[PATCH 0/3] J2 Ethernet MAC driver

[PATCH 0/3] J2 Ethernet MAC driver

[Artur Rojek]

Hi all,

this series introduces support for the Ethernet Media Access Controller
found in the J-Core family of SoCs.

Patch [1/3] documents the 'jcore,*' DT prefix. While there already exist
a few drivers that use this prefix, up to this point it remained
undocumented. 

Patch [2/3] documents Device Tree bindings for jcore,emac.

Patch [3/3] is the EMAC driver code.

This series already had a few rounds of internal review, so some of you
might find it familiar (I carried over Reviewed-by tags, where
applicable).

Artur Rojek (3):
  dt-bindings: vendor-prefixes: Document J-Core
  dt-bindings: net: Add support for J-Core EMAC
  net: j2: Introduce J-Core EMAC

 .../devicetree/bindings/net/jcore,emac.yaml   |  42 ++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 drivers/net/ethernet/Kconfig                  |  12 +
 drivers/net/ethernet/Makefile                 |   1 +
 drivers/net/ethernet/jcore_emac.c             | 391 ++++++++++++++++++
 5 files changed, 448 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/jcore,emac.yaml
 create mode 100644 drivers/net/ethernet/jcore_emac.c

-- 
2.50.1

[PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Artur Rojek]

J-Core is a clean-room open source processor and SoC design using the
SuperH instruction set.

The 'jcore' prefix is in use by IP cores originating from this design.

Link: https://j-core.org
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
---
 Documentation/devicetree/bindings/vendor-prefixes.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml
index a92261b10c52..558f51665616 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
+++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
@@ -783,6 +783,8 @@ patternProperties:
     description: Jadard Technology Inc.
   "^jasonic,.*":
     description: Jasonic Technology Ltd.
+  "^jcore,.*":
+    description: J-Core Open Processor
   "^jdi,.*":
     description: Japan Display Inc.
   "^jedec,.*":
-- 
2.50.1

[PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Artur Rojek]

Add a documentation file to describe the Device Tree bindings for the
Ethernet Media Access Controller found in the J-Core family of SoCs.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
---
 .../devicetree/bindings/net/jcore,emac.yaml   | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/jcore,emac.yaml

diff --git a/Documentation/devicetree/bindings/net/jcore,emac.yaml b/Documentation/devicetree/bindings/net/jcore,emac.yaml
new file mode 100644
index 000000000000..a4384f7ed83d
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/jcore,emac.yaml
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/jcore,emac.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: J-Core Ethernet Media Access Controller
+
+description: |
+  This node provides properties for configuring the Ethernet MAC found
+  in the J-Core family of SoCs.
+
+maintainers:
+  - Artur Rojek <contact@artur-rojek.eu>
+
+properties:
+  compatible:
+    const: jcore,emac
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+allOf:
+  - $ref: ethernet-controller.yaml#
+
+additionalProperties: false
+
+examples:
+  - |
+    ethernet@10000 {
+      compatible = "jcore,emac";
+      reg = <0x10000 0x2000>;
+      interrupts = <0x11>;
+    };
-- 
2.50.1

[PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

Add support for the Ethernet Media Access Controller found in the J-Core
family of SoCs.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
---
 drivers/net/ethernet/Kconfig      |  12 +
 drivers/net/ethernet/Makefile     |   1 +
 drivers/net/ethernet/jcore_emac.c | 391 ++++++++++++++++++++++++++++++
 3 files changed, 404 insertions(+)
 create mode 100644 drivers/net/ethernet/jcore_emac.c

diff --git a/drivers/net/ethernet/Kconfig b/drivers/net/ethernet/Kconfig
index f86d4557d8d7..0d55d8794f47 100644
--- a/drivers/net/ethernet/Kconfig
+++ b/drivers/net/ethernet/Kconfig
@@ -159,6 +159,18 @@ config ETHOC
 	help
 	  Say Y here if you want to use the OpenCores 10/100 Mbps Ethernet MAC.
 
