[PATCH v3 2/6] firmware: ti_sci: Partial-IO support

[Markus Schneider-Pargmann]

Add support for Partial-IO poweroff. In Partial-IO pins of a few
hardware units can generate system wakeups while DDR memory is not
powered resulting in a fresh boot of the system. These hardware units in
the SoC are always powered so that some logic can detect pin activity.

If the system supports Partial-IO as described in the fw capabilities, a
sys_off handler is added. This sys_off handler decides if the poweroff
is executed by entering normal poweroff or Partial-IO instead. The
decision is made by checking if wakeup is enabled on all devices that
may wake up the SoC from Partial-IO.

The possible wakeup devices are found by checking which devices are
powered by the regulator supplying the "vddshv_canuart" line. These are
considered possible wakeup sources. Only wakeup sources that are
actually enabled by the user will be considered as a an active wakeup
source. If none of the wakeup sources are enabled the system will do a
normal poweroff. If at least one wakeup source is enabled it will
instead send a TI_SCI_MSG_PREPARE_SLEEP message from the sys_off
handler. Sending this message will result in an immediate shutdown of
the system. No execution is expected after this point. The code will
wait for 5s and do an emergency_restart afterwards if Partial-IO wasn't
entered at that point.

A short documentation about Partial-IO can be found in section 6.2.4.5
of the TRM at
  https://www.ti.com/lit/pdf/spruiv7

Signed-off-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
---
 drivers/firmware/ti_sci.c | 130 +++++++++++++++++++++++++++++++++++++++++++++-
 drivers/firmware/ti_sci.h |   5 ++
 2 files changed, 134 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
index 9ef86ea27a3c9ac6b9aa4a838a4f5e9fc09a81a9..fe964e5e2b2a06ba2fb9754537d28661951a6b78 100644
--- a/drivers/firmware/ti_sci.c
+++ b/drivers/firmware/ti_sci.c
@@ -3746,6 +3746,115 @@ static const struct dev_pm_ops ti_sci_pm_ops = {
 #endif
 };
 
+/*
+ * Enter Partial-IO, which disables everything including DDR with only a small
+ * logic being active for wakeup.
+ */
+static int tisci_enter_partial_io(struct ti_sci_info *info)
+{
+	struct ti_sci_msg_req_prepare_sleep *req;
+	struct ti_sci_xfer *xfer;
+	struct device *dev = info->dev;
+	int ret = 0;
+
+	xfer = ti_sci_get_one_xfer(info, TI_SCI_MSG_PREPARE_SLEEP,
+				   TI_SCI_FLAG_REQ_GENERIC_NORESPONSE,
+				   sizeof(*req), sizeof(struct ti_sci_msg_hdr));
+	if (IS_ERR(xfer)) {
+		ret = PTR_ERR(xfer);
+		dev_err(dev, "Message alloc failed(%d)\n", ret);
+		return ret;
+	}
+
+	req = (struct ti_sci_msg_req_prepare_sleep *)xfer->xfer_buf;
+	req->mode = TISCI_MSG_VALUE_SLEEP_MODE_PARTIAL_IO;
+	req->ctx_lo = 0;
+	req->ctx_hi = 0;
+	req->debug_flags = 0;
+
+	dev_info(dev, "Entering Partial-IO because a powered wakeup-enabled device was found.\n");
+
+	ret = ti_sci_do_xfer(info, xfer);
+	if (ret) {
+		dev_err(dev, "Mbox send fail %d\n", ret);
+		goto fail;
+	}
+
+fail:
+	ti_sci_put_one_xfer(&info->minfo, xfer);
+
+	return ret;
+}
+
+static bool tisci_canuart_wakeup_enabled(struct ti_sci_info *info)
+{
+	static const char canuart_name[] = "vddshv_canuart";
+	struct device_node *wakeup_node = NULL;
+
+	for (wakeup_node = of_find_node_with_property(NULL, "vio-supply");
+	     wakeup_node;
+	     wakeup_node = of_find_node_with_property(wakeup_node, "vio-supply")) {
+		struct device_node *supply_node;
+		const char *supply_name;
+		struct platform_device *pdev;
+		int ret;
+
+		supply_node = of_parse_phandle(wakeup_node, "vio-supply", 0);
+		if (!supply_node)
+			continue;
+
+		ret = of_property_read_string(supply_node, "regulator-name", &supply_name);
+		of_node_put(supply_node);
+		if (ret) {
+			dev_warn(info->dev, "Failed to parse vio-supply phandle at %pOF %d\n",
+				 wakeup_node, ret);
+			continue;
+		}
+
+		if (strncmp(canuart_name, supply_name, strlen(canuart_name)))
+			continue;
+
+		pdev = of_find_device_by_node(wakeup_node);
+		if (!pdev)
+			continue;
+
+		if (device_may_wakeup(&pdev->dev)) {
+			dev_dbg(info->dev, "%pOF identified as wakeup source for Partial-IO\n",
+				wakeup_node);
+			put_device(&pdev->dev);
+			of_node_put(wakeup_node);
+			return true;
+		}
+		put_device(&pdev->dev);
+	}
+
+	return false;
+}
+
+static int tisci_sys_off_handler(struct sys_off_data *data)
+{
+	struct ti_sci_info *info = data->cb_data;
+	bool enter_partial_io = tisci_canuart_wakeup_enabled(info);
+	int ret;
+
+	if (!enter_partial_io)
+		return NOTIFY_DONE;
+
+	ret = tisci_enter_partial_io(info);
+
+	if (ret) {
+		dev_err(info->dev,
+			"Failed to enter Partial-IO %pe, trying to do an emergency restart\n",
+			ERR_PTR(ret));
+		emergency_restart();
+	}
+
+	mdelay(5000);
+	emergency_restart();
+
+	return NOTIFY_DONE;
+}
+
 /* Description for K2G */
 static const struct ti_sci_desc ti_sci_pmmc_k2g_desc = {
 	.default_host_id = 2,
@@ -3889,6 +3998,19 @@ static int ti_sci_probe(struct platform_device *pdev)
 		goto out;
 	}
 
