Re: [Patch v6 4/7] slimbus: Add support for 'clock-pause' feature

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Thanks for the review comments



On 07/10/17 09:06, Jonathan Neuschäfer wrote:
Hi, some trivial comments below.

On Fri, Oct 06, 2017 at 05:51:33PM +0200, srinivas.kandagatla@xxxxxxxxxx wrote:
From: Sagar Dharia <sdharia@xxxxxxxxxxxxxx>

Per slimbus specification, a reconfiguration sequence known as
'clock pause' needs to be broadcast over the bus while entering low-
power mode. Clock-pause is initiated by the controller driver.
To exit clock-pause, controller typically wakes up the framer device.
Since wakeup precedure is controller-specific, framework calls it via
controller's function pointer to invoke it.

Signed-off-by: Sagar Dharia <sdharia@xxxxxxxxxxxxxx>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
[...]
@@ -429,6 +444,14 @@ void slim_return_tx(struct slim_controller *ctrl, int err)
  		cur.cb(cur.ctx, err);
up(&ctrl->tx_sem);
+	if (!cur.clk_pause && (!cur.need_tid || err)) {
+		/**

This isn't really a kerneldoc comment.
Will fix all such instances in next version.

+		 * remove runtime-pm vote if this was TX only, or
+		 * if there was error during this transaction
+		 */
+		pm_runtime_mark_last_busy(ctrl->dev.parent);
+		pm_runtime_put_autosuspend(ctrl->dev.parent);
+	}
  }
  EXPORT_SYMBOL_GPL(slim_return_tx);
[...]
+/**
+ * slim_ctrl_clk_pause: Called by slimbus controller to enter/exit 'clock pause'
+ * Slimbus specification needs this sequence to turn-off clocks for the bus.
+ * The sequence involves sending 3 broadcast messages (reconfiguration
+ * sequence) to inform all devices on the bus.
+ * To exit clock-pause, controller typically wakes up active framer device.
+ * @ctrl: controller requesting bus to be paused or woken up
+ * @wakeup: Wakeup this controller from clock pause.
+ * @restart: Restart time value per spec used for clock pause. This value
+ *	isn't used when controller is to be woken up.
+ * This API executes clock pause reconfiguration sequence if wakeup is false.
+ * If wakeup is true, controller's wakeup is called.
+ * For entering clock-pause, -EBUSY is returned if a message txn in pending.
+ */
+int slim_ctrl_clk_pause(struct slim_controller *ctrl, bool wakeup, u8 restart)
+{
+	int i, ret = 0;
+	unsigned long flags;
+	struct slim_sched *sched = &ctrl->sched;
+	struct slim_val_inf msg = {0, 0, NULL, NULL, NULL, NULL};
+
+	DEFINE_SLIM_BCAST_TXN(txn, SLIM_MSG_MC_BEGIN_RECONFIGURATION,
+				3, SLIM_LA_MANAGER, &msg);
+
+	if (wakeup == false && restart > SLIM_CLK_UNSPECIFIED)
+		return -EINVAL;
+
+	mutex_lock(&sched->m_reconf);
+	if (wakeup) {
+		if (sched->clk_state == SLIM_CLK_ACTIVE) {
+			mutex_unlock(&sched->m_reconf);
+			return 0;
+		}
+
+		/**

ditto

+		 * Fine-tune calculation based on clock gear,
+		 * message-bandwidth after bandwidth management
+		 */
+		ret = wait_for_completion_timeout(&sched->pause_comp,
+				msecs_to_jiffies(100));
+		if (!ret) {
+			mutex_unlock(&sched->m_reconf);
+			pr_err("Previous clock pause did not finish");
+			return -ETIMEDOUT;
+		}
+		ret = 0;
+
+		/**

ditto

+		 * Slimbus framework will call controller wakeup
+		 * Controller should make sure that it sets active framer
+		 * out of clock pause
+		 */
+		if (sched->clk_state == SLIM_CLK_PAUSED && ctrl->wakeup)
+			ret = ctrl->wakeup(ctrl);
+		if (!ret)
+			sched->clk_state = SLIM_CLK_ACTIVE;
+		mutex_unlock(&sched->m_reconf);
+
+		return ret;
+	}
[...]


Thanks,
Jonathan Neuschäfer

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