 +6,7 @@ nfp-objs := \
 	    nfpcore/nfp_cpplib.o \
 	    nfpcore/nfp_hwinfo.o \
 	    nfpcore/nfp_mip.o \
+	    nfpcore/nfp_mutex.o \
 	    nfpcore/nfp_nffw.o \
 	    nfpcore/nfp_nsp.o \
 	    nfpcore/nfp_nsp_eth.o \
diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
index 6337342c5b62..62aa7bcee93d 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
@@ -65,14 +65,6 @@ struct nfp_cpp_resource {
 	u64 end;
 };
 
-struct nfp_cpp_mutex {
-	struct nfp_cpp *cpp;
-	int target;
-	u16 depth;
-	unsigned long long address;
-	u32 key;
-};
-
 struct nfp_cpp {
 	struct device dev;
 
@@ -1403,299 +1395,3 @@ void *nfp_cpp_explicit_priv(struct nfp_cpp_explicit *cpp_explicit)
 {
 	return &cpp_explicit[1];
 }
-
-/* THIS FUNCTION IS NOT EXPORTED */
-static u32 nfp_mutex_locked(u16 interface)
-{
-	return (u32)interface << 16 | 0x000f;
-}
-
-static u32 nfp_mutex_unlocked(u16 interface)
-{
-	return (u32)interface << 16 | 0x0000;
-}
-
-static bool nfp_mutex_is_locked(u32 val)
-{
-	return (val & 0xffff) == 0x000f;
-}
-
-static bool nfp_mutex_is_unlocked(u32 val)
-{
-	return (val & 0xffff) == 0000;
-}
-
-/* If you need more than 65536 recursive locks, please rethink your code. */
-#define MUTEX_DEPTH_MAX         0xffff
-
-static int
-nfp_cpp_mutex_validate(u16 interface, int *target, unsigned long long address)
-{
-	/* Not permitted on invalid interfaces */
-	if (NFP_CPP_INTERFACE_TYPE_of(interface) ==
-	    NFP_CPP_INTERFACE_TYPE_INVALID)
-		return -EINVAL;
-
-	/* Address must be 64-bit aligned */
-	if (address & 7)
-		return -EINVAL;
-
-	if (*target != NFP_CPP_TARGET_MU)
-		return -EINVAL;
-
-	return 0;
-}
-
-/**
- * nfp_cpp_mutex_init() - Initialize a mutex location
- * @cpp:	NFP CPP handle
- * @target:	NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
- * @address:	Offset into the address space of the NFP CPP target ID
- * @key:	Unique 32-bit value for this mutex
- *
- * The CPP target:address must point to a 64-bit aligned location, and
- * will initialize 64 bits of data at the location.
- *
- * This creates the initial mutex state, as locked by this
- * nfp_cpp_interface().
- *
- * This function should only be called when setting up
- * the initial lock state upon boot-up of the system.
- *
- * Return: 0 on success, or -errno on failure
- */
-int nfp_cpp_mutex_init(struct nfp_cpp *cpp,
-		       int target, unsigned long long address, u32 key)
-{
-	const u32 muw = NFP_CPP_ID(target, 4, 0);    /* atomic_write */
-	u16 interface = nfp_cpp_interface(cpp);
-	int err;
-
-	err = nfp_cpp_mutex_validate(interface, &target, address);
-	if (err)
-		return err;
-
-	err = nfp_cpp_writel(cpp, muw, address + 4, key);
-	if (err)
-		return err;
-
-	err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_locked(interface));
-	if (err)
-		return err;
-
-	return 0;
-}
-
-/**
- * nfp_cpp_mutex_alloc() - Create a mutex handle
- * @cpp:	NFP CPP handle
- * @target:	NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
- * @address:	Offset into the address space of the NFP CPP target ID
- * @key:	32-bit unique key (must match the key at this location)
- *
- * The CPP target:address must point to a 64-bit aligned location, and
- * reserve 64 bits of data at the location for use by the handle.
- *
- * Only target/address pairs that point to entities that support the
- * MU Atomic Engine's CmpAndSwap32 command are supported.
- *
- * Return:	A non-NULL struct nfp_cpp_mutex * on success, NULL on failure.
