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From: Eddie James <eajames@linux.ibm.com>
To: linux-fsi@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
        devicetree@vger.kernel.org, andi.shyti@kernel.org,
        eajames@linux.ibm.com, alistair@popple.id.au, joel@jms.id.au,
        jk@ozlabs.org, robh@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, lakshmiy@us.ibmcom
Subject: [PATCH v2 10/31] fsi: core: Add slave spinlock
Date: Mon, 26 Feb 2024 10:53:00 -0600
Message-Id: <20240226165321.91976-11-eajames@linux.ibm.com>
In-Reply-To: <20240226165321.91976-1-eajames@linux.ibm.com>
References: <20240226165321.91976-1-eajames@linux.ibm.com>
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FSI slave operations were not locked, meaning that during slave
error recovery operations, other slave accesses may take place,
resulting in incorrect recovery and additional errors. Make the
slave access and error recovery atomic with a spinlock. Don't
use a mutex for future interrupt handling support.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/fsi/fsi-core.c  | 7 +++++++
 drivers/fsi/fsi-slave.h | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index e6ed2d0773b6..eb15e5f5a2ee 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -304,6 +304,7 @@ static int fsi_slave_handle_error(struct fsi_slave *slave, bool write,
 int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
 			void *val, size_t size)
 {
+	unsigned long flags;
 	uint8_t id = slave->id;
 	int rc, err_rc, i;
 
@@ -311,6 +312,7 @@ int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
 	if (rc)
 		return rc;
 
+	spin_lock_irqsave(&slave->lock, flags);
 	for (i = 0; i < slave_retries; i++) {
 		rc = fsi_master_read(slave->master, slave->link,
 				id, addr, val, size);
@@ -321,6 +323,7 @@ int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
 		if (err_rc)
 			break;
 	}
+	spin_unlock_irqrestore(&slave->lock, flags);
 
 	return rc;
 }
@@ -329,6 +332,7 @@ EXPORT_SYMBOL_GPL(fsi_slave_read);
 int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
 			const void *val, size_t size)
 {
+	unsigned long flags;
 	uint8_t id = slave->id;
 	int rc, err_rc, i;
 
@@ -336,6 +340,7 @@ int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
 	if (rc)
 		return rc;
 
+	spin_lock_irqsave(&slave->lock, flags);
 	for (i = 0; i < slave_retries; i++) {
 		rc = fsi_master_write(slave->master, slave->link,
 				id, addr, val, size);
@@ -346,6 +351,7 @@ int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
 		if (err_rc)
 			break;
 	}
+	spin_unlock_irqrestore(&slave->lock, flags);
 
 	return rc;
 }
@@ -1005,6 +1011,7 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 	if (!slave)
 		return -ENOMEM;
 
+	spin_lock_init(&slave->lock);
 	dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
 	slave->dev.type = &cfam_type;
 	slave->dev.parent = &master->dev;
diff --git a/drivers/fsi/fsi-slave.h b/drivers/fsi/fsi-slave.h
index 42af2fae0329..6f8fb97023fb 100644
--- a/drivers/fsi/fsi-slave.h
+++ b/drivers/fsi/fsi-slave.h
@@ -6,6 +6,7 @@
 
 #include <linux/cdev.h>
 #include <linux/device.h>
+#include <linux/spinlock.h>
 
 #define FSI_SLAVE_BASE			0x800
 
@@ -100,6 +101,7 @@ struct fsi_slave {
 	struct device		dev;
 	struct fsi_master	*master;
 	struct cdev		cdev;
+	spinlock_t		lock;	/* atomic access and error recovery */
 	int			cdev_idx;
 	int			id;	/* FSI address */
 	int			link;	/* FSI link# */
-- 
2.39.3