msm: mdss: dp: add support for downstream device power management

Implement the necessary programming sequence to configure the
uPacket RX of a connected downstream device in power save mode.
Add a new sysfs node to trigger the configuration as follows:

To enter power save mode:
   * echo 1 > /sys/class/graphics/<fbi>/psm

To exit power save mode:
   * echo 0 > /sys/class/graphics/<fbi>/psm

where fbi is the framebuffer node corresponding to the display
port device.

CRs-Fixed: 1076516
Change-Id: I306ff4451d56dfa7edcff93fe26842ae9af71b69
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>

3 files changed, 187 insertions, 0 deletions

diff --git a/drivers/video/fbdev/msm/mdss_dp.c b/drivers/video/fbdev/msm/mdss_dp.c
index f81226b6fe15..cd7471b1cd8e 100644
--- a/drivers/video/fbdev/msm/mdss_dp.c
+++ b/drivers/video/fbdev/msm/mdss_dp.c
@@ -1235,6 +1235,15 @@ static int mdss_dp_on_irq(struct mdss_dp_drv_pdata *dp_drv)
 
 		dp_drv->power_on = true;
 
+		if (dp_drv->psm_enabled) {
+			ret = mdss_dp_aux_send_psm_request(dp_drv, false);
+			if (ret) {
+				pr_err("Failed to exit low power mode, rc=%d\n",
+					ret);
+				goto exit;
+			}
+		}
+
 		ret = mdss_dp_train_main_link(dp_drv);
 
 		mutex_unlock(&dp_drv->train_mutex);
@@ -1302,6 +1311,15 @@ int mdss_dp_on_hpd(struct mdss_dp_drv_pdata *dp_drv)
 
 	mdss_dp_configure_source_params(dp_drv, &ln_map);
 
+	if (dp_drv->psm_enabled) {
+		ret = mdss_dp_aux_send_psm_request(dp_drv, false);
+		if (ret) {
+			pr_err("Failed to exit low power mode, rc=%d\n", ret);
+			goto exit;
+		}
+	}
+
+
 link_training:
 	dp_drv->power_on = true;
 
@@ -1869,6 +1887,124 @@ static ssize_t mdss_dp_sysfs_rda_s3d_mode(struct device *dev,
 	return ret;
 }
 
+static bool mdss_dp_is_test_ongoing(struct mdss_dp_drv_pdata *dp)
+{
+	return dp->hpd_irq_clients_notified;
+}
+
+/**
+ * mdss_dp_psm_config() - Downstream device uPacket RX Power Management
+ * @dp: Display Port Driver data
+ *
+ * Perform required steps to configure the uPacket RX of a downstream
+ * connected device in a power-save mode.
+ */
+static int mdss_dp_psm_config(struct mdss_dp_drv_pdata *dp, bool enable)
+{
+	int ret = 0;
+
+	if (!dp) {
+		pr_err("invalid data\n");
+		return -EINVAL;
+	}
+
+	if (dp->psm_enabled == enable) {
+		pr_debug("No change in psm requested\n");
+		goto end;
+	}
+
+	pr_debug("Power save mode %s requested\n", enable ? "entry" : "exit");
+
+	if (enable) {
+		ret = mdss_dp_aux_send_psm_request(dp, true);
+		if (ret)
+			goto end;
+
+		/*
+		 * If this configuration is requested as part of an
+		 * automated test, then HPD notification has already been
+		 * sent out. Just disable the main-link and turn off DP Tx.
+		 *
+		 * Otherwise, trigger a complete shutdown of the pipeline.
+		 */
+		if (mdss_dp_is_test_ongoing(dp)) {
+			mdss_dp_mainlink_push_idle(&dp->panel_data);
+			mdss_dp_off_irq(dp);
+		} else {
+			mdss_dp_notify_clients(dp, false);
+		}
+	} else {
+		/*
+		 * If this configuration is requested as part of an
+		 * automated test, then just perform a link retraining.
+		 *
+		 * Otherwise, re-initialize the host and setup the complete
+		 * pipeline from scratch by sending a connection notification
+		 * to user modules.
+		 */
+		if (mdss_dp_is_test_ongoing(dp)) {
+			mdss_dp_link_retraining(dp);
+		} else {
+			mdss_dp_host_init(&dp->panel_data);
+			mdss_dp_notify_clients(dp, true);
+		}
+	}
+
+end:
+	pr_debug("Power save mode %s %s\n",
+		dp->psm_enabled ? "entry" : "exit",
+		ret ? "failed" : "successful");
+
+	return ret;
+}
+
+static ssize_t mdss_dp_wta_psm(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int psm;
+	int rc;
+	ssize_t ret = strnlen(buf, PAGE_SIZE);
+	struct mdss_dp_drv_pdata *dp = mdss_dp_get_drvdata(dev);
+
+	if (!dp) {
+		pr_err("invalid data\n");
+		ret = -EINVAL;
+		goto end;
+	}
+
+	rc = kstrtoint(buf, 10, &psm);
+	if (rc) {
+		pr_err("kstrtoint failed. ret=%d\n", (int)ret);
+		goto end;
+	}
+
+	rc = mdss_dp_psm_config(dp, psm ? true : false);
+	if (rc) {
+		pr_err("failed to config Power Save Mode\n");
+		goto end;
+	}
+
+end:
+	return ret;
+}
+
+static ssize_t mdss_dp_rda_psm(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	ssize_t ret;
+	struct mdss_dp_drv_pdata *dp = mdss_dp_get_drvdata(dev);
+
+	if (!dp) {
+		pr_err("invalid input\n");
+		return -EINVAL;
+	}
+
+	ret = snprintf(buf, PAGE_SIZE, "%d\n", dp->psm_enabled ? 1 : 0);
+	pr_debug("psm: %s\n", dp->psm_enabled ? "enabled" : "disabled");
+
+	return ret;
+}
+
 static ssize_t mdss_dp_wta_hpd(struct device *dev,
 	struct device_attribute *attr, const char *buf, size_t count)
 {
@@ -1927,11 +2063,15 @@ static DEVICE_ATTR(s3d_mode, S_IRUGO | S_IWUSR, mdss_dp_sysfs_rda_s3d_mode,
 	mdss_dp_sysfs_wta_s3d_mode);
 static DEVICE_ATTR(hpd, S_IRUGO | S_IWUSR, mdss_dp_rda_hpd,
 	mdss_dp_wta_hpd);
+static DEVICE_ATTR(psm, S_IRUGO | S_IWUSR, mdss_dp_rda_psm,
+	mdss_dp_wta_psm);
+
 
