[PATCH 0/3] phy: sophgo: Add USB role switch for CV18XX/SG200X

[PATCH 0/3] phy: sophgo: Add USB role switch for CV18XX/SG200X

[Chen-Yu Yeh]

This makes one DTB work as both USB host and USB device on the Milk-V
Duo 256M, following the discussion in the thread "Milk-V Duo 256M: USB
peripheral mode works on mainline, how should dr_mode be handled?" on
the sophgo list. There, Inochi pointed out that a dual-role switch is the
right way and that the default should match the vendor image.

The usb-role-switch support in dwc2 hangs on this SoC. It clears B-valid
through the GOTGCTL session overrides while VBUS is present, and
GOTGINT.SesEndDet then fires back to back. The vendor kernel writes only
the ID override in the top syscon and lets dwc2 follow the Connector ID
change, and this works on mainline too, without any change to dwc2. So
the role switch lives in the PHY driver, which already owns those bits.

Test setup
==========

Milk-V Duo 256M, vendor buildroot rootfs, loaded by hand from U-Boot.
Tree: v7.3-rc5 with these changes, CONFIG_USB_DWC2_DUAL_ROLE=y,
CONFIG_USB_ETH=y. The series itself is based on current master; the files
touched by patches 1 and 2 are the same in both trees.

Tests 1 to 3 ran with CONFIG_USB_DWC2_DEBUG=y and the DT properties
applied through an overlay. Test 4 ran with debug disabled and the
board DTS from patch 3.

In the logs below, 
R=/sys/class/usb_role/3000000.syscon:phy@48-role-switch

1. Default peripheral, bare board on a PC, nothing done after boot
------------------------------------------------------------------

  # ls /sys/class/usb_role/
  3000000.syscon:phy@48-role-switch
  # cat $R/role
  device
  # devmem 0x03000048 32
  0x000003C0
  # cat /sys/class/udc/*/state
  configured

  PC$ lsusb | grep 0525
  Bus 003 Device 009: ID 0525:a4a2 Netchip Technology, Inc. Linux-USB Ethernet/RNDIS Gadget

2. Switching at runtime, same setup
-----------------------------------

  # echo host > $R/role
  # cat $R/role
  host
  # devmem 0x03000048 32
  0x00000142
  # echo device > $R/role
  # cat $R/role
  device
  # devmem 0x03000048 32
  0x000003C0
  # cat /sys/class/udc/*/state
  configured

The switch was repeated without an interrupt storm, then:

  # echo none > $R/role
  # cat $R/role
  device
  # devmem 0x03000048 32
  0x000003C0

3. Default host, on the USB & Ethernet IO board, nothing done after boot
------------------------------------------------------------------------

Only role-switch-default-mode differs from patch 3 here.

  [    3.409672] usb 1-1: new high-speed USB device number 2 using dwc2
  [    3.666655] hub 1-1:1.0: 4 ports detected
  [   72.484979] usb 1-1.1: new high-speed USB device number 3 using dwc2
  [   74.804484]  sda: sda1 sda2 sda3 sda4

The USB stick was plugged in by hand at about 72 s.

  # cat $R/role
  host
  # devmem 0x03000048 32
  0x00000142
  # devmem 0x04340018 32
  0xF300081E
  # devmem 0x04340440 32
  0x00001005
  # echo none > $R/role
  # cat $R/role
  host
  # ls /dev/sd*
  /dev/sda  /dev/sda1  /dev/sda2  /dev/sda3  /dev/sda4

4. Patch 3 as committed, debug disabled
---------------------------------------

Bare board on a PC, nothing done after boot:

  # cat $R/role
  device

  PC: usb 3-9: New USB device found, idVendor=0525, idProduct=a4a2
  PC: usb 3-9: Product: RNDIS/Ethernet Gadget

On the IO board, with a USB stick already plugged in at boot:

  # cat $R/role
  device
  # echo host > $R/role
  # cat $R/role
  host
  # dmesg | grep -E 'usb 1-1'
  [  415.464739] usb 1-1: new high-speed USB device number 2 using dwc2
  [  415.940738] usb 1-1.1: new high-speed USB device number 3 using dwc2

Before this series
==================

With usb-role-switch on the dwc2 node, "echo host" hangs the board in the
SesEndDet storm, and so does boot without role-switch-default-mode.

