[PATCH linux dev-5.4 v2] fsi: core: Set slave local bus ownership during init

[Eddie James]

The FSI specification indicates that a slave will prevent access to the
CFAM address space for a master without local bus ownership. Therefore,
force local bus ownership when initializing the slave.

Signed-off-by: Eddie James <eajames at linux.ibm.com>
---
 drivers/fsi/fsi-core.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 8244da8a7241..358128b037e2 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -50,6 +50,7 @@ static const int engine_page_size = 0x400;
 #define FSI_SMODE		0x0	/* R/W: Mode register */
 #define FSI_SISC		0x8	/* R/W: Interrupt condition */
 #define FSI_SSTAT		0x14	/* R  : Slave status */
+#define FSI_SLBUS		0x30	/* W  : LBUS Ownership */
 #define FSI_LLMODE		0x100	/* R/W: Link layer mode register */
 
 /*
@@ -66,6 +67,11 @@ static const int engine_page_size = 0x400;
 #define FSI_SMODE_LBCRR_SHIFT	8		/* Clk ratio shift */
 #define FSI_SMODE_LBCRR_MASK	0xf		/* Clk ratio mask */
 
+/*
+ * SLBUS fields
+ */
+#define FSI_SLBUS_FORCE		0x80000000	/* Force LBUS ownership */
+
 /*
  * LLMODE fields
  */
@@ -981,7 +987,7 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 	uint32_t cfam_id;
 	struct fsi_slave *slave;
 	uint8_t crc;
-	__be32 data, llmode;
+	__be32 data, llmode, slbus;
 	int rc;
 
 	/* Currently, we only support single slaves on a link, and use the
@@ -1052,6 +1058,20 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 
 	}
 
+	/*
+	 * The FSI specification requires that the master claim ownership of
+	 * bus before accessing the CFAM address space. This driver doesn't yet
+	 * support more complex multi-master situations, so just force
+	 * ownership of the bus now.
+	 */
+	slbus = cpu_to_be32(FSI_SLBUS_FORCE);
+	rc = fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SLBUS,
+			      &slbus, sizeof(slbus));
+	if (rc)
+		dev_warn(&master->dev,
+			 "can't set slbus on slave:%02x:%02x %d\n", link, id,
+			 rc);
+
 	rc = fsi_slave_set_smode(slave);
 	if (rc) {
 		dev_warn(&master->dev,
-- 
2.24.0