[RFC] net: dsa: microchip: add KSZ8 change_tag_protocol support

[RFC] net: dsa: microchip: add KSZ8 change_tag_protocol support

[vtpieter]

From: Pieter Van Trappen <pieter.van.trappen@cern.ch>

Add support for changing the KSZ8 switches tag protocol. In fact
these devices can only enable or disable the tail tag, so there's
really only three supported protocols:
- DSA_TAG_PROTO_KSZ8795 for KSZ87xx
- DSA_TAG_PROTO_KSZ9893 for KSZ88x3
- DSA_TAG_PROTO_NONE

When disabled, this can be used as a workaround for the 'Common
pitfalls using DSA setups' [1] to use the conduit network interface as
a regular one, admittedly forgoing most DSA functionality and using
the device as an unmanaged switch whilst allowing control
operations (ethtool, PHY management, WoL). Implementing the new
software-defined DSA tagging protocol tag_8021q [2] for these devices
seems overkill for this use case at the time being.

Link: Documentation/networking/dsa/dsa.rst [1]
Link: https://lpc.events/event/11/contributions/949/attachments/823/1555/paper.pdf [2]
Signed-off-by: Pieter Van Trappen <pieter.van.trappen@cern.ch>
---
 .../devicetree/bindings/net/dsa/dsa-port.yaml |  1 +
 drivers/net/dsa/microchip/ksz8.h              |  2 ++
 drivers/net/dsa/microchip/ksz8795.c           | 28 +++++++++++++++++++
 drivers/net/dsa/microchip/ksz_common.c        | 19 +++++++++++--
 drivers/net/dsa/microchip/ksz_common.h        |  2 ++
 5 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
index 480120469953..ded8019b6ba6 100644
--- a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
@@ -53,6 +53,7 @@ properties:
     enum:
       - dsa
       - edsa
+      - none
       - ocelot
       - ocelot-8021q
       - rtl8_4
diff --git a/drivers/net/dsa/microchip/ksz8.h b/drivers/net/dsa/microchip/ksz8.h
index ae43077e76c3..802cb9d657bb 100644
--- a/drivers/net/dsa/microchip/ksz8.h
+++ b/drivers/net/dsa/microchip/ksz8.h
@@ -54,6 +54,8 @@ int ksz8_reset_switch(struct ksz_device *dev);
 int ksz8_switch_init(struct ksz_device *dev);
 void ksz8_switch_exit(struct ksz_device *dev);
 int ksz8_change_mtu(struct ksz_device *dev, int port, int mtu);
+int ksz8_change_tag_protocol(struct ksz_device *dev,
+			     enum dsa_tag_protocol proto);
 void ksz8_phylink_mac_link_up(struct phylink_config *config,
 			      struct phy_device *phydev, unsigned int mode,
 			      phy_interface_t interface, int speed, int duplex,
diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
index d27b9c36d73f..0704d5404c5b 100644
--- a/drivers/net/dsa/microchip/ksz8795.c
+++ b/drivers/net/dsa/microchip/ksz8795.c
@@ -127,6 +127,34 @@ int ksz8_change_mtu(struct ksz_device *dev, int port, int mtu)
 	return -EOPNOTSUPP;
 }
 
+/**
+ * ksz8_change_tag_protocol - Change tag protocol
+ * @dev: The device structure.
+ * @proto: The requested protocol.
+ *
+ * This function allows changing the tag protocol. In fact the ksz8
+ * devices can only enable or disable the tail tag, so there's really
+ * only 2 supported protocols.
+ *
+ * Return: 0 on success, -EPROTONOSUPPORT in case protocol not supported.
+ */
+int ksz8_change_tag_protocol(struct ksz_device *dev,
+			     enum dsa_tag_protocol proto)
+{
+	const u32 *masks = dev->info->masks;
+	const u16 *regs = dev->info->regs;
+
+	if ( (proto == DSA_TAG_PROTO_KSZ8795 && ksz_is_ksz87xx(dev)) ||
+	     (proto == DSA_TAG_PROTO_KSZ9893 && ksz_is_ksz88x3(dev)) )
+		ksz_cfg(dev, regs[S_TAIL_TAG_CTRL], masks[SW_TAIL_TAG_ENABLE], true);
+	else if (proto == DSA_TAG_PROTO_NONE)
+		ksz_cfg(dev, regs[S_TAIL_TAG_CTRL], masks[SW_TAIL_TAG_ENABLE], false);
+	else
+		return -EPROTONOSUPPORT;
+
+	return 0;
+}
+
 static int ksz8_port_queue_split(struct ksz_device *dev, int port, int queues)
 {
 	u8 mask_4q, mask_2q;
diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 1491099528be..a87f43908a9a 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -307,6 +307,7 @@ static const struct ksz_dev_ops ksz8_dev_ops = {
 	.init = ksz8_switch_init,
 	.exit = ksz8_switch_exit,
 	.change_mtu = ksz8_change_mtu,
+	.change_tag_protocol = ksz8_change_tag_protocol,
 };
 