+config JCORE_EMAC
+	tristate "J-Core Ethernet MAC support"
+	depends on CPU_J2 || COMPILE_TEST
+	depends on HAS_IOMEM
+	select REGMAP_MMIO
+	help
+	  This enables support for the Ethernet Media Access Controller found
+	  in the J-Core family of SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called jcore_emac.
+
 config OA_TC6
 	tristate "OPEN Alliance TC6 10BASE-T1x MAC-PHY support" if COMPILE_TEST
 	depends on SPI
diff --git a/drivers/net/ethernet/Makefile b/drivers/net/ethernet/Makefile
index 67182339469a..e1e03a1d47a6 100644
--- a/drivers/net/ethernet/Makefile
+++ b/drivers/net/ethernet/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_NET_VENDOR_INTEL) += intel/
 obj-$(CONFIG_NET_VENDOR_I825XX) += i825xx/
 obj-$(CONFIG_NET_VENDOR_MICROSOFT) += microsoft/
 obj-$(CONFIG_NET_VENDOR_XSCALE) += xscale/
+obj-$(CONFIG_JCORE_EMAC) += jcore_emac.o
 obj-$(CONFIG_JME) += jme.o
 obj-$(CONFIG_KORINA) += korina.o
 obj-$(CONFIG_LANTIQ_ETOP) += lantiq_etop.o
diff --git a/drivers/net/ethernet/jcore_emac.c b/drivers/net/ethernet/jcore_emac.c
new file mode 100644
index 000000000000..fbfac4b16d6d
--- /dev/null
+++ b/drivers/net/ethernet/jcore_emac.c
@@ -0,0 +1,391 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ethernet MAC driver for the J-Core family of SoCs.
+ * Based on SEI MAC driver by Oleksandr G Zhadan / Smart Energy Instruments Inc.
+ * Copyright (c) 2025 Artur Rojek <contact@artur-rojek.eu>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/etherdevice.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/jiffies.h>
+#include <linux/minmax.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define	JCORE_EMAC_CONTROL		0x0
+#define	JCORE_EMAC_TX_LEN		0x4
+#define	JCORE_EMAC_MACL			0x8
+#define	JCORE_EMAC_MACH			0xc
+#define	JCORE_EMAC_MCAST_MASK(n)	(0x60 + ((n) * 4))
+#define	JCORE_EMAC_RX_BUF		0x1000
+#define	JCORE_EMAC_TX_BUF		0x1800
+
+#define	JCORE_EMAC_ENABLE_RX		BIT(1)
+#define	JCORE_EMAC_BUSY			BIT(2)
+#define	JCORE_EMAC_MCAST		BIT(3)
+#define	JCORE_EMAC_READ			BIT(4)
+#define	JCORE_EMAC_ENABLE_INT_RX	BIT(5)
+#define	JCORE_EMAC_ENABLE_INT_TX	BIT(6)
+#define	JCORE_EMAC_PROMISC		BIT(7)
+#define	JCORE_EMAC_COMPLETE		BIT(8)
+#define	JCORE_EMAC_CRC_ERR		BIT(9)
+#define	JCORE_EMAC_PKT_LEN		GENMASK(26, 16)
+
+#define	JCORE_EMAC_RX_BUFFERS		4
+#define	JCORE_EMAC_TX_TIMEOUT		(2 * USEC_PER_SEC)
+#define	JCORE_EMAC_MCAST_ADDRS		4
+
+struct jcore_emac {
+	void __iomem *base;
+	struct regmap *map;
+	struct net_device *ndev;
+	struct {
+		struct u64_stats_sync syncp;
+		u64 rx_packets;
+		u64 tx_packets;
+		u64 rx_bytes;
+		u64 tx_bytes;
+		u64 rx_dropped;
+		u64 rx_errors;
+		u64 rx_crc_errors;
+	} stats;
+};
+
+static irqreturn_t jcore_emac_irq(int irq, void *data)
+{
+	struct jcore_emac *priv = data;
+	struct net_device *ndev = priv->ndev;
+	struct sk_buff *skb;
+	struct {
+		int packets;
+		int bytes;
+		int dropped;
+		int crc_errors;
+	} stats = {};
+	unsigned int status, pkt_len, i;
+
+	for (i = 0; i < JCORE_EMAC_RX_BUFFERS; i++) {
+		regmap_read(priv->map, JCORE_EMAC_CONTROL, &status);
+
+		if (!(status & JCORE_EMAC_COMPLETE))
+			break;
+
+		/* Handle the next RX ping-pong buffer. */
+		if (status & JCORE_EMAC_CRC_ERR) {
+			stats.dropped++;
+			stats.crc_errors++;
+			goto next;
+		}
+
+		skb = netdev_alloc_skb_ip_align(ndev, ndev->mtu +
+						ETH_HLEN + ETH_FCS_LEN);
+		if (!skb) {
+			stats.dropped++;
+			goto next;
+		}
+
+		pkt_len = FIELD_GET(JCORE_EMAC_PKT_LEN, status);
+		skb_put(skb, pkt_len);
+
+		memcpy_fromio(skb->data, priv->base + JCORE_EMAC_RX_BUF,
+			      pkt_len);
+		skb->dev = ndev;
+		skb->protocol = eth_type_trans(skb, ndev);
+
+		stats.packets++;
+		stats.bytes += pkt_len;
+
