fsi: Prevent multiple concurrent rescans

The bus scanning process isn't terribly good at parallel attempts
at rescanning the same bus. Let's have a per-master mutex protecting
the scanning process.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index dea5bd4..2c31563 100644 (file)
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -1203,8 +1203,14 @@ static void fsi_master_unscan(struct fsi_master *master)
 
 int fsi_master_rescan(struct fsi_master *master)
 {
+       int rc;
+
+       mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
-       return fsi_master_scan(master);
+       rc = fsi_master_scan(master);
+       mutex_unlock(&master->scan_lock);
+
+       return rc;
 }
 EXPORT_SYMBOL_GPL(fsi_master_rescan);
 
@@ -1240,6 +1246,7 @@ int fsi_master_register(struct fsi_master *master)
        int rc;
        struct device_node *np;
 
+       mutex_init(&master->scan_lock);
        master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL);
        dev_set_name(&master->dev, "fsi%d", master->idx);
 
@@ -1264,8 +1271,11 @@ int fsi_master_register(struct fsi_master *master)
        }
 
        np = dev_of_node(&master->dev);
-       if (!of_property_read_bool(np, "no-scan-on-init"))
+       if (!of_property_read_bool(np, "no-scan-on-init")) {
+               mutex_lock(&master->scan_lock);
                fsi_master_scan(master);
+               mutex_unlock(&master->scan_lock);
+       }
 
        return 0;
 }
@@ -1278,7 +1288,9 @@ void fsi_master_unregister(struct fsi_master *master)
                master->idx = -1;
        }
 
+       mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
+       mutex_unlock(&master->scan_lock);
        device_unregister(&master->dev);
 }
 EXPORT_SYMBOL_GPL(fsi_master_unregister);

diff --git a/drivers/fsi/fsi-master.h b/drivers/fsi/fsi-master.h
index f653f75..040a7d4 100644 (file)
--- a/drivers/fsi/fsi-master.h
+++ b/drivers/fsi/fsi-master.h
@@ -18,6 +18,7 @@
 #define DRIVERS_FSI_MASTER_H
 
 #include <linux/device.h>
+#include <linux/mutex.h>
 
 /* Various protocol delays */
 #define        FSI_ECHO_DELAY_CLOCKS   16      /* Number clocks for echo delay */
@@ -59,6 +60,7 @@ struct fsi_master {
        int             idx;
        int             n_links;
        int             flags;
+       struct mutex    scan_lock;
        int             (*read)(struct fsi_master *, int link, uint8_t id,
                                uint32_t addr, void *val, size_t size);
        int             (*write)(struct fsi_master *, int link, uint8_t id,