 static void ksz9477_phylink_mac_link_up(struct phylink_config *config,
@@ -2893,9 +2894,7 @@ static enum dsa_tag_protocol ksz_get_tag_protocol(struct dsa_switch *ds,
 	struct ksz_device *dev = ds->priv;
 	enum dsa_tag_protocol proto = DSA_TAG_PROTO_NONE;
 
-	if (dev->chip_id == KSZ8795_CHIP_ID ||
-	    dev->chip_id == KSZ8794_CHIP_ID ||
-	    dev->chip_id == KSZ8765_CHIP_ID)
+	if (ksz_is_ksz87xx(dev))
 		proto = DSA_TAG_PROTO_KSZ8795;
 
 	if (dev->chip_id == KSZ8830_CHIP_ID ||
@@ -2917,12 +2916,25 @@ static enum dsa_tag_protocol ksz_get_tag_protocol(struct dsa_switch *ds,
 	return proto;
 }
 
+static int ksz_change_tag_protocol(struct dsa_switch *ds,
+				   enum dsa_tag_protocol proto)
+{
+	struct ksz_device *dev = ds->priv;
+
+	if (dev->dev_ops->change_tag_protocol)
+		return dev->dev_ops->change_tag_protocol(dev, proto);
+	else
+		return -EPROTONOSUPPORT;
+}
+
 static int ksz_connect_tag_protocol(struct dsa_switch *ds,
 				    enum dsa_tag_protocol proto)
 {
 	struct ksz_tagger_data *tagger_data;
 
 	switch (proto) {
+	case DSA_TAG_PROTO_NONE:
+		return 0;
 	case DSA_TAG_PROTO_KSZ8795:
 		return 0;
 	case DSA_TAG_PROTO_KSZ9893:
@@ -3974,6 +3986,7 @@ static int ksz_hsr_leave(struct dsa_switch *ds, int port,
 
 static const struct dsa_switch_ops ksz_switch_ops = {
 	.get_tag_protocol	= ksz_get_tag_protocol,
+	.change_tag_protocol    = ksz_change_tag_protocol,
 	.connect_tag_protocol   = ksz_connect_tag_protocol,
 	.get_phy_flags		= ksz_get_phy_flags,
 	.setup			= ksz_setup,
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index 5f0a628b9849..badae22f4613 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -354,6 +354,8 @@ struct ksz_dev_ops {
 	void (*get_caps)(struct ksz_device *dev, int port,
 			 struct phylink_config *config);
 	int (*change_mtu)(struct ksz_device *dev, int port, int mtu);
+	int (*change_tag_protocol)(struct ksz_device *dev,
+				   enum dsa_tag_protocol proto);
 	void (*freeze_mib)(struct ksz_device *dev, int port, bool freeze);
 	void (*port_init_cnt)(struct ksz_device *dev, int port);
 	void (*phylink_mac_link_up)(struct ksz_device *dev, int port,

base-commit: dd1bf9f9df156b43e5122f90d97ac3f59a1a5621
-- 
2.43.0

Re: [RFC] net: dsa: microchip: add KSZ8 change_tag_protocol support

[Krzysztof Kozlowski]