+		netif_rx(skb);
+
+next:
+		regmap_set_bits(priv->map, JCORE_EMAC_CONTROL, JCORE_EMAC_READ);
+	}
+
+	u64_stats_update_begin(&priv->stats.syncp);
+	priv->stats.rx_packets += stats.packets;
+	priv->stats.rx_bytes += stats.bytes;
+	priv->stats.rx_dropped += stats.dropped;
+	priv->stats.rx_crc_errors += stats.crc_errors;
+	priv->stats.rx_errors += stats.crc_errors;
+	u64_stats_update_end(&priv->stats.syncp);
+
+	return IRQ_HANDLED;
+}
+
+static int jcore_emac_wait(struct jcore_emac *priv)
+{
+	unsigned int val;
+
+	return regmap_read_poll_timeout(priv->map, JCORE_EMAC_CONTROL, val,
+					!(val & JCORE_EMAC_BUSY),
+					100, JCORE_EMAC_TX_TIMEOUT);
+}
+
+static void jcore_emac_reset(struct jcore_emac *priv)
+{
+	regmap_write(priv->map, JCORE_EMAC_CONTROL, 0);
+	usleep_range(10, 20);
+}
+
+static int jcore_emac_open(struct net_device *ndev)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+
+	if (jcore_emac_wait(priv))
+		return -ETIMEDOUT;
+
+	jcore_emac_reset(priv);
+	regmap_set_bits(priv->map, JCORE_EMAC_CONTROL,
+			JCORE_EMAC_ENABLE_RX | JCORE_EMAC_ENABLE_INT_RX |
+			JCORE_EMAC_READ);
+	regmap_clear_bits(priv->map, JCORE_EMAC_CONTROL, JCORE_EMAC_BUSY);
+
+	netif_start_queue(ndev);
+	netif_carrier_on(ndev);
+
+	return 0;
+}
+
+static int jcore_emac_close(struct net_device *ndev)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+
+	netif_stop_queue(ndev);
+	netif_carrier_off(ndev);
+
+	if (jcore_emac_wait(priv))
+		return -ETIMEDOUT;
+
+	jcore_emac_reset(priv);
+
+	return 0;
+}
+
+static int jcore_emac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+	unsigned int tx_len;
+
+	if (jcore_emac_wait(priv))
+		return NETDEV_TX_BUSY;
+
+	memcpy_toio(priv->base + JCORE_EMAC_TX_BUF, skb->data, skb->len);
+
+	tx_len = max(skb->len, 60);
+	regmap_write(priv->map, JCORE_EMAC_TX_LEN, tx_len);
+	regmap_set_bits(priv->map, JCORE_EMAC_CONTROL, JCORE_EMAC_BUSY);
+
+	u64_stats_update_begin(&priv->stats.syncp);
+	priv->stats.tx_packets++;
+	priv->stats.tx_bytes += skb->len;
+	u64_stats_update_end(&priv->stats.syncp);
+
+	consume_skb(skb);
+
+	return NETDEV_TX_OK;
+}
+
+static void jcore_emac_set_rx_mode(struct net_device *ndev)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+	struct netdev_hw_addr *ha;
+	unsigned int reg, i, idx = 0, set_mask = 0, clear_mask = 0, addr = 0;
+
+	if (ndev->flags & IFF_PROMISC)
+		set_mask |= JCORE_EMAC_PROMISC;
+	else
+		clear_mask |= JCORE_EMAC_PROMISC;
+
+	if (ndev->flags & IFF_ALLMULTI)
+		set_mask |= JCORE_EMAC_MCAST;
+	else
+		clear_mask |= JCORE_EMAC_MCAST;
+
+	regmap_update_bits(priv->map, JCORE_EMAC_CONTROL, set_mask | clear_mask,
+			   set_mask);
+
+	if (!(ndev->flags & IFF_MULTICAST))
+		return;
+
+	netdev_for_each_mc_addr(ha, ndev) {
+		/* Only the first 3 octets are used in a hardware mcast mask. */
+		memcpy(&addr, ha->addr, 3);
+
+		for (i = 0; i < idx; i++) {
+			regmap_read(priv->map, JCORE_EMAC_MCAST_MASK(i), &reg);
+			if (reg == addr)
+				goto next_ha;
+		}
+
+		regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(idx), addr);
+		if (++idx >= JCORE_EMAC_MCAST_ADDRS) {
+			netdev_warn(ndev, "Multicast list limit reached\n");
+			break;
+		}
+next_ha:
+	}
+
+	/* Clear the remaining mask entries. */
+	for (i = idx; i < JCORE_EMAC_MCAST_ADDRS; i++)
+		regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(i), 0);
+}
+
+static void jcore_emac_read_hw_addr(struct jcore_emac *priv, u8 *addr)
+{
+	unsigned int val;
+
+	regmap_read(priv->map, JCORE_EMAC_MACL, &val);
+	addr[5] = val;
+	addr[4] = val >> 8;
+	addr[3] = val >> 16;
+	addr[2] = val >> 24;
+	regmap_read(priv->map, JCORE_EMAC_MACH, &val);
+	addr[1] = val;
+	addr[0] = val >> 8;
+}
+
