HSI: omap_ssi_port: prepare start_tx/stop_tx for blocking pm_runtime calls

ssi_start_tx and ssi_stop_tx may be called from atomic context. Once
pm_runtime_irq_safe() is removed for omap-ssi, this will fail, due
to blocking pm_runtime_*_sync() calls.

This fixes ssi_stop_tx by using non-sync API and ssi_start_tx by
using a worker thread.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Tested-by: Pavel Machek <pavel@ucw.cz>

2 files changed, 20 insertions, 5 deletions

diff --git a/drivers/hsi/controllers/omap_ssi.h b/drivers/hsi/controllers/omap_ssi.h
index 6cdaad8805f7..5467f61e5086 100644
--- a/drivers/hsi/controllers/omap_ssi.h
+++ b/drivers/hsi/controllers/omap_ssi.h
@@ -79,6 +79,7 @@ struct omap_ssm_ctx {
  * @pio_tasklet: Bottom half for PIO transfers and events
  * @flags: flags to keep track of states
  * @wk_refcount: Reference count for output wake line
+ * @work: worker for starting TX
  * @sys_mpu_enable: Context for the interrupt enable register for irq 0
  * @sst: Context for the synchronous serial transmitter
  * @ssr: Context for the synchronous serial receiver
@@ -103,6 +104,7 @@ struct omap_ssi_port {
         bool                    wktest:1; /* FIXME: HACK to be removed */
         unsigned long           flags;
         unsigned int            wk_refcount;
+        struct work_struct      work;
         /* OMAP SSI port context */
         u32                     sys_mpu_enable; /* We use only one irq */
         struct omap_ssm_ctx     sst;
diff --git a/drivers/hsi/controllers/omap_ssi_port.c b/drivers/hsi/controllers/omap_ssi_port.c
index 0d3452393670..cc56d0ee82a2 100644
--- a/drivers/hsi/controllers/omap_ssi_port.c
+++ b/drivers/hsi/controllers/omap_ssi_port.c
@@ -567,12 +567,22 @@ static int ssi_flush(struct hsi_client *cl)
         return 0;
 }
 
+static void start_tx_work(struct work_struct *work)
+{
+        struct omap_ssi_port *omap_port =
+                                container_of(work, struct omap_ssi_port, work);
+        struct hsi_port *port = to_hsi_port(omap_port->dev);
+        struct hsi_controller *ssi = to_hsi_controller(port->device.parent);
+        struct omap_ssi_controller *omap_ssi = hsi_controller_drvdata(ssi);
+
+        pm_runtime_get_sync(omap_port->pdev); /* Grab clocks */
+        writel(SSI_WAKE(0), omap_ssi->sys + SSI_SET_WAKE_REG(port->num));
+}
+
 static int ssi_start_tx(struct hsi_client *cl)
 {
         struct hsi_port *port = hsi_get_port(cl);
         struct omap_ssi_port *omap_port = hsi_port_drvdata(port);
-        struct hsi_controller *ssi = to_hsi_controller(port->device.parent);
-        struct omap_ssi_controller *omap_ssi = hsi_controller_drvdata(ssi);
 
         dev_dbg(&port->device, "Wake out high %d\n", omap_port->wk_refcount);
 
@@ -581,10 +591,10 @@ static int ssi_start_tx(struct hsi_client *cl)
                 spin_unlock_bh(&omap_port->wk_lock);
                 return 0;
         }
-        pm_runtime_get_sync(omap_port->pdev); /* Grab clocks */
-        writel(SSI_WAKE(0), omap_ssi->sys + SSI_SET_WAKE_REG(port->num));
         spin_unlock_bh(&omap_port->wk_lock);
 
+        schedule_work(&omap_port->work);
+
         return 0;
 }
 
@@ -604,9 +614,10 @@ static int ssi_stop_tx(struct hsi_client *cl)
                 return 0;
         }
         writel(SSI_WAKE(0), omap_ssi->sys + SSI_CLEAR_WAKE_REG(port->num));
-        pm_runtime_put_sync(omap_port->pdev); /* Release clocks */
         spin_unlock_bh(&omap_port->wk_lock);
 
+        pm_runtime_put(omap_port->pdev); /* Release clocks */
+
         return 0;
 }
 
@@ -1149,6 +1160,8 @@ static int ssi_port_probe(struct platform_device *pd)
         omap_port->pdev = &pd->dev;
         omap_port->port_id = port_id;
 
+        INIT_WORK(&omap_port->work, start_tx_work);
+
         /* initialize HSI port */
         port->async     = ssi_async;
         port->setup     = ssi_setup;