[PATCH V2 6/6] slim: qcom: Add runtime-pm support using clock-pause feature

[Sagar Dharia]

Slimbus HW mandates that clock-pause sequence has to be executed
before disabling relevant interface and core clocks.
Runtime-PM's autosuspend feature is used here to enter/exit low
power mode for Qualcomm's Slimbus controller. Autosuspend feature
enables driver to avoid changing power-modes too frequently since
entering clock-pause is an expensive sequence

Signed-off-by: Sagar Dharia <sdharia@xxxxxxxxxxxxxx>
---
 drivers/slimbus/slim-qcom-ctrl.c | 133 ++++++++++++++++++++++++++++++++++++++-
 drivers/slimbus/slim-qcom.h      |   1 +
 2 files changed, 132 insertions(+), 2 deletions(-)

diff --git a/drivers/slimbus/slim-qcom-ctrl.c b/drivers/slimbus/slim-qcom-ctrl.c
index feae9d1..ec8687d 100644
--- a/drivers/slimbus/slim-qcom-ctrl.c
+++ b/drivers/slimbus/slim-qcom-ctrl.c
@@ -21,6 +21,7 @@
 #include <linux/clk.h>
 #include <linux/of.h>
 #include <linux/slimbus.h>
+#include <linux/pm_runtime.h>
 #include "slim-qcom.h"
 
 #define MSM_SLIM_NAME	"msm_slim_ctrl"
@@ -193,6 +194,7 @@ rx_ret_irq:
 		if (notify_rx)
 			complete(&dev->rx_msgq_notify);
 	}
+	pm_runtime_mark_last_busy(dev->dev);
 	return IRQ_HANDLED;
 }
 
@@ -211,6 +213,28 @@ static void msm_slim_wait_retry(struct msm_slim_ctrl *dev)
 	msleep(msec_per_frm);
 }
 
+static int msm_clk_pause_wakeup(struct slim_controller *ctrl)
+{
+	struct msm_slim_ctrl *dev = slim_get_ctrldata(ctrl);
+
+	clk_prepare_enable(dev->hclk);
+	clk_prepare_enable(dev->rclk);
+	writel_relaxed(1, dev->base + FRM_WAKEUP);
+	/* Make sure framer wakeup write goes through before ISR fires */
+	mb();
+	/**
+	 * HW Workaround: Currently, slave is reporting lost-sync messages
+	 * after slimbus comes out of clock pause.
+	 * Transaction with slave fail before slave reports that message
+	 * Give some time for that report to come
+	 * Slimbus wakes up in clock gear 10 at 24.576MHz. With each superframe
+	 * being 250 usecs, we wait for 5-10 superframes here to ensure
+	 * we get the message
+	 */
+	usleep_range(1250, 2500);
+	return 0;
+}
+
 static void msm_slim_cb(void *ctx, int err)
 {
 	if (err)
@@ -225,14 +249,29 @@ static int msm_xfer_msg(struct slim_controller *ctrl, struct slim_msg_txn *txn)
 	struct msm_slim_ctrl *dev = slim_get_ctrldata(ctrl);
 	u32 *pbuf;
 	u8 *puc;
-	int timeout;
+	int ret, timeout;
 	u8 la = txn->la;
+	enum slim_clk_state cur_clk_state = ctrl->sched.clk_state;
 	struct msm_wr_cb wr_cb = {msm_slim_cb, (void *)&done};
 
 	/* No support to send this dest-type of message */
 	if (txn->dt == SLIM_MSG_DEST_ENUMADDR)
 		return -EPROTONOSUPPORT;
 
+	if (cur_clk_state == SLIM_CLK_ENTERING_PAUSE) {
+		if (txn->mc != SLIM_MSG_MC_BEGIN_RECONFIGURATION &&
+		    txn->mc != SLIM_MSG_MC_RECONFIGURE_NOW &&
+		    txn->mc != SLIM_MSG_MC_NEXT_PAUSE_CLOCK)
+			return -EBUSY;
+	} else {
+		ret = pm_runtime_get_sync(dev->dev);
+		if (ret < 0) {
+			pm_runtime_set_suspended(dev->dev);
+			dev_err(dev->dev, "runtime-pm vote failed:%d\n", ret);
+			return ret;
+		}
+	}
+
 	/* HW expects length field to be excluded */
 	txn->rl--;
 
@@ -276,6 +315,8 @@ static int msm_xfer_msg(struct slim_controller *ctrl, struct slim_msg_txn *txn)
 			txn->mt);
 
 	mutex_unlock(&dev->txn_lock);
+	if (cur_clk_state != SLIM_CLK_ENTERING_PAUSE)
+		pm_runtime_put(dev->dev);
 	return timeout ? 0 : -ETIMEDOUT;
 }
 
@@ -295,6 +336,13 @@ static int msm_set_laddr(struct slim_controller *ctrl,
 	ea[2] = (u8) (ead->prod_code & 0xFF);
 	ea[1] = ead->dev_index;
 	ea[0] = ead->instance;
+
+	ret = pm_runtime_get_sync(dev->dev);
+	if (ret < 0) {
+		pm_runtime_set_suspended(dev->dev);
+		dev_err(dev->dev, "runtime-pm vote failed:%d\n", ret);
+		return ret;
+	}
 	mutex_lock(&dev->txn_lock);
 	/**
 	 * Retries are needed since bus may lose sync when multiple devices
@@ -305,6 +353,7 @@ retry_laddr:
 	buf = (u32 *)msm_slim_get_tx(dev, &wr_cb);
 	if (buf == NULL) {
 		mutex_unlock(&dev->txn_lock);
+		pm_runtime_put(dev->dev);
 		return -ENOMEM;
 	}
 