+	if (info->fw_caps & MSG_FLAG_CAPS_LPM_PARTIAL_IO) {
+		ret = devm_register_sys_off_handler(dev,
+						    SYS_OFF_MODE_POWER_OFF,
+						    SYS_OFF_PRIO_FIRMWARE,
+						    tisci_sys_off_handler,
+						    info);
+		if (ret) {
+			dev_err(dev, "Failed to register sys_off_handler %pe\n",
+				ERR_PTR(ret));
+			goto out;
+		}
+	}
+
 	dev_info(dev, "ABI: %d.%d (firmware rev 0x%04x '%s')\n",
 		 info->handle.version.abi_major, info->handle.version.abi_minor,
 		 info->handle.version.firmware_revision,
@@ -3898,7 +4020,13 @@ static int ti_sci_probe(struct platform_device *pdev)
 	list_add_tail(&info->node, &ti_sci_list);
 	mutex_unlock(&ti_sci_list_mutex);
 
-	return of_platform_populate(dev->of_node, NULL, NULL, dev);
+	ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
+	if (ret) {
+		dev_err(dev, "platform_populate failed %pe\n", ERR_PTR(ret));
+		goto out;
+	}
+	return 0;
+
 out:
 	if (!IS_ERR(info->chan_tx))
 		mbox_free_channel(info->chan_tx);
diff --git a/drivers/firmware/ti_sci.h b/drivers/firmware/ti_sci.h
index 053387d7baa064498e6a208daa7f70040ef87281..dec9e20cbe5da8f6d9393d56bb9a1e73cb083a42 100644
--- a/drivers/firmware/ti_sci.h
+++ b/drivers/firmware/ti_sci.h
@@ -592,6 +592,11 @@ struct ti_sci_msg_resp_get_clock_freq {
 struct ti_sci_msg_req_prepare_sleep {
 	struct ti_sci_msg_hdr	hdr;
 
+/*
+ * When sending perpare_sleep with MODE_PARTIAL_IO no response will be sent,
+ * no further steps are required.
+ */
+#define TISCI_MSG_VALUE_SLEEP_MODE_PARTIAL_IO				0x03
 #define TISCI_MSG_VALUE_SLEEP_MODE_DM_MANAGED				0xfd
 	u8			mode;
 	u32			ctx_lo;

-- 
2.45.2