On 16/08/2024 08:59, vtpieter@gmail.com wrote:
> From: Pieter Van Trappen <pieter.van.trappen@cern.ch>
> 
> Add support for changing the KSZ8 switches tag protocol. In fact
> these devices can only enable or disable the tail tag, so there's
> really only three supported protocols:
> - DSA_TAG_PROTO_KSZ8795 for KSZ87xx
> - DSA_TAG_PROTO_KSZ9893 for KSZ88x3
> - DSA_TAG_PROTO_NONE
> 
> When disabled, this can be used as a workaround for the 'Common
> pitfalls using DSA setups' [1] to use the conduit network interface as
> a regular one, admittedly forgoing most DSA functionality and using
> the device as an unmanaged switch whilst allowing control
> operations (ethtool, PHY management, WoL). Implementing the new
> software-defined DSA tagging protocol tag_8021q [2] for these devices
> seems overkill for this use case at the time being.
> 
> Link: Documentation/networking/dsa/dsa.rst [1]
> Link: https://lpc.events/event/11/contributions/949/attachments/823/1555/paper.pdf [2]
> Signed-off-by: Pieter Van Trappen <pieter.van.trappen@cern.ch>
> ---
>  .../devicetree/bindings/net/dsa/dsa-port.yaml |  1 +
>  drivers/net/dsa/microchip/ksz8.h              |  2 ++
>  drivers/net/dsa/microchip/ksz8795.c           | 28 +++++++++++++++++++
>  drivers/net/dsa/microchip/ksz_common.c        | 19 +++++++++++--
>  drivers/net/dsa/microchip/ksz_common.h        |  2 ++
>  5 files changed, 49 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
> index 480120469953..ded8019b6ba6 100644
> --- a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
> +++ b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
> @@ -53,6 +53,7 @@ properties:
>      enum:
>        - dsa
>        - edsa
> +      - none
>        - ocelot
>        - ocelot-8021q
>        - rtl8_4

Please run scripts/checkpatch.pl and fix reported warnings. Then please
run `scripts/checkpatch.pl --strict` and (probably) fix more warnings.
Some warnings can be ignored, especially from --strict run, but the code
here looks like it needs a fix. Feel free to get in touch if the warning
is not clear.

Anyway, what does "none" mean in terms of protocol? Is there a "none"
protocol? Or you mean, disable tagging entirely?

Best regards,
Krzysztof

Re: [RFC] net: dsa: microchip: add KSZ8 change_tag_protocol support

[Pieter]

On Friday 16 August 2024 at 09:12, Krzysztof Kozlowski <krzk@kernel.org> wrote:
>
> On 16/08/2024 08:59, vtpieter@gmail.com wrote:
> > From: Pieter Van Trappen <pieter.van.trappen@cern.ch>
> >
> > Add support for changing the KSZ8 switches tag protocol. In fact
> > these devices can only enable or disable the tail tag, so there's
> > really only three supported protocols:
> > - DSA_TAG_PROTO_KSZ8795 for KSZ87xx
> > - DSA_TAG_PROTO_KSZ9893 for KSZ88x3
> > - DSA_TAG_PROTO_NONE
> >
> > --- a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
> > +++ b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml
> > @@ -53,6 +53,7 @@ properties:
> >      enum:
> >        - dsa
> >        - edsa
> > +      - none
> >        - ocelot
> >        - ocelot-8021q
> >        - rtl8_4
>
> Please run scripts/checkpatch.pl and fix reported warnings. Then please
> run `scripts/checkpatch.pl --strict` and (probably) fix more warnings.
> Some warnings can be ignored, especially from --strict run, but the code
> here looks like it needs a fix. Feel free to get in touch if the warning
> is not clear.

Hi Krzysztof, thanks indeed I forgot to run it after my last modifications.
I am aware that the dt-binding patch should be separate, I just thought
it'd make more sense for this RFC to have these together.

> Anyway, what does "none" mean in terms of protocol? Is there a "none"
> protocol? Or you mean, disable tagging entirely?

Indeed the 'none' protocol is DSA_TAG_PROTO_NONE which means
disable tagging entirely. The concept with advantages and disadvantages
is well described in the paper with link which i part of the commit message.

Cheers, Pieter