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@amd.com>
Signed-off-by: Sanath S <Sanath.S@amd.com>
---
 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.
+ * @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.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int tb_switch_reset_ports(struct tb_switch *sw)
+{
+	struct tb_port *port;
+	int ret = -EOPNOTSUPP;
+
+	tb_switch_for_each_port(sw, port) {
+		if (tb_port_is_null(port) && port->cap_usb4)
+			return tb_port_reset(port);
+	}
+	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;
+	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;
+	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;
+
+	val &= ~PORT_CS_19_DPR;
+	ret = tb_port_write(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+
+	return ret;
+}
+
 /**
  * usb4_port_unlock() - Unlock USB4 downstream port
  * @port: USB4 port to unlock
-- 
2.34.1

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@amd.com>
> Signed-off-by: Sanath S <Sanath.S@amd.com>
> ---
>  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 '.'

> + * @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.

> + *
> + * 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;

> +
> +	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? :(

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.

> +	}
> +	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.

> +	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 &= ~..

> +	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?

> +
> +	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);

> +}
> +
>  /**
>   * usb4_port_unlock() - Unlock USB4 downstream port
>   * @port: USB4 port to unlock
> -- 
> 2.34.1

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@amd.com>
>> Signed-off-by: Sanath S <Sanath.S@amd.com>
>> ---
>>   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

On Wed, Dec 13, 2023 at 05:28:12PM +0530, Sanath S wrote:
> 
> 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@amd.com>
> > > Signed-off-by: Sanath S <Sanath.S@amd.com>
> > > ---
> > >   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.

Did you test so that you had the thing plugged to a second USB4 port of
the host router? I don't think so because the above is only run for the
first port and then it immediately returns so all the other USB4 ports
will not be reset.

> > 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.

Okay.

> > > +
> > > +	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

On 12/12/2023 13:16, 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@amd.com>
> Signed-off-by: Sanath S <Sanath.S@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>   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.
> + * @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.
> + *
> + * Return: Returns 0 on success or an error code on failure.
> + */
> +int tb_switch_reset_ports(struct tb_switch *sw)
> +{
> +	struct tb_port *port;
> +	int ret = -EOPNOTSUPP;
> +
> +	tb_switch_for_each_port(sw, port) {
> +		if (tb_port_is_null(port) && port->cap_usb4)
> +			return tb_port_reset(port);
> +	}
> +	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;
> +	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;
> +	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;
> +
> +	val &= ~PORT_CS_19_DPR;
> +	ret = tb_port_write(port, &val, TB_CFG_PORT,
> +			port->cap_usb4 + PORT_CS_19, 1);
> +
> +	return ret;
> +}
> +
>   /**
>    * usb4_port_unlock() - Unlock USB4 downstream port
>    * @port: USB4 port to unlock