[U-Boot] [PATCH 1/2] usb: xhci: implement FEAT_POWER hook for switching regulators for ports

[Philipp Tomsich]

When the FEAT_POWER flag is set/cleared for a port, power to this port
should be enabled/disabled.  As many embedded xHCI controllers do not
expose a signal to control this, extra effort may be required.

In order to link up setting/clearing FEAT_POWER with the regulator
framework (so either a regulator or a GPIO modelled as a fixed
regulator) can be switched, two callbacks are implemented in this
change: if regulators are available an optional property
'xhci,port-power' can contain a stringlist with names of regulators
that should be switched to control the power of ports (each entry in
the stringlist corresponds to its respective regulator).

For some versions of the RK3399-Q7 (at least revisions v1.1 and v1.2
are affected), we need to turn on the power for the port connected to
the on-module USB hub only when FEAT_POWER is set to ensure that the
hub does not enter a low-power mode that U-Boot's USB stack can't deal
with.  Note that Linux eventually manages to attach the hub even when
it's in its low-power state after a few seconds.

Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
---

 drivers/usb/host/xhci.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 4673738..dabba18 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -30,6 +30,7 @@
 #include <asm/unaligned.h>
 #include <linux/errno.h>
 #include "xhci.h"
+#include <power/regulator.h>
 
 #ifndef CONFIG_USB_MAX_CONTROLLER_COUNT
 #define CONFIG_USB_MAX_CONTROLLER_COUNT 1
@@ -872,6 +873,58 @@ static u32 xhci_port_state_to_neutral(u32 state)
 }
 
 /**
+ * Switch power at an external regulator each port at the root hub, when
+ * the FEAT_POWER feature is set/cleared.
+ *
+ * @param ctrl pointer to the xHCI controller
+ * @param req_index port number as in the control message (one-based)
+ * @param enable boolean indicating whether to enable or disable power
+ * @return returns 0 on success, an error-code on failure
+ */
+static int xhci_board_port_powerset(struct xhci_ctrl *ctrl, int req_index,
+				    bool enable)
+{
+#if CONFIG_IS_ENABLED(OF_CONTROL) && CONFIG_IS_ENABLED(DM_REGULATOR)
+	/* We start counting ports at 0, while the request counts from 1. */
+	int index = req_index - 1;
+	struct udevice *dev = ctrl->dev;
+	const char *regname = NULL;
+	struct udevice *regulator;
+	int ret;
+
+	debug("%s: ctrl '%s' port %d enable %s\n", __func__,
+	      dev_read_name(dev), req_index, enable ? "true" : "false");
+
+	ret = dev_read_string_index(dev, "xhci,port-power", index, &regname);
+	if (ret < 0) {
+		debug("%s: ctrl '%s' port %d: no entry in 'xhci,port-power'\n",
+		      __func__, dev_read_name(dev), req_index);
+		return ret;
+	}
+
+	ret = regulator_get_by_platname(regname, &regulator);
+	if (ret) {
+		debug("%s: ctrl '%s' port %d: could not get regulator '%s'\n",
+		      __func__, dev_read_name(dev), req_index, regname);
+		return ret;
+	}
+
+	regulator_set_enable(regulator, enable);
+#endif
+	return 0;
+}
+
+static int xhci_board_port_poweron(struct xhci_ctrl *ctrl, int req_index)
+{
+	return xhci_board_port_powerset(ctrl, req_index, true);
+}
+
+static int xhci_board_port_poweroff(struct xhci_ctrl *ctrl, int req_index)
+{
+	return xhci_board_port_powerset(ctrl, req_index, false);
+}
+
+/**
  * Submits the Requests to the XHCI Host Controller
  *
  * @param udev pointer to the USB device structure
@@ -1036,6 +1089,7 @@ static int xhci_submit_root(struct usb_device *udev, unsigned long pipe,
 			xhci_writel(status_reg, reg);
 			break;
 		case USB_PORT_FEAT_POWER:
+			xhci_board_port_poweron(ctrl, le16_to_cpu(req->index));
 			reg |= PORT_POWER;
 			xhci_writel(status_reg, reg);
 			break;
@@ -1056,6 +1110,7 @@ static int xhci_submit_root(struct usb_device *udev, unsigned long pipe,
 			reg &= ~PORT_PE;
 			break;
 		case USB_PORT_FEAT_POWER:
+			xhci_board_port_poweroff(ctrl, le16_to_cpu(req->index));
 			reg &= ~PORT_POWER;
 			break;
 		case USB_PORT_FEAT_C_RESET:
-- 
2.1.4