- */
-struct nfp_cpp_mutex *nfp_cpp_mutex_alloc(struct nfp_cpp *cpp, int target,
-					  unsigned long long address, u32 key)
-{
-	const u32 mur = NFP_CPP_ID(target, 3, 0);    /* atomic_read */
-	u16 interface = nfp_cpp_interface(cpp);
-	struct nfp_cpp_mutex *mutex;
-	int err;
-	u32 tmp;
-
-	err = nfp_cpp_mutex_validate(interface, &target, address);
-	if (err)
-		return NULL;
-
-	err = nfp_cpp_readl(cpp, mur, address + 4, &tmp);
-	if (err < 0)
-		return NULL;
-
-	if (tmp != key)
-		return NULL;
-
-	mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
-	if (!mutex)
-		return NULL;
-
-	mutex->cpp = cpp;
-	mutex->target = target;
-	mutex->address = address;
-	mutex->key = key;
-	mutex->depth = 0;
-
-	return mutex;
-}
-
-/**
- * nfp_cpp_mutex_free() - Free a mutex handle - does not alter the lock state
- * @mutex:	NFP CPP Mutex handle
- */
-void nfp_cpp_mutex_free(struct nfp_cpp_mutex *mutex)
-{
-	kfree(mutex);
-}
-
-/**
- * nfp_cpp_mutex_lock() - Lock a mutex handle, using the NFP MU Atomic Engine
- * @mutex:	NFP CPP Mutex handle
- *
- * Return: 0 on success, or -errno on failure
- */
-int nfp_cpp_mutex_lock(struct nfp_cpp_mutex *mutex)
-{
-	unsigned long warn_at = jiffies + 15 * HZ;
-	unsigned int timeout_ms = 1;
-	int err;
-
-	/* We can't use a waitqueue here, because the unlocker
-	 * might be on a separate CPU.
-	 *
-	 * So just wait for now.
-	 */
-	for (;;) {
-		err = nfp_cpp_mutex_trylock(mutex);
-		if (err != -EBUSY)
-			break;
-
-		err = msleep_interruptible(timeout_ms);
-		if (err != 0)
-			return -ERESTARTSYS;
-
-		if (time_is_before_eq_jiffies(warn_at)) {
-			warn_at = jiffies + 60 * HZ;
-			dev_warn(mutex->cpp->dev.parent,
-				 "Warning: waiting for NFP mutex [depth:%hd target:%d addr:%llx key:%08x]\n",
-				 mutex->depth,
-				 mutex->target, mutex->address, mutex->key);
-		}
-	}
-
-	return err;
-}
-
-/**
- * nfp_cpp_mutex_unlock() - Unlock a mutex handle, using the MU Atomic Engine
- * @mutex:	NFP CPP Mutex handle
- *
- * Return: 0 on success, or -errno on failure
- */
-int nfp_cpp_mutex_unlock(struct nfp_cpp_mutex *mutex)
-{
-	const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
-	const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
-	struct nfp_cpp *cpp = mutex->cpp;
-	u32 key, value;
-	u16 interface;
-	int err;
-
-	interface = nfp_cpp_interface(cpp);
-
-	if (mutex->depth > 1) {
-		mutex->depth--;
-		return 0;
-	}
-
-	err = nfp_cpp_readl(mutex->cpp, mur, mutex->address + 4, &key);
-	if (err < 0)
-		return err;
-
-	if (key != mutex->key)
-		return -EPERM;
-
-	err = nfp_cpp_readl(mutex->cpp, mur, mutex->address, &value);
-	if (err < 0)
-		return err;
-
-	if (value != nfp_mutex_locked(interface))
-		return -EACCES;
-
-	err = nfp_cpp_writel(cpp, muw, mutex->address,
-			     nfp_mutex_unlocked(interface));
-	if (err < 0)
-		return err;
-
-	mutex->depth = 0;
-	return 0;
-}
-
-/**
- * nfp_cpp_mutex_trylock() - Attempt to lock a mutex handle
- * @mutex:	NFP CPP Mutex handle
- *
- * Return:      0 if the lock succeeded, -errno on failure
- */
-int nfp_cpp_mutex_trylock(struct nfp_cpp_mutex *mutex)
-{
-	const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
-	const u32 mus = NFP_CPP_ID(mutex->target, 5, 3);    /* test_set_imm */
-	const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
-	struct nfp_cpp *cpp = mutex->cpp;
-	u32 key, value, tmp;
-	int err;
-
-	if (mutex->depth > 0) {
-		if (mutex->depth == MUTEX_DEPTH_MAX)
-			return -E2BIG;
-		mutex->depth++;
-		return 0;
-	}
-
-	/* Verify that the lock marker is not damaged */
-	err = nfp_cpp_readl(cpp, mur, mutex->address + 4, &key);
-	if (err < 0)
-		return err;
-
-	if (key != mutex->key)
-		return -EPERM;
-
-	/* Compare against the unlocked state, and if true,
-	 * write the interface id into the top 16 bits, and
-	 * mark as locked.