@@ -332,6 +381,7 @@ retry_laddr:
 		}
 	}
 	mutex_unlock(&dev->txn_lock);
+	pm_runtime_put(dev->dev);
 	return ret;
 }
 
@@ -512,6 +562,7 @@ static int msm_slim_probe(struct platform_device *pdev)
 	}
 	dev->ctrl.set_laddr = msm_set_laddr;
 	dev->ctrl.xfer_msg = msm_xfer_msg;
+	dev->ctrl.wakeup =  msm_clk_pause_wakeup;
 
 	mutex_init(&dev->txn_lock);
 	init_completion(&dev->rx_msgq_notify);
@@ -615,6 +666,12 @@ static int msm_slim_probe(struct platform_device *pdev)
 	/* Add devices registered with board-info now that controller is up */
 	slim_ctrl_add_boarddevs(&dev->ctrl);
 
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_autosuspend_delay(&pdev->dev, MSM_SLIM_AUTOSUSPEND);
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_mark_last_busy(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
 	dev_dbg(dev->dev, "MSM SB controller is up:ver:0x%x!\n", dev->ver);
 	return 0;
 
@@ -651,6 +708,7 @@ static int msm_slim_remove(struct platform_device *pdev)
 	struct resource *slim_mem;
 	struct resource *slew_mem = dev->slew_mem;
 
+	pm_runtime_disable(&pdev->dev);
 	free_irq(dev->irq, dev);
 	slim_del_controller(&dev->ctrl);
 	clk_put(dev->rclk);
@@ -671,20 +729,91 @@ static int msm_slim_remove(struct platform_device *pdev)
 	return 0;
 }
 
+/**
+ * If PM_RUNTIME is not defined, these 2 functions become helper
+ * functions to be called from system suspend/resume.
+ */
+#ifdef CONFIG_PM
+static int msm_slim_runtime_suspend(struct device *device)
+{
+	struct platform_device *pdev = to_platform_device(device);
+	struct msm_slim_ctrl *dev = platform_get_drvdata(pdev);
+	int ret;
+
+	dev_dbg(device, "pm_runtime: suspending...\n");
+	ret = slim_ctrl_clk_pause(&dev->ctrl, false, SLIM_CLK_UNSPECIFIED);
+	if (ret)
+		dev_err(device, "clk pause not entered:%d", ret);
+	else {
+		clk_disable_unprepare(dev->hclk);
+		clk_disable_unprepare(dev->rclk);
+	}
+	return ret;
+}
+
+static int msm_slim_runtime_resume(struct device *device)
+{
+	struct platform_device *pdev = to_platform_device(device);
+	struct msm_slim_ctrl *dev = platform_get_drvdata(pdev);
+	int ret = 0;
+
+	dev_dbg(device, "pm_runtime: resuming...\n");
+	ret = slim_ctrl_clk_pause(&dev->ctrl, true, 0);
+	if (ret)
+		dev_err(device, "clk pause not exited:%d", ret);
+	return ret;
+}
+#endif
+
 #ifdef CONFIG_PM_SLEEP
 static int msm_slim_suspend(struct device *dev)
 {
-	return 0;
+	int ret = 0;
+
+	if (!pm_runtime_enabled(dev) ||
+		(!pm_runtime_suspended(dev))) {
+		dev_dbg(dev, "system suspend");
+		ret = msm_slim_runtime_suspend(dev);
+	}
+	if (ret == -EISCONN) {
+		/**
+		* If the clock pause failed due to active channels, there is
+		* a possibility that some audio stream is active during suspend
+		* We dont want to return suspend failure in that case so that
+		* display and relevant components can still go to suspend.
+		* If there is some other error, then it should prevent
+		* system level suspend
+		*/
+		ret = 0;
+	}
+	return ret;
 }
 
 static int msm_slim_resume(struct device *dev)
 {
+	if (!pm_runtime_enabled(dev) || !pm_runtime_suspended(dev)) {
+		int ret;
+
+		dev_dbg(dev, "system resume");
+		ret = msm_slim_runtime_resume(dev);
+		if (!ret) {
+			pm_runtime_mark_last_busy(dev);
+			pm_request_autosuspend(dev);
+		}
+		return ret;
+
+	}
 	return 0;
 }
 #endif /* CONFIG_PM_SLEEP */
 
 static const struct dev_pm_ops msm_slim_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(msm_slim_suspend, msm_slim_resume)
+	SET_RUNTIME_PM_OPS(
+			   msm_slim_runtime_suspend,
+			   msm_slim_runtime_resume,
+			   NULL
+	)
 };
 
 static const struct of_device_id msm_slim_dt_match[] = {
diff --git a/drivers/slimbus/slim-qcom.h b/drivers/slimbus/slim-qcom.h
index 32073fc..f37a10a 100644
--- a/drivers/slimbus/slim-qcom.h
+++ b/drivers/slimbus/slim-qcom.h
@@ -25,6 +25,7 @@
 #define SLIM_ROOT_FREQ 24576000
 #define INIT_MX_RETRIES 10
 #define DEF_RETRY_MS	10
+#define MSM_SLIM_AUTOSUSPEND 1000
 
 /* MAX message size over control channel */
 #define SLIM_MSGQ_BUF_LEN	40
-- 
1.8.2.1

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