 static struct attribute *mdss_dp_fs_attrs[] = {
 	&dev_attr_connected.attr,
 	&dev_attr_s3d_mode.attr,
 	&dev_attr_hpd.attr,
+	&dev_attr_psm.attr,
 	NULL,
 };
 
diff --git a/drivers/video/fbdev/msm/mdss_dp.h b/drivers/video/fbdev/msm/mdss_dp.h
index 9b1fb7fc3dcd..5ab26b466765 100644
--- a/drivers/video/fbdev/msm/mdss_dp.h
+++ b/drivers/video/fbdev/msm/mdss_dp.h
@@ -401,6 +401,7 @@ struct mdss_dp_drv_pdata {
 	bool power_on;
 	bool sink_info_read;
 	bool hpd;
+	bool psm_enabled;
 
 	/* dp specific */
 	unsigned char *base;
@@ -683,6 +684,7 @@ void mdss_dp_lane_power_ctrl(struct mdss_dp_drv_pdata *ep, int up);
 void mdss_dp_config_ctrl(struct mdss_dp_drv_pdata *ep);
 char mdss_dp_gen_link_clk(struct mdss_panel_info *pinfo, char lane_cnt);
 int mdss_dp_aux_set_sink_power_state(struct mdss_dp_drv_pdata *ep, char state);
+int mdss_dp_aux_send_psm_request(struct mdss_dp_drv_pdata *dp, bool enable);
 void mdss_dp_aux_send_test_response(struct mdss_dp_drv_pdata *ep);
 void *mdss_dp_get_hdcp_data(struct device *dev);
 int mdss_dp_hdcp2p2_init(struct mdss_dp_drv_pdata *dp_drv);
diff --git a/drivers/video/fbdev/msm/mdss_dp_aux.c b/drivers/video/fbdev/msm/mdss_dp_aux.c
index efa343315a3c..fb88fb8fc335 100644
--- a/drivers/video/fbdev/msm/mdss_dp_aux.c
+++ b/drivers/video/fbdev/msm/mdss_dp_aux.c
@@ -1026,6 +1026,51 @@ int mdss_dp_aux_link_status_read(struct mdss_dp_drv_pdata *ep, int len)
 	return len;
 }
 
+/*
+ * mdss_dp_aux_send_psm_request() - sends a power save mode messge to sink
+ * @dp: Display Port Driver data
+ */
+int mdss_dp_aux_send_psm_request(struct mdss_dp_drv_pdata *dp, bool enable)
+{
+	u8 psm_request[4];
+	int rc = 0;
+
+	psm_request[0] = enable ? 2 : 1;
+
+	pr_debug("sending psm %s request\n", enable ? "entry" : "exit");
+	if (enable) {
+		dp_aux_write_buf(dp, 0x600, psm_request, 1, 0);
+	} else {
+		ktime_t timeout = ktime_add_ms(ktime_get(), 20);
+
+		/*
+		 * It could take up to 1ms (20 ms of embedded sinks) till
+		 * the sink is ready to reply to this AUX transaction. It is
+		 * expected that the source keep retrying periodically during
+		 * this time.
+		 */
+		for (;;) {
+			rc = dp_aux_write_buf(dp, 0x600, psm_request, 1, 0);
+			if ((rc >= 0) ||
+				(ktime_compare(ktime_get(), timeout) > 0))
+				break;
+			usleep_range(100, 120);
+		}
+
+		/*
+		 * if the aux transmission succeeded, then the function would
+		 * return the number of bytes transmitted.
+		 */
+		if (rc > 0)
+			rc = 0;
+	}
+
+	if (!rc)
+		dp->psm_enabled = enable;
+
+	return rc;
+}
+
 /**
  * mdss_dp_aux_send_test_response() - sends a test response to the sink
  * @dp: Display Port Driver data