-	 */
-	value = nfp_mutex_locked(nfp_cpp_interface(cpp));
-
-	/* We use test_set_imm here, as it implies a read
-	 * of the current state, and sets the bits in the
-	 * bytemask of the command to 1s. Since the mutex
-	 * is guaranteed to be 64-bit aligned, the bytemask
-	 * of this 32-bit command is ensured to be 8'b00001111,
-	 * which implies that the lower 4 bits will be set to
-	 * ones regardless of the initial state.
-	 *
-	 * Since this is a 'Readback' operation, with no Pull
-	 * data, we can treat this as a normal Push (read)
-	 * atomic, which returns the original value.
-	 */
-	err = nfp_cpp_readl(cpp, mus, mutex->address, &tmp);
-	if (err < 0)
-		return err;
-
-	/* Was it unlocked? */
-	if (nfp_mutex_is_unlocked(tmp)) {
-		/* The read value can only be 0x....0000 in the unlocked state.
-		 * If there was another contending for this lock, then
-		 * the lock state would be 0x....000f
-		 */
-
-		/* Write our owner ID into the lock
-		 * While not strictly necessary, this helps with
-		 * debug and bookkeeping.
-		 */
-		err = nfp_cpp_writel(cpp, muw, mutex->address, value);
-		if (err < 0)
-			return err;
-
-		mutex->depth = 1;
-		return 0;
-	}
-
-	return nfp_mutex_is_locked(tmp) ? -EBUSY : -EINVAL;
-}
diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c
new file mode 100644
index 000000000000..8a99c189efa8
--- /dev/null
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c
@@ -0,0 +1,345 @@
+/*
+ * Copyright (C) 2015-2017 Netronome Systems, Inc.
+ *
+ * This software is dual licensed under the GNU General License Version 2,
+ * June 1991 as shown in the file COPYING in the top-level directory of this
+ * source tree or the BSD 2-Clause License provided below.  You have the
+ * option to license this software under the complete terms of either license.
+ *
+ * The BSD 2-Clause License:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      1. Redistributions of source code must retain the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer.
+ *
+ *      2. Redistributions in binary form must reproduce the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer in the documentation and/or other materials
+ *         provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/jiffies.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+
+#include "nfp_cpp.h"
+#include "nfp6000/nfp6000.h"
+
+struct nfp_cpp_mutex {
+	struct nfp_cpp *cpp;
+	int target;
+	u16 depth;
+	unsigned long long address;
+	u32 key;
+};
+
+static u32 nfp_mutex_locked(u16 interface)
+{
+	return (u32)interface << 16 | 0x000f;
+}
+
+static u32 nfp_mutex_unlocked(u16 interface)
+{
+	return (u32)interface << 16 | 0x0000;
+}
+
+static bool nfp_mutex_is_locked(u32 val)
+{
+	return (val & 0xffff) == 0x000f;
+}
+
+static bool nfp_mutex_is_unlocked(u32 val)
+{
+	return (val & 0xffff) == 0000;
+}
+
+/* If you need more than 65536 recursive locks, please rethink your code. */
+#define NFP_MUTEX_DEPTH_MAX         0xffff
+
+static int
+nfp_cpp_mutex_validate(u16 interface, int *target, unsigned long long address)
+{
+	/* Not permitted on invalid interfaces */
+	if (NFP_CPP_INTERFACE_TYPE_of(interface) ==
+	    NFP_CPP_INTERFACE_TYPE_INVALID)
+		return -EINVAL;
+
+	/* Address must be 64-bit aligned */
+	if (address & 7)
+		return -EINVAL;
+
+	if (*target != NFP_CPP_TARGET_MU)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * nfp_cpp_mutex_init() - Initialize a mutex location
+ * @cpp:	NFP CPP handle
+ * @target:	NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
+ * @address:	Offset into the address space of the NFP CPP target ID
+ * @key:	Unique 32-bit value for this mutex
+ *
+ * The CPP target:address must point to a 64-bit aligned location, and
+ * will initialize 64 bits of data at the location.