+static void jcore_emac_write_hw_addr(struct jcore_emac *priv, u8 *addr)
+{
+	unsigned int val;
+
+	val = addr[0] << 8 | addr[1];
+	regmap_write(priv->map, JCORE_EMAC_MACH, val);
+
+	val = addr[2] << 24 | addr[3] << 16 | addr[4] << 8 | addr[5];
+	regmap_write(priv->map, JCORE_EMAC_MACL, val);
+}
+
+static int jcore_emac_set_mac_address(struct net_device *ndev, void *addr)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+	struct sockaddr *sa = addr;
+	int ret;
+
+	ret = eth_prepare_mac_addr_change(ndev, addr);
+	if (ret)
+		return ret;
+
+	jcore_emac_write_hw_addr(priv, sa->sa_data);
+	eth_hw_addr_set(ndev, sa->sa_data);
+
+	return 0;
+}
+
+static void jcore_emac_get_stats64(struct net_device *ndev,
+				   struct rtnl_link_stats64 *stats)
+{
+	struct jcore_emac *priv = netdev_priv(ndev);
+	unsigned int start;
+
+	do {
+		start = u64_stats_fetch_begin(&priv->stats.syncp);
+		stats->rx_packets = priv->stats.rx_packets;
+		stats->tx_packets = priv->stats.tx_packets;
+		stats->rx_bytes = priv->stats.rx_bytes;
+		stats->tx_bytes = priv->stats.tx_bytes;
+		stats->rx_dropped = priv->stats.rx_dropped;
+		stats->rx_errors = priv->stats.rx_errors;
+		stats->rx_crc_errors = priv->stats.rx_crc_errors;
+	} while (u64_stats_fetch_retry(&priv->stats.syncp, start));
+}
+
+static const struct net_device_ops jcore_emac_netdev_ops = {
+	.ndo_open = jcore_emac_open,
+	.ndo_stop = jcore_emac_close,
+	.ndo_start_xmit = jcore_emac_start_xmit,
+	.ndo_set_rx_mode = jcore_emac_set_rx_mode,
+	.ndo_set_mac_address = jcore_emac_set_mac_address,
+	.ndo_get_stats64 = jcore_emac_get_stats64,
+};
+
+static const struct regmap_config jcore_emac_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.max_register = JCORE_EMAC_MCAST_MASK(3),
+	.fast_io = true, /* Force spinlock for JCORE_EMAC_CONTROL ISR access. */
+};
+
+static int jcore_emac_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct jcore_emac *priv;
+	struct net_device *ndev;
+	u8 mac[ETH_ALEN];
+	unsigned int i;
+	int irq, ret;
+
+	ndev = devm_alloc_etherdev(dev, sizeof(*priv));
+	if (!ndev)
+		return -ENOMEM;
+
+	SET_NETDEV_DEV(ndev, dev);
+
+	priv = netdev_priv(ndev);
+	priv->ndev = ndev;
+
+	priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->map = devm_regmap_init_mmio(dev, priv->base,
+					  &jcore_emac_regmap_cfg);
+	if (IS_ERR(priv->map))
+		return PTR_ERR(priv->map);
+
+	platform_set_drvdata(pdev, ndev);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_irq(dev, irq, jcore_emac_irq, 0, dev_name(dev),
+			       priv);
+	if (ret < 0)
+		return ret;
+
+	ndev->watchdog_timeo = usecs_to_jiffies(JCORE_EMAC_TX_TIMEOUT);
+	ndev->netdev_ops = &jcore_emac_netdev_ops;
+
+	/* Put hardware into a known state. */
+	jcore_emac_reset(priv);
+	for (i = 0; i < JCORE_EMAC_MCAST_ADDRS; i++)
+		regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(i), 0);
+
+	jcore_emac_read_hw_addr(priv, mac);
+	if (is_zero_ether_addr(mac)) {
+		eth_random_addr(mac);
+		jcore_emac_write_hw_addr(priv, mac);
+	}
+	eth_hw_addr_set(ndev, mac);
+
+	ret = devm_register_netdev(dev, ndev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Unable to register netdev\n");
+
+	return 0;
+}
+
+static const struct of_device_id jcore_emac_of_match[] = {
+	{ .compatible = "jcore,emac", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, jcore_emac_of_match);
+
+static struct platform_driver jcore_emac_driver = {
+	.driver = {
+		.name = "jcore-emac",
+		.of_match_table = jcore_emac_of_match,
+	},
+	.probe = jcore_emac_probe,
+};
+
+module_platform_driver(jcore_emac_driver);
+MODULE_DESCRIPTION("Ethernet MAC driver for the J-Core family of SoCs");
+MODULE_AUTHOR("Artur Rojek <contact@artur-rojek.eu>");
+MODULE_LICENSE("GPL");
-- 
2.50.1

