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Subject[PATCH 2/2] HSI: omap-ssi: add clk change support
Date
This adds support for frequency changes of the SSI
functional clock, which may occur due to DVFS.

Signed-off-By: Sebastian Reichel <sre@kernel.org>
---
drivers/hsi/controllers/omap_ssi.c | 63 +++++++++++++++++++++++++++++++++
drivers/hsi/controllers/omap_ssi.h | 6 ++++
drivers/hsi/controllers/omap_ssi_port.c | 20 +++++++++++
3 files changed, 89 insertions(+)

diff --git a/drivers/hsi/controllers/omap_ssi.c b/drivers/hsi/controllers/omap_ssi.c
index f6d3100b7a32..8bc5f2fed869 100644
--- a/drivers/hsi/controllers/omap_ssi.c
+++ b/drivers/hsi/controllers/omap_ssi.c
@@ -291,6 +291,64 @@ 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 __init ssi_get_iomem(struct platform_device *pd,
const char *name, void __iomem **pbase, dma_addr_t *phy)
{
@@ -371,6 +429,10 @@ static int __init 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;

@@ -434,6 +496,7 @@ 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.h b/drivers/hsi/controllers/omap_ssi.h
index f9aaf37262be..2797ab284460 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;
@@ -164,4 +167,7 @@ struct omap_ssi_controller {
#endif
};

+void omap_ssi_port_update_fclk(struct hsi_controller *ssi,
+ struct omap_ssi_port *omap_port);
+
#endif /* __LINUX_HSI_OMAP_SSI_H__ */
diff --git a/drivers/hsi/controllers/omap_ssi_port.c b/drivers/hsi/controllers/omap_ssi_port.c
index 02e66032ae73..6557aaa52a36 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/of_gpio.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);

@@ -1319,6 +1329,16 @@ 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);
--
2.7.0.rc3
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