Re: [Patch v2 1/2] thunderbolt: Introduce tb_switch_reset_ports(), tb_port_reset() and usb4_port_reset()

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On 12/13/2023 11:29 AM, Mika Westerberg wrote:
On Wed, Dec 13, 2023 at 12:46:34AM +0530, Sanath S wrote:
Introduce the tb_switch_reset_ports() function that resets the
downstream ports of a given switch. This helps us reset the USB4
links created by boot firmware during the init sequence.

Introduce the tb_port_reset() helper function that resets the
given port.

Introduce the usb4_port_reset() function that performs the DPR
of a given port. This function follows the CM guide specification 7.3

Suggested-by: Mario Limonciello <mario.limonciello@xxxxxxx>
Signed-off-by: Sanath S <Sanath.S@xxxxxxx>
---
  drivers/thunderbolt/switch.c  | 35 +++++++++++++++++++++++++++++++
  drivers/thunderbolt/tb.h      |  2 ++
  drivers/thunderbolt/tb_regs.h |  1 +
  drivers/thunderbolt/usb4.c    | 39 +++++++++++++++++++++++++++++++++++
  4 files changed, 77 insertions(+)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 44e9b09de47a..ef7ed92fd48e 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -626,6 +626,19 @@ int tb_port_unlock(struct tb_port *port)
  	return 0;
  }
+/**
+ * tb_port_reset() - Reset downstream port
+ * @port: Port to reset
+ *
+ * Helps to reconfigure the USB4 link by resetting the downstream port.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+static int tb_port_reset(struct tb_port *port)
+{
+	return usb4_port_reset(port);
+}
+
  static int __tb_port_enable(struct tb_port *port, bool enable)
  {
  	int ret;
@@ -1547,6 +1560,28 @@ static void tb_dump_switch(const struct tb *tb, const struct tb_switch *sw)
  	       regs->__unknown1, regs->__unknown4);
  }
+/**
+ * tb_switch_reset_ports() - Reset downstream ports of switch.
Drop the '.'
Ack.
+ * @sw: Switch whose ports need to be reset.
+ *
+ * This is applicable only for USB4 routers.
+ * tb_switch_is_usb4() needs to be called before calling this
+ * function.
This should fit into 2 lines:

	* This is applicable only for USB4 routers. tb_switch_is_usb4()
	* needs to be called before calling this function.
Ack.
+ *
+ * Return: Returns 0 on success or an error code on failure.
Specifically returns %-EOPNOTSUPP if the router does not support this
(e.g is not USB4 router).

+ */
+int tb_switch_reset_ports(struct tb_switch *sw)
+{
+	struct tb_port *port;
+	int ret = -EOPNOTSUPP;
Reverse christmas tree:

	int ret = -EOPNOTSUPP;
	struct tb_port *port;
Ack.
+
+	tb_switch_for_each_port(sw, port) {
+		if (tb_port_is_null(port) && port->cap_usb4)
+			return tb_port_reset(port);
Now you run this only once for the first lane adapter it finds.

How much you actually tested this patch series? :(

I've tested this patch on multiple TBT4 docks like OWC, Kenningston and Lenovo on
reboot/suspend-resume/hotplug scenarios.

Since we are already in -rc5 it is unlikely that behavioral changes like
this will go to the next release (v6.8-rc1), so you have all that time
to make sure your patches work as expected.
Agreed. Since this is a behavioral change it needs more testing and refinement on how
we can reset the switch and its ports.
+	}
+	return ret;
+}
+
  /**
   * tb_switch_reset() - reconfigure route, enable and send TB_CFG_PKG_RESET
   * @sw: Switch to reset
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index e299e53473ae..f2687ec4ac53 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -797,6 +797,7 @@ void tb_switch_remove(struct tb_switch *sw);
  void tb_switch_suspend(struct tb_switch *sw, bool runtime);
  int tb_switch_resume(struct tb_switch *sw);
  int tb_switch_reset(struct tb_switch *sw);
+int tb_switch_reset_ports(struct tb_switch *sw);
  int tb_switch_wait_for_bit(struct tb_switch *sw, u32 offset, u32 bit,
  			   u32 value, int timeout_msec);
  void tb_sw_set_unplugged(struct tb_switch *sw);
@@ -1281,6 +1282,7 @@ struct tb_port *usb4_switch_map_usb3_down(struct tb_switch *sw,
  int usb4_switch_add_ports(struct tb_switch *sw);
  void usb4_switch_remove_ports(struct tb_switch *sw);
+int usb4_port_reset(struct tb_port *port);
  int usb4_port_unlock(struct tb_port *port);
  int usb4_port_hotplug_enable(struct tb_port *port);
  int usb4_port_configure(struct tb_port *port);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 87e4795275fe..d49530bc0d53 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -389,6 +389,7 @@ struct tb_regs_port_header {
  #define PORT_CS_18_CSA				BIT(22)
  #define PORT_CS_18_TIP				BIT(24)
  #define PORT_CS_19				0x13
+#define PORT_CS_19_DPR				BIT(0)
  #define PORT_CS_19_PC				BIT(3)
  #define PORT_CS_19_PID				BIT(4)
  #define PORT_CS_19_WOC				BIT(16)
diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index 4277733d0021..c8a4bf33ed1c 100644
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -1073,6 +1073,45 @@ void usb4_switch_remove_ports(struct tb_switch *sw)
  	}
  }
+/**
+ * usb4_port_reset() - Reset USB4 downsteam port
+ * @port: USB4 port to reset.
+ *
+ * Helps to reconfigure USB4 link by resetting downstream port.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int usb4_port_reset(struct tb_port *port)
+{
+	u32 val = 0;
This initialization is actually not needed.
Ack.

+	int ret;
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	val = val | PORT_CS_19_DPR;
val |= PORT_CS_19_DPR;

Same as you do below with &= ~..
Ack.

+	ret = tb_port_write(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	/* Wait for 10ms after requesting downstream port reset */
+	usleep_range(10000, 15000);
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
Do you really need to read it back from the hardware here?

I don't think it's necessary. But I added this just to be safe if performing DPR has
made changes to other CS_19 bits.

+
+	val &= ~PORT_CS_19_DPR;
+	ret = tb_port_write(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+
+	return ret;
This can be simply

	return tb_port_write(port, &val, TB_CFG_PORT,
			     port->cap_usb4 + PORT_CS_19, 1);
Ack.
+}
+
  /**
   * usb4_port_unlock() - Unlock USB4 downstream port
   * @port: USB4 port to unlock
--
2.34.1




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