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

> +static irqreturn_t jcore_emac_irq(int irq, void *data)
> +{
> +	struct jcore_emac *priv = data;
> +	struct net_device *ndev = priv->ndev;
> +	struct sk_buff *skb;
> +	struct {
> +		int packets;
> +		int bytes;
> +		int dropped;
> +		int crc_errors;
> +	} stats = {};
> +	unsigned int status, pkt_len, i;

netdev uses 'reverse christmas tree' for local variables. They should
be sorted longest to shortest. This sometimes means you need to move
assignments into the body of the function, in this case, ndev.

> +	jcore_emac_read_hw_addr(priv, mac);
> +	if (is_zero_ether_addr(mac)) {

It would be more normal to use !is_valid_ether_addr()

What support is there for MDIO? Normally the MAC driver would not be
setting the carrier status, phylink or phylib would do that.

    Andrew

---
pw-bot: cr

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-15 22:16, Andrew Lunn wrote:

Hi Andrew,
thanks for the review!

>> +static irqreturn_t jcore_emac_irq(int irq, void *data)
>> +{
>> +	struct jcore_emac *priv = data;
>> +	struct net_device *ndev = priv->ndev;
>> +	struct sk_buff *skb;
>> +	struct {
>> +		int packets;
>> +		int bytes;
>> +		int dropped;
>> +		int crc_errors;
>> +	} stats = {};
>> +	unsigned int status, pkt_len, i;
> 
> netdev uses 'reverse christmas tree' for local variables. They should
> be sorted longest to shortest. This sometimes means you need to move
> assignments into the body of the function, in this case, ndev.
> 
>> +	jcore_emac_read_hw_addr(priv, mac);
>> +	if (is_zero_ether_addr(mac)) {
> 
> It would be more normal to use !is_valid_ether_addr()
> 
> What support is there for MDIO? Normally the MAC driver would not be
> setting the carrier status, phylink or phylib would do that.

 From what I can tell, none. This is a very simple FPGA RTL
implementation of a MAC, and looking at the VHDL, I don't see any MDIO
registers. Moreover, the MDIO pin on the PHY IC on my dev board also
appears unconnected. Perhaps Rob L. or Jeff can shine more light on this
design wise.

Cheers,
Artur

> 
>     Andrew
> 
> ---
> pw-bot: cr

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-15 22:52, Artur Rojek wrote:
> On 2025-08-15 22:16, Andrew Lunn wrote:
> 
> Hi Andrew,
> thanks for the review!
> 
>>> +static irqreturn_t jcore_emac_irq(int irq, void *data)
>>> +{
>>> +	struct jcore_emac *priv = data;
>>> +	struct net_device *ndev = priv->ndev;
>>> +	struct sk_buff *skb;
>>> +	struct {
>>> +		int packets;
>>> +		int bytes;
>>> +		int dropped;
>>> +		int crc_errors;
>>> +	} stats = {};
>>> +	unsigned int status, pkt_len, i;
>> 
>> netdev uses 'reverse christmas tree' for local variables. They should
>> be sorted longest to shortest. This sometimes means you need to move
>> assignments into the body of the function, in this case, ndev.