+ *
+ * This creates the initial mutex state, as locked by this
+ * nfp_cpp_interface().
+ *
+ * This function should only be called when setting up
+ * the initial lock state upon boot-up of the system.
+ *
+ * Return: 0 on success, or -errno on failure
+ */
+int nfp_cpp_mutex_init(struct nfp_cpp *cpp,
+		       int target, unsigned long long address, u32 key)
+{
+	const u32 muw = NFP_CPP_ID(target, 4, 0);    /* atomic_write */
+	u16 interface = nfp_cpp_interface(cpp);
+	int err;
+
+	err = nfp_cpp_mutex_validate(interface, &target, address);
+	if (err)
+		return err;
+
+	err = nfp_cpp_writel(cpp, muw, address + 4, key);
+	if (err)
+		return err;
+
+	err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_locked(interface));
+	if (err)
+		return err;
+
+	return 0;
+}
+
+/**
+ * nfp_cpp_mutex_alloc() - Create a mutex handle
+ * @cpp:	NFP CPP handle
+ * @target:	NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
+ * @address:	Offset into the address space of the NFP CPP target ID
+ * @key:	32-bit unique key (must match the key at this location)
+ *
+ * The CPP target:address must point to a 64-bit aligned location, and
+ * reserve 64 bits of data at the location for use by the handle.
+ *
+ * Only target/address pairs that point to entities that support the
+ * MU Atomic Engine's CmpAndSwap32 command are supported.
+ *
+ * Return:	A non-NULL struct nfp_cpp_mutex * on success, NULL on failure.
+ */
+struct nfp_cpp_mutex *nfp_cpp_mutex_alloc(struct nfp_cpp *cpp, int target,
+					  unsigned long long address, u32 key)
+{
+	const u32 mur = NFP_CPP_ID(target, 3, 0);    /* atomic_read */
+	u16 interface = nfp_cpp_interface(cpp);
+	struct nfp_cpp_mutex *mutex;
+	int err;
+	u32 tmp;
+
+	err = nfp_cpp_mutex_validate(interface, &target, address);
+	if (err)
+		return NULL;
+
+	err = nfp_cpp_readl(cpp, mur, address + 4, &tmp);
+	if (err < 0)
+		return NULL;
+
+	if (tmp != key)
+		return NULL;
+
+	mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
+	if (!mutex)
+		return NULL;
+
+	mutex->cpp = cpp;
+	mutex->target = target;
+	mutex->address = address;
+	mutex->key = key;
+	mutex->depth = 0;
+
+	return mutex;
+}
+
+/**
+ * nfp_cpp_mutex_free() - Free a mutex handle - does not alter the lock state
+ * @mutex:	NFP CPP Mutex handle
+ */
+void nfp_cpp_mutex_free(struct nfp_cpp_mutex *mutex)
+{
+	kfree(mutex);
+}
+
+/**
+ * nfp_cpp_mutex_lock() - Lock a mutex handle, using the NFP MU Atomic Engine
+ * @mutex:	NFP CPP Mutex handle
+ *
+ * Return: 0 on success, or -errno on failure
+ */
+int nfp_cpp_mutex_lock(struct nfp_cpp_mutex *mutex)
+{
+	unsigned long warn_at = jiffies + 15 * HZ;
+	unsigned int timeout_ms = 1;
+	int err;
+
+	/* We can't use a waitqueue here, because the unlocker
+	 * might be on a separate CPU.
+	 *
+	 * So just wait for now.
