HSI: omap-ssi: add clk change support

This adds support for frequency changes of the SSI
functional clock, which may occur due to DVFS.

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

3 files changed, 89 insertions, 0 deletions

diff --git a/drivers/hsi/controllers/omap_ssi.h b/drivers/hsi/controllers/omap_ssi.h
index e493321cb0c3..7b4dec2c69ff 100644
--- a/drivers/hsi/controllers/omap_ssi.h
+++ b/drivers/hsi/controllers/omap_ssi.h
@@ -134,6 +134,8 @@ struct gdd_trn {
  * @gdd_tasklet: bottom half for DMA transfers
  * @gdd_trn: Array of GDD transaction data for ongoing GDD transfers
  * @lock: lock to serialize access to GDD
+ * @fck_nb: DVFS notfifier block
+ * @fck_rate: clock rate
  * @loss_count: To follow if we need to restore context or not
  * @max_speed: Maximum TX speed (Kb/s) set by the clients.
  * @sysconfig: SSI controller saved context
@@ -151,6 +153,7 @@ struct omap_ssi_controller {
         struct tasklet_struct   gdd_tasklet;
         struct gdd_trn          gdd_trn[SSI_MAX_GDD_LCH];
         spinlock_t              lock;
+        struct notifier_block   fck_nb;
         unsigned long           fck_rate;
         u32                     loss_count;
         u32                     max_speed;
@@ -164,6 +167,9 @@ struct omap_ssi_controller {
 #endif
 };
 
+void omap_ssi_port_update_fclk(struct hsi_controller *ssi,
+                               struct omap_ssi_port *omap_port);
+
 extern struct platform_driver ssi_port_pdriver;
 
 #endif /* __LINUX_HSI_OMAP_SSI_H__ */
diff --git a/drivers/hsi/controllers/omap_ssi_core.c b/drivers/hsi/controllers/omap_ssi_core.c
index 535c76038288..15b2a600d77b 100644
--- a/drivers/hsi/controllers/omap_ssi_core.c
+++ b/drivers/hsi/controllers/omap_ssi_core.c
@@ -290,6 +290,64 @@ static unsigned long ssi_get_clk_rate(struct hsi_controller *ssi)
         return rate;
 }
 
+static int ssi_clk_event(struct notifier_block *nb, unsigned long event,
+                                                                void *data)
+{
+        struct omap_ssi_controller *omap_ssi = container_of(nb,
+                                        struct omap_ssi_controller, fck_nb);
+        struct hsi_controller *ssi = to_hsi_controller(omap_ssi->dev);
+        struct clk_notifier_data *clk_data = data;
+        struct omap_ssi_port *omap_port;
+        int i;
+
+        switch (event) {
+        case PRE_RATE_CHANGE:
+                dev_dbg(&ssi->device, "pre rate change\n");
+
+                for (i = 0; i < ssi->num_ports; i++) {
+                        omap_port = omap_ssi->port[i];
+
+                        if (!omap_port)
+                                continue;
+
+                        /* Workaround for SWBREAK + CAwake down race in CMT */
+                        tasklet_disable(&omap_port->wake_tasklet);
+
+                        /* stop all ssi communication */
+                        pinctrl_pm_select_idle_state(omap_port->pdev);
+                        udelay(1); /* wait for racing frames */
+                }
+
+                break;
+        case ABORT_RATE_CHANGE:
+                dev_dbg(&ssi->device, "abort rate change\n");
+                /* Fall through */
+        case POST_RATE_CHANGE:
+                dev_dbg(&ssi->device, "post rate change (%lu -> %lu)\n",
+                        clk_data->old_rate, clk_data->new_rate);
+                omap_ssi->fck_rate = DIV_ROUND_CLOSEST(clk_data->new_rate, 1000); /* KHz */
+
+                for (i = 0; i < ssi->num_ports; i++) {
+                        omap_port = omap_ssi->port[i];
+
+                        if (!omap_port)
+                                continue;
+
+                        omap_ssi_port_update_fclk(ssi, omap_port);
+
+                        /* resume ssi communication */
+                        pinctrl_pm_select_default_state(omap_port->pdev);
+                        tasklet_enable(&omap_port->wake_tasklet);
+                }
+
+                break;
+        default:
+                break;
+        }
+
+        return NOTIFY_DONE;
+}
+
 static int ssi_get_iomem(struct platform_device *pd,
                 const char *name, void __iomem **pbase, dma_addr_t *phy)
 {
@@ -369,6 +427,10 @@ static int ssi_add_controller(struct hsi_controller *ssi,
                 goto out_err;
         }
 
+        omap_ssi->fck_nb.notifier_call = ssi_clk_event;
+        omap_ssi->fck_nb.priority = INT_MAX;
+        clk_notifier_register(omap_ssi->fck, &omap_ssi->fck_nb);
+
         /* TODO: find register, which can be used to detect context loss */
         omap_ssi->get_loss = NULL;
 
@@ -432,6 +494,7 @@ static void ssi_remove_controller(struct hsi_controller *ssi)
         int id = ssi->id;
         tasklet_kill(&omap_ssi->gdd_tasklet);
         hsi_unregister_controller(ssi);
+        clk_notifier_unregister(omap_ssi->fck, &omap_ssi->fck_nb);
         ida_simple_remove(&platform_omap_ssi_ida, id);
 }
 
diff --git a/drivers/hsi/controllers/omap_ssi_port.c b/drivers/hsi/controllers/omap_ssi_port.c
index 1569bbb53ee8..98b22e88085c 100644
--- a/drivers/hsi/controllers/omap_ssi_port.c
+++ b/drivers/hsi/controllers/omap_ssi_port.c
@@ -23,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
 #include <linux/pm_runtime.h>
+#include <linux/delay.h>
 
 #include <linux/gpio/consumer.h>
 #include <linux/debugfs.h>
@@ -514,6 +515,11 @@ static int ssi_flush(struct hsi_client *cl)
 
         pm_runtime_get_sync(omap_port->pdev);
         spin_lock_bh(&omap_port->lock);
+
+        /* stop all ssi communication */
+        pinctrl_pm_select_idle_state(omap_port->pdev);
+        udelay(1); /* wait for racing frames */
+
         /* Stop all DMA transfers */
         for (i = 0; i < SSI_MAX_GDD_LCH; i++) {
                 msg = omap_ssi->gdd_trn[i].msg;
@@ -550,6 +556,10 @@ static int ssi_flush(struct hsi_client *cl)
                 ssi_flush_queue(&omap_port->rxqueue[i], NULL);
         }
         ssi_flush_queue(&omap_port->brkqueue, NULL);
+
+        /* Resume SSI communication */
+        pinctrl_pm_select_default_state(omap_port->pdev);
+
         spin_unlock_bh(&omap_port->lock);
         pm_runtime_put_sync(omap_port->pdev);
 
@@ -1302,6 +1312,16 @@ static int ssi_restore_divisor(struct omap_ssi_port *omap_port)
         return 0;
 }
 
+void omap_ssi_port_update_fclk(struct hsi_controller *ssi,
+                               struct omap_ssi_port *omap_port)
+{
+        /* update divisor */
+        u32 div = ssi_calculate_div(ssi);
+        omap_port->sst.divisor = div;
+        ssi_restore_divisor(omap_port);
+}
+EXPORT_SYMBOL_GPL(omap_ssi_port_update_fclk);
+
 static int omap_ssi_port_runtime_suspend(struct device *dev)
 {
         struct hsi_port *port = dev_get_drvdata(dev);