Should I move the struct stats members into stand alone variables as
well? Or is below sorting acceptable with regards to stats vs skb:

> 	unsigned int status, pkt_len, i;
> 	struct jcore_emac *priv = data;
> 	struct net_device *ndev;
> 	struct {
> 		int crc_errors;
> 		int dropped;
> 		int packets;
> 		int bytes;
> 	} stats = {};
> 	struct sk_buff *skb;

>> 
>>> +	jcore_emac_read_hw_addr(priv, mac);
>>> +	if (is_zero_ether_addr(mac)) {
>> 
>> It would be more normal to use !is_valid_ether_addr()
>> 
>> What support is there for MDIO? Normally the MAC driver would not be
>> setting the carrier status, phylink or phylib would do that.
> 
> From what I can tell, none. This is a very simple FPGA RTL
> implementation of a MAC, and looking at the VHDL, I don't see any MDIO
> registers.

> Moreover, the MDIO pin on the PHY IC on my dev board also
> appears unconnected.

I spoke too soon on that one. It appears to be connected through a trace
that goes under the IC. Nevertheless, I don't think MDIO support is in
the IP core design.

> Perhaps Rob L. or Jeff can shine more light on this
> design wise.
> 
> Cheers,
> Artur
> 
>> 
>>     Andrew
>> 
>> ---
>> pw-bot: cr

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

On Fri, Aug 15, 2025 at 11:14:08PM +0200, Artur Rojek wrote:
> On 2025-08-15 22:52, Artur Rojek wrote:
> > On 2025-08-15 22:16, Andrew Lunn wrote:
> > 
> > Hi Andrew,
> > thanks for the review!
> > 
> > > > +static irqreturn_t jcore_emac_irq(int irq, void *data)
> > > > +{
> > > > +	struct jcore_emac *priv = data;
> > > > +	struct net_device *ndev = priv->ndev;
> > > > +	struct sk_buff *skb;
> > > > +	struct {
> > > > +		int packets;
> > > > +		int bytes;
> > > > +		int dropped;
> > > > +		int crc_errors;
> > > > +	} stats = {};
> > > > +	unsigned int status, pkt_len, i;
> > > 
> > > netdev uses 'reverse christmas tree' for local variables. They should
> > > be sorted longest to shortest. This sometimes means you need to move
> > > assignments into the body of the function, in this case, ndev.
> 
> Should I move the struct stats members into stand alone variables as
> well? Or is below sorting acceptable with regards to stats vs skb:

I would pull the structure definition out of the function. Then just
create one instance of the structure on the stack.

> > > What support is there for MDIO? Normally the MAC driver would not be
> > > setting the carrier status, phylink or phylib would do that.
> > 
> > From what I can tell, none. This is a very simple FPGA RTL
> > implementation of a MAC, and looking at the VHDL, I don't see any MDIO
> > registers.
> 
> > Moreover, the MDIO pin on the PHY IC on my dev board also
> > appears unconnected.
> 
> I spoke too soon on that one. It appears to be connected through a trace
> that goes under the IC. Nevertheless, I don't think MDIO support is in
> the IP core design.

MDIO is actually two pins. MDC and MDIO.

It might be there is a second IP core which implements MDIO. There is
no reason it needs to be tightly integrated into the MAC. But it does
make the MAC driver slightly more complex. You then need a Linux MDIO
bus driver for it, and the DT for the MAC would include a phy-handle
property pointing to the PHY on the MDIO bus.

Is there an Ethernet PHY on your board?

	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-16 00:38, Andrew Lunn wrote:
> On Fri, Aug 15, 2025 at 11:14:08PM +0200, Artur Rojek wrote:
>> On 2025-08-15 22:52, Artur Rojek wrote:
>> > On 2025-08-15 22:16, Andrew Lunn wrote:
>> >
>> > Hi Andrew,
>> > thanks for the review!
>> >
>> > > > +static irqreturn_t jcore_emac_irq(int irq, void *data)
>> > > > +{
>> > > > +	struct jcore_emac *priv = data;
>> > > > +	struct net_device *ndev = priv->ndev;
>> > > > +	struct sk_buff *skb;
>> > > > +	struct {
>> > > > +		int packets;
>> > > > +		int bytes;
>> > > > +		int dropped;
>> > > > +		int crc_errors;
>> > > > +	} stats = {};
>> > > > +	unsigned int status, pkt_len, i;
>> > >
>> > > netdev uses 'reverse christmas tree' for local variables. They should
>> > > be sorted longest to shortest. This sometimes means you need to move
>> > > assignments into the body of the function, in this case, ndev.
>> 
>> Should I move the struct stats members into stand alone variables as
>> well? Or is below sorting acceptable with regards to stats vs skb:
> 
> I would pull the structure definition out of the function. Then just
> create one instance of the structure on the stack.