+	 */
+	for (;;) {
+		err = nfp_cpp_mutex_trylock(mutex);
+		if (err != -EBUSY)
+			break;
+
+		err = msleep_interruptible(timeout_ms);
+		if (err != 0)
+			return -ERESTARTSYS;
+
+		if (time_is_before_eq_jiffies(warn_at)) {
+			warn_at = jiffies + 60 * HZ;
+			nfp_warn(mutex->cpp,
+				 "Warning: waiting for NFP mutex [depth:%hd target:%d addr:%llx key:%08x]\n",
+				 mutex->depth,
+				 mutex->target, mutex->address, mutex->key);
+		}
+	}
+
+	return err;
+}
+
+/**
+ * nfp_cpp_mutex_unlock() - Unlock a mutex handle, using the MU Atomic Engine
+ * @mutex:	NFP CPP Mutex handle
+ *
+ * Return: 0 on success, or -errno on failure
+ */
+int nfp_cpp_mutex_unlock(struct nfp_cpp_mutex *mutex)
+{
+	const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
+	const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
+	struct nfp_cpp *cpp = mutex->cpp;
+	u32 key, value;
+	u16 interface;
+	int err;
+
+	interface = nfp_cpp_interface(cpp);
+
+	if (mutex->depth > 1) {
+		mutex->depth--;
+		return 0;
+	}
+
+	err = nfp_cpp_readl(mutex->cpp, mur, mutex->address + 4, &key);
+	if (err < 0)
+		return err;
+
+	if (key != mutex->key)
+		return -EPERM;
+
+	err = nfp_cpp_readl(mutex->cpp, mur, mutex->address, &value);
+	if (err < 0)
+		return err;
+
+	if (value != nfp_mutex_locked(interface))
+		return -EACCES;
+
+	err = nfp_cpp_writel(cpp, muw, mutex->address,
+			     nfp_mutex_unlocked(interface));
+	if (err < 0)
+		return err;
+
+	mutex->depth = 0;
+	return 0;
+}
+
+/**
+ * nfp_cpp_mutex_trylock() - Attempt to lock a mutex handle
+ * @mutex:	NFP CPP Mutex handle
+ *
+ * Return:      0 if the lock succeeded, -errno on failure
+ */
+int nfp_cpp_mutex_trylock(struct nfp_cpp_mutex *mutex)
+{
+	const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
+	const u32 mus = NFP_CPP_ID(mutex->target, 5, 3);    /* test_set_imm */
+	const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
+	struct nfp_cpp *cpp = mutex->cpp;
+	u32 key, value, tmp;
+	int err;
+
+	if (mutex->depth > 0) {
+		if (mutex->depth == NFP_MUTEX_DEPTH_MAX)
+			return -E2BIG;
+		mutex->depth++;
+		return 0;
+	}
+
+	/* Verify that the lock marker is not damaged */
+	err = nfp_cpp_readl(cpp, mur, mutex->address + 4, &key);
+	if (err < 0)
+		return err;
+
+	if (key != mutex->key)
+		return -EPERM;
+
+	/* Compare against the unlocked state, and if true,
+	 * write the interface id into the top 16 bits, and
+	 * mark as locked.
+	 */
+	value = nfp_mutex_locked(nfp_cpp_interface(cpp));
+
+	/* We use test_set_imm here, as it implies a read
+	 * of the current state, and sets the bits in the
+	 * bytemask of the command to 1s. Since the mutex
+	 * is guaranteed to be 64-bit aligned, the bytemask
+	 * of this 32-bit command is ensured to be 8'b00001111,
+	 * which implies that the lower 4 bits will be set to
+	 * ones regardless of the initial state.
+	 *
+	 * Since this is a 'Readback' operation, with no Pull
+	 * data, we can treat this as a normal Push (read)
+	 * atomic, which returns the original value.
+	 */
+	err = nfp_cpp_readl(cpp, mus, mutex->address, &tmp);
+	if (err < 0)
+		return err;
+
+	/* Was it unlocked? */
+	if (nfp_mutex_is_unlocked(tmp)) {
+		/* The read value can only be 0x....0000 in the unlocked state.
+		 * If there was another contending for this lock, then
+		 * the lock state would be 0x....000f
+		 */
+
+		/* Write our owner ID into the lock
+		 * While not strictly necessary, this helps with
+		 * debug and bookkeeping.
+		 */
+		err = nfp_cpp_writel(cpp, muw, mutex->address, value);
+		if (err < 0)
+			return err;
+
+		mutex->depth = 1;
+		return 0;
+	}
+
+	return nfp_mutex_is_locked(tmp) ? -EBUSY : -EINVAL;
+}
-- 
2.11.0

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