With dr_mode = "otg" and no role switch, writing the ID override by hand
worked:

  devmem 0x03000048 32 0x3C0  -> high-speed RNDIS gadget on the PC
  devmem 0x03000048 32 0x142  -> disconnects from the PC, host side starts

Three round trips were all correct, and ping over usb0 afterwards was
5/5. On the IO board, the hub and USB stick appeared after one toggle,
but not at boot, because usb_add_hcd() moved the PHY to host after dwc2
had already set up for device:

            at boot       after one toggle
  GINTSTS   0x05000023    0x04200021
  GINTMSK   0xd0bc3cd4    0xf300081e    (PrtInt masked -> unmasked)
  HPRT0     0x00021403    0x00001005    (ConnDet pending -> port enabled)

Test 3 above reaches the right-hand values at boot without a toggle.

Not tested
==========

 - A USB stick already plugged in at boot in the default host case.
 - Running on a master based tree: all tests used the v7.3-rc5 tree.
 - Boards other than the Duo 256M. Nothing changes on them, since the
   role switch is only registered when the PHY node has usb-role-switch.

Question
========

With patch 3, the hub on the IO board needs "echo host" after each boot.
Should the IO board overlay (sg2002-milkv-duo256m-eth.dtso) set
role-switch-default-mode = "host", or should it stay the same as the
vendor image?


Chen-Yu Yeh (3):
  dt-bindings: phy: sophgo,cv1800b-usb2-phy: Add USB role switch
    properties
  phy: sophgo: Add USB role switch support for CV18XX/SG200X
  riscv: dts: sophgo: sg2002-milkv-duo256m: Enable USB role switch

 .../bindings/phy/sophgo,cv1800b-usb2-phy.yaml |  11 ++
 .../boot/dts/sophgo/sg2002-milkv-duo256m.dts  |   7 +-
 drivers/phy/sophgo/Kconfig                    |   2 +
 drivers/phy/sophgo/phy-cv1800-usb2.c          | 107 ++++++++++++++++--
 4 files changed, 119 insertions(+), 8 deletions(-)


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.43.0

[PATCH 1/3] dt-bindings: phy: sophgo,cv1800b-usb2-phy: Add USB role switch properties

[Chen-Yu Yeh]

The USB role on CV18XX/SG200X is selected by the ID override in the top
syscon, which belongs to this PHY, so the PHY is what provides the role
switch.

Allow usb-role-switch and role-switch-default-mode on the PHY node. The
default mode only has a meaning when the role switch is present.

Signed-off-by: Chen-Yu Yeh <chenyou910331@gmail.com>
---
 .../bindings/phy/sophgo,cv1800b-usb2-phy.yaml         | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/phy/sophgo,cv1800b-usb2-phy.yaml b/Documentation/devicetree/bindings/phy/sophgo,cv1800b-usb2-phy.yaml
index 2ff8f85d0282..a1d164686b07 100644
--- a/Documentation/devicetree/bindings/phy/sophgo,cv1800b-usb2-phy.yaml
+++ b/Documentation/devicetree/bindings/phy/sophgo,cv1800b-usb2-phy.yaml
@@ -34,6 +34,15 @@ properties:
   resets:
     maxItems: 1
 
+  usb-role-switch:
+    $ref: /schemas/usb/usb-drd.yaml#/properties/usb-role-switch
+
+  role-switch-default-mode:
+    $ref: /schemas/usb/usb-drd.yaml#/properties/role-switch-default-mode
+
+dependencies:
+  role-switch-default-mode: [ usb-role-switch ]
+
 required:
   - compatible
   - "#phy-cells"
@@ -51,4 +60,6 @@ examples:
       clocks = <&clk 93>, <&clk 94>, <&clk 95>;
       clock-names = "app", "stb", "lpm";
       resets = <&rst 58>;
+      usb-role-switch;
+      role-switch-default-mode = "peripheral";
     };
-- 
2.43.0

[PATCH 2/3] phy: sophgo: Add USB role switch support for CV18XX/SG200X

[Chen-Yu Yeh]

The USB role of the dwc2 controller on CV18XX/SG200X is selected by the
ID override in the top syscon (offset 0x48, bits 6 and 7). The vendor
kernel switches roles by writing only this override, and dwc2 follows
through its Connector ID status change handling.

The usb-role-switch support in dwc2 does not work on this SoC. It
switches roles through the GOTGCTL session overrides, and clearing
B-valid while the core is a B-device with VBUS present makes
GOTGINT.SesEndDet fire back to back, which hangs the board in the
interrupt handler. This happens on "echo host" and at probe without
role-switch-default-mode.

Register a role switch in the PHY driver when the PHY node has
usb-role-switch, and write only the ID override when the role changes.

There are two ordering details:

 - Set the default role before registering the PHY provider, so dwc2
   already sees the final role when it probes. Otherwise it records the
   role it sees at probe and keeps the interrupt mask of that role.

