[PATCH v4 23/23] drivers/fsi: Use asynchronous slave mode

[Christopher Bostic]

From: Jeremy Kerr <j...@ozlabs.org>

For slaves that are behind a software-clocked master, we want FSI CFAMs
to run asynchronously to the FSI clock, so set up our slaves to be in
async mode.

Signed-off-by: Jeremy Kerr <j...@ozlabs.org>
Signed-off-by: Chris Bostic <cbos...@linux.vnet.ibm.com>
---
 drivers/fsi/fsi-core.c        | 22 +++++++++++++++++++++-
 drivers/fsi/fsi-master-gpio.c |  1 +
 drivers/fsi/fsi-master.h      |  2 ++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 747d0e3..a6ed34f 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -47,6 +47,7 @@
 #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_LLMODE             0x100   /* R/W: Link layer mode register */
 
 /*
  * SMODE fields
@@ -62,6 +63,11 @@
 #define FSI_SMODE_LBCRR_SHIFT  8               /* Clk ratio shift */
 #define FSI_SMODE_LBCRR_MASK   0xf             /* Clk ratio mask */
 
+/*
+ * LLMODE fields
+ */
+#define FSI_LLMODE_ASYNC       0x1
+
 #define FSI_SLAVE_SIZE_23b             0x800000
 
 static DEFINE_IDA(master_ida);
@@ -560,8 +566,8 @@ static void fsi_slave_release(struct device *dev)
 
 static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 {
+       uint32_t chip_id, llmode;
        struct fsi_slave *slave;
-       uint32_t chip_id;
        uint8_t crc;
        int rc;
 
@@ -597,6 +603,20 @@ static int fsi_slave_init(struct fsi_master *master, int 
link, uint8_t id)
                return -ENODEV;
        }
 
+       /* If we're behind a master that doesn't provide a self-running bus
+        * clock, put the slave into async mode
+        */
+       if (master->flags & FSI_MASTER_FLAG_SWCLOCK) {
+               llmode = cpu_to_be32(FSI_LLMODE_ASYNC);
+               rc = fsi_master_write(master, link, id,
+                               FSI_SLAVE_BASE + FSI_LLMODE,
+                               &llmode, sizeof(llmode));
+               if (rc)
+                       dev_warn(&master->dev,
+                               "can't set llmode on slave:%02x:%02x %d\n",
+                               link, id, rc);
+       }
+
        /* We can communicate with a slave; create the slave device and
         * register.
         */
diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
index 84d5595..f3fcede 100644
--- a/drivers/fsi/fsi-master-gpio.c
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -573,6 +573,7 @@ static int fsi_master_gpio_probe(struct platform_device 
*pdev)
        master->gpio_mux = gpio;
 
        master->master.n_links = 1;
+       master->master.flags = FSI_MASTER_FLAG_SWCLOCK;
        master->master.read = fsi_master_gpio_read;
        master->master.write = fsi_master_gpio_write;
        master->master.term = fsi_master_gpio_term;
diff --git a/drivers/fsi/fsi-master.h b/drivers/fsi/fsi-master.h
index d6a4885..fd39924 100644
--- a/drivers/fsi/fsi-master.h
+++ b/drivers/fsi/fsi-master.h
@@ -19,6 +19,8 @@
 
 #include <linux/device.h>
 
+#define FSI_MASTER_FLAG_SWCLOCK        0x1
+
 struct fsi_master {
        struct device   dev;
        int             idx;
-- 
1.8.2.2