netdev - [PATCH net-next 06/12] nfp: avoid reclaiming resource mutex by mistake

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Date: Mon, 24 Jul 2023 11:48:15 +0200
From: Louis Peens <louis.peens@...igine.com>
To: David Miller <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <simon.horman@...igine.com>,
	Yinjun Zhang <yinjun.zhang@...igine.com>,
	Tianyu Yuan <tianyu.yuan@...igine.com>,
	netdev@...r.kernel.org,
	oss-drivers@...igine.com
Subject: [PATCH net-next 06/12] nfp: avoid reclaiming resource mutex by mistake

From: Yinjun Zhang <yinjun.zhang@...igine.com>

Multiple PFs of the same controller use the same interface
id. So we shouldn't unconditionally reclaim resource mutex
when probing, because the mutex may be held by another PF
from the same controller.

Now give it some time to release the mutex, and reclaim it
if timeout.

Signed-off-by: Yinjun Zhang <yinjun.zhang@...igine.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@...igine.com>
Acked-by: Simon Horman <simon.horman@...igine.com>
Signed-off-by: Louis Peens <louis.peens@...igine.com>
---
 .../netronome/nfp/nfpcore/nfp_mutex.c         | 21 +++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c
index 7bc17b94ac60..1b9170d9da77 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c
@@ -343,6 +343,7 @@ int nfp_cpp_mutex_reclaim(struct nfp_cpp *cpp, int target,
 {
 	const u32 mur = NFP_CPP_ID(target, 3, 0);	/* atomic_read */
 	const u32 muw = NFP_CPP_ID(target, 4, 0);	/* atomic_write */
+	unsigned long timeout = jiffies + 2 * HZ;
 	u16 interface = nfp_cpp_interface(cpp);
 	int err;
 	u32 tmp;
@@ -351,13 +352,21 @@ int nfp_cpp_mutex_reclaim(struct nfp_cpp *cpp, int target,
 	if (err)
 		return err;
 
-	/* Check lock */
-	err = nfp_cpp_readl(cpp, mur, address, &tmp);
-	if (err < 0)
-		return err;
+	/* Check lock. Note that PFs from the same controller use same interface ID.
+	 * So considering that the lock may be held by other PFs from the same
+	 * controller, we give it some time to release the lock, and only reclaim it
+	 * if timeout.
+	 */
+	while (time_is_after_jiffies(timeout)) {
+		err = nfp_cpp_readl(cpp, mur, address, &tmp);
+		if (err < 0)
+			return err;
 
-	if (nfp_mutex_is_unlocked(tmp) || nfp_mutex_owner(tmp) != interface)
-		return 0;
+		if (nfp_mutex_is_unlocked(tmp) || nfp_mutex_owner(tmp) != interface)
+			return 0;
+
+		msleep_interruptible(10);
+	}
 
 	/* Bust the lock */
 	err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_unlocked(interface));
-- 
2.34.1