 - Ignore phy_set_mode() while the role switch is in use, because
   usb_add_hcd() asks for host mode on any controller that has a host
   side, which would override the default role.

The ID has no "unattached" state, so USB_ROLE_NONE selects the default
role.

Move the register write to a helper shared with the set_mode callback,
and update PHY_VBUS_POWER and the ID override in a single write.

Tested on Milk-V Duo 256M with dr_mode = "otg" and a v7.3-rc5 based tree:

  Default peripheral, bare board on a PC, no manual step after boot:
    role device, 0x03000048 = 0x3c0, UDC configured, PC sees 0525:a4a2
    echo host:   role host, 0x03000048 = 0x142
    echo device: role device, 0x03000048 = 0x3c0, UDC configured
    echo none:   role device, 0x03000048 = 0x3c0

  Default host, on the USB & Ethernet IO board, no manual step after boot:
    role host, 0x03000048 = 0x142, the hub enumerates at 3.4 s, a USB
    stick plugged in later shows up as sda

Registers at boot in the host case, before and after this change:

            before        after
  GINTMSK   0xd0bc3cd4    0xf300081e    (PrtInt masked -> unmasked)
  HPRT0     0x00021403    0x00001005    (ConnDet pending -> port enabled)

Signed-off-by: Chen-Yu Yeh <chenyou910331@gmail.com>
---
 drivers/phy/sophgo/Kconfig           |   2 +
 drivers/phy/sophgo/phy-cv1800-usb2.c | 107 +++++++++++++++++++++++++--
 2 files changed, 102 insertions(+), 7 deletions(-)

diff --git a/drivers/phy/sophgo/Kconfig b/drivers/phy/sophgo/Kconfig
index 2c943bbe1f81..055cbcd32891 100644
--- a/drivers/phy/sophgo/Kconfig
+++ b/drivers/phy/sophgo/Kconfig
@@ -10,6 +10,8 @@ config PHY_SOPHGO_CV1800_USB2
 	depends on MFD_SYSCON
 	depends on USB_SUPPORT
 	select GENERIC_PHY
+	select USB_COMMON
+	select USB_ROLE_SWITCH
 	help
 	  Enable this to support the USB 2.0 PHY used with
 	  the DWC2 USB controller in Sophgo CV18XX/SG200X
diff --git a/drivers/phy/sophgo/phy-cv1800-usb2.c b/drivers/phy/sophgo/phy-cv1800-usb2.c
index 6fe846534e9c..b4c27ab41a6f 100644
--- a/drivers/phy/sophgo/phy-cv1800-usb2.c
+++ b/drivers/phy/sophgo/phy-cv1800-usb2.c
@@ -13,8 +13,11 @@
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/phy/phy.h>
+#include <linux/property.h>
 #include <linux/regmap.h>
 #include <linux/spinlock.h>
+#include <linux/usb/otg.h>
+#include <linux/usb/role.h>
 
 #define REG_USB_PHY_CTRL		0x048
 
@@ -37,8 +40,93 @@ struct cv1800_usb_phy {
 	struct clk	*usb_lpm_clk;
 	struct clk	*usb_stb_clk;
 	bool		support_otg;
+	struct usb_role_switch	*role_sw;
+	enum usb_role		default_role;
 };
 
+static int cv1800_usb_phy_set_id(struct cv1800_usb_phy *phy, enum usb_role role)
+{
+	unsigned int regval;
+
+	switch (role) {
+	case USB_ROLE_DEVICE:
+		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_DEVICE;
+		break;
+	case USB_ROLE_HOST:
+		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_HOST |
+			 PHY_VBUS_POWER;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(phy->syscon, REG_USB_PHY_CTRL,
+				  PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE |
+				  PHY_VBUS_POWER, regval);
+}
+
+static int cv1800_usb_phy_role_set(struct usb_role_switch *sw, enum usb_role role)
+{
+	struct cv1800_usb_phy *phy = usb_role_switch_get_drvdata(sw);
+
+	if (role == USB_ROLE_NONE)
+		role = phy->default_role;
+
+	return cv1800_usb_phy_set_id(phy, role);
+}
+
+static enum usb_role cv1800_usb_phy_role_get(struct usb_role_switch *sw)
+{
+	struct cv1800_usb_phy *phy = usb_role_switch_get_drvdata(sw);
+	unsigned int val = 0;
+	int ret = regmap_read(phy->syscon, REG_USB_PHY_CTRL, &val);
+
+	if (ret)
+		return USB_ROLE_NONE;
+
+	if (val & PHY_ID_OVERWRITE_MODE)
+		return USB_ROLE_DEVICE;
+
+	return USB_ROLE_HOST;
+}
+
+static void cv1800_usb_phy_role_unregister(void *data)
+{
+	usb_role_switch_unregister(data);
+}
+
+static int cv1800_usb_phy_setup_role_switch(struct device *dev,
+					    struct cv1800_usb_phy *phy)
+{
+	struct usb_role_switch_desc desc = {
+		.fwnode = dev_fwnode(dev),
+		.set = cv1800_usb_phy_role_set,
+		.get = cv1800_usb_phy_role_get,
+		.allow_userspace_control = true,
+		.driver_data = phy,
+	};
+	int ret;
+
+	if (!device_property_read_bool(dev, "usb-role-switch"))
+		return 0;
+
+	if (usb_get_role_switch_default_mode(dev) == USB_DR_MODE_HOST)
+		phy->default_role = USB_ROLE_HOST;
+	else
+		phy->default_role = USB_ROLE_DEVICE;
+
+	ret = cv1800_usb_phy_set_id(phy, phy->default_role);
+	if (ret)
+		return ret;
+
+	phy->role_sw = usb_role_switch_register(dev, &desc);
+	if (IS_ERR(phy->role_sw))
+		return PTR_ERR(phy->role_sw);
+
+	return devm_add_action_or_reset(dev, cv1800_usb_phy_role_unregister,
+					phy->role_sw);
+}
+
 static int cv1800_usb_phy_set_mode(struct phy *_phy,
 				   enum phy_mode mode, int submode)
 {
@@ -46,17 +134,17 @@ static int cv1800_usb_phy_set_mode(struct phy *_phy,
 	unsigned int regval = 0;
 	int ret;
 
+	/* The role switch owns the ID override */
+	if (phy->role_sw)
+		return 0;
+
 	dev_info(&phy->phy->dev, "set mode %d", (int)mode);
 
 	switch (mode) {
 	case PHY_MODE_USB_DEVICE:
-		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_DEVICE;
-		regmap_clear_bits(phy->syscon, REG_USB_PHY_CTRL, PHY_VBUS_POWER);
-		break;
+		return cv1800_usb_phy_set_id(phy, USB_ROLE_DEVICE);
 	case PHY_MODE_USB_HOST:
-		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_HOST;
-		regmap_set_bits(phy->syscon, REG_USB_PHY_CTRL, PHY_VBUS_POWER);
-		break;
+		return cv1800_usb_phy_set_id(phy, USB_ROLE_HOST);
 	case PHY_MODE_USB_OTG:
 		if (!phy->support_otg)
 			return 0;
@@ -107,7 +195,7 @@ static int cv1800_usb_phy_probe(struct platform_device *pdev)
 	if (!parent)
 		return -ENODEV;
 
-	phy = devm_kmalloc(dev, sizeof(*phy), GFP_KERNEL);
+	phy = devm_kzalloc(dev, sizeof(*phy), GFP_KERNEL);
 	if (!phy)
 		return -ENOMEM;
 
@@ -144,6 +232,11 @@ static int cv1800_usb_phy_probe(struct platform_device *pdev)
 		return ret;
 
 	phy_set_drvdata(phy->phy, phy);
+
+	ret = cv1800_usb_phy_setup_role_switch(dev, phy);
+	if (ret)
+		return ret;
+
 	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
 
 	return PTR_ERR_OR_ZERO(phy_provider);
-- 
2.43.0

[PATCH 3/3] riscv: dts: sophgo: sg2002-milkv-duo256m: Enable USB role switch

[Chen-Yu Yeh]

The USB-C port of the Milk-V Duo 256M is the only USB connector on the
bare board, and the vendor image uses it in device mode by default.
Host mode is mainly needed with the USB & Ethernet IO board, whose USB
hub hangs off the same controller.

Use the role switch in the PHY so that one DTB can do both, and default
to peripheral to match the vendor image.

This changes the default of the port from host to device. To use host
mode, including the hub on the IO board, select it at runtime:

  echo host > /sys/class/usb_role/3000000.syscon:phy@48-role-switch/role

Signed-off-by: Chen-Yu Yeh <chenyou910331@gmail.com>
---
 arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts b/arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts
index d4e86c15664e..0ad1dfd9449c 100644
--- a/arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts
+++ b/arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts
@@ -105,6 +105,11 @@ &uart0 {
 };
 
 &usb {
-	dr_mode = "host";
+	dr_mode = "otg";
 	status = "okay";
 };
+
+&usbphy {
+	usb-role-switch;
+	role-switch-default-mode = "peripheral";
+};
-- 
2.43.0