Makes sense, thanks.

> 
>> > > What support is there for MDIO? Normally the MAC driver would not be
>> > > setting the carrier status, phylink or phylib would do that.
>> >
>> > From what I can tell, none. This is a very simple FPGA RTL
>> > implementation of a MAC, and looking at the VHDL, I don't see any MDIO
>> > registers.
>> 
>> > Moreover, the MDIO pin on the PHY IC on my dev board also
>> > appears unconnected.
>> 
>> I spoke too soon on that one. It appears to be connected through a 
>> trace
>> that goes under the IC. Nevertheless, I don't think MDIO support is in
>> the IP core design.
> 
> MDIO is actually two pins. MDC and MDIO.
> 
> It might be there is a second IP core which implements MDIO. There is
> no reason it needs to be tightly integrated into the MAC. But it does
> make the MAC driver slightly more complex. You then need a Linux MDIO
> bus driver for it, and the DT for the MAC would include a phy-handle
> property pointing to the PHY on the MDIO bus.
> 
> Is there an Ethernet PHY on your board?

Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both MDC
and MDIO pins connected, however I suspect that nothing really
configures it, and it simply runs on default register values (which
allow for valid operation in 100Mb/s mode, it seems). I doubt there is
another IP core to handle MDIO, as this SoC design is optimized for
minimal utilization of FPGA blocks. Does it make sense to you that a MAC
could run without any access to an MDIO bus?

If neither Rob L. or Jeff clarify on this topic, I'll hook up a logic
analyzer to the MDIO bus and see if anything (e.g. loader firmware)
touches it at any point.

Cheers,
Artur

[1] https://www.micros.com.pl/mediaserver/info-uiip101a.pdf

> 
> 	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Stephen Hemminger]

On Fri, 15 Aug 2025 21:48:06 +0200
Artur Rojek <contact@artur-rojek.eu> wrote:

> +	struct {
> +		int packets;
> +		int bytes;
> +		int dropped;
> +		int crc_errors;
> +	} stats = {};

You don't want signed integer here.
Probably u32 or u64.

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

> Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both MDC
> and MDIO pins connected, however I suspect that nothing really
> configures it, and it simply runs on default register values (which
> allow for valid operation in 100Mb/s mode, it seems). I doubt there is
> another IP core to handle MDIO, as this SoC design is optimized for
> minimal utilization of FPGA blocks. Does it make sense to you that a MAC
> could run without any access to an MDIO bus?

It can work like that. You will likely have problems if the link ever
negotiates 10Mbps or 100Mbps half duplex. You generally need to change
something in the MAC to support different speeds and duplex. Without
being able to talk to the PHY over MDIO you have no idea what it has
negotiated with the link peer.

	Andrew

Re: [PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Krzysztof Kozlowski]

On 15/08/2025 21:48, Artur Rojek wrote:
> J-Core is a clean-room open source processor and SoC design using the
> SuperH instruction set.
> 
> The 'jcore' prefix is in use by IP cores originating from this design.
> 
> Link: https://j-core.org
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

How is it possible if this is v1? If this is not v1, where is changelog
and why isn't it marked as vx?

> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
> ---
>  Documentation/devicetree/bindings/vendor-prefixes.yaml | 2 ++
>  1 file changed, 2 insertions(+)
Best regards,
Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Krzysztof Kozlowski]

On 15/08/2025 21:48, Artur Rojek wrote:
> Add a documentation file to describe the Device Tree bindings for the
> Ethernet Media Access Controller found in the J-Core family of SoCs.
> 
> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
> ---
>  .../devicetree/bindings/net/jcore,emac.yaml   | 42 +++++++++++++++++++
>  1 file changed, 42 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/jcore,emac.yaml
> 
> diff --git a/Documentation/devicetree/bindings/net/jcore,emac.yaml b/Documentation/devicetree/bindings/net/jcore,emac.yaml
> new file mode 100644
> index 000000000000..a4384f7ed83d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/jcore,emac.yaml
> @@ -0,0 +1,42 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/net/jcore,emac.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: J-Core Ethernet Media Access Controller
> +
> +description: |
> +  This node provides properties for configuring the Ethernet MAC found
> +  in the J-Core family of SoCs.
> +
> +maintainers:
> +  - Artur Rojek <contact@artur-rojek.eu>
> +
> +properties:
> +  compatible:
> +    const: jcore,emac

You need SoC-based compatibles. And then also rename the file to match it.

> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +
> +allOf:
> +  - $ref: ethernet-controller.yaml#
> +
> +additionalProperties: false

unevaluatedProperties instead

> +
> +examples:
> +  - |
> +    ethernet@10000 {
> +      compatible = "jcore,emac";
> +      reg = <0x10000 0x2000>;
> +      interrupts = <0x11>;

That's not hex...

> +    };


Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Geert Uytterhoeven]

Hi Krzysztof,

On Sat, 16 Aug 2025 at 10:18, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> On 15/08/2025 21:48, Artur Rojek wrote:
> > J-Core is a clean-room open source processor and SoC design using the
> > SuperH instruction set.
> >
> > The 'jcore' prefix is in use by IP cores originating from this design.
> >
> > Link: https://j-core.org
> > Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
>
> How is it possible if this is v1? If this is not v1, where is changelog
> and why isn't it marked as vx?

The patch series had several iterations (v0, v-1, v-2 ;-), with a limited
audience.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Krzysztof Kozlowski]

On 16/08/2025 10:22, Geert Uytterhoeven wrote:
> Hi Krzysztof,
> 
> On Sat, 16 Aug 2025 at 10:18, Krzysztof Kozlowski <krzk@kernel.org> wrote:
>> On 15/08/2025 21:48, Artur Rojek wrote:
>>> J-Core is a clean-room open source processor and SoC design using the
>>> SuperH instruction set.
>>>
>>> The 'jcore' prefix is in use by IP cores originating from this design.
>>>
>>> Link: https://j-core.org
>>> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
>>
>> How is it possible if this is v1? If this is not v1, where is changelog
>> and why isn't it marked as vx?
> 
> The patch series had several iterations (v0, v-1, v-2 ;-), with a limited
> audience.

Thanks, would be nice to see it reflected somewhere.

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Krzysztof Kozlowski]

On 15/08/2025 21:48, Artur Rojek wrote:
> J-Core is a clean-room open source processor and SoC design using the
> SuperH instruction set.
> 
> The 'jcore' prefix is in use by IP cores originating from this design.
> 
> Link: https://j-core.org
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: vendor-prefixes: Document J-Core

[Artur Rojek]

On 2025-08-16 11:40, Krzysztof Kozlowski wrote:
> On 16/08/2025 10:22, Geert Uytterhoeven wrote:
>> Hi Krzysztof,

Hi Krzysztof,
thanks for the review!

>> 
>> On Sat, 16 Aug 2025 at 10:18, Krzysztof Kozlowski <krzk@kernel.org> 
>> wrote:
>>> On 15/08/2025 21:48, Artur Rojek wrote:
>>>> J-Core is a clean-room open source processor and SoC design using 
>>>> the
>>>> SuperH instruction set.
>>>> 
>>>> The 'jcore' prefix is in use by IP cores originating from this 
>>>> design.
>>>> 
>>>> Link: https://j-core.org
>>>> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
>>> 
>>> How is it possible if this is v1? If this is not v1, where is 
>>> changelog
>>> and why isn't it marked as vx?
>> 
>> The patch series had several iterations (v0, v-1, v-2 ;-), with a 
>> limited
>> audience.
> 
> Thanks, would be nice to see it reflected somewhere.

I mentioned it in the cover letter.

For the record:
v1: capitalize Open Processor
v0: new patch

Cheers,
Artur

> 
> Best regards,
> Krzysztof

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[kernel test robot]

Hi Artur,

kernel test robot noticed the following build warnings:

[auto build test WARNING on robh/for-next]
[also build test WARNING on linus/master v6.17-rc1 next-20250815]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Artur-Rojek/dt-bindings-vendor-prefixes-Document-J-Core/20250816-042354
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20250815194806.1202589-4-contact%40artur-rojek.eu
patch subject: [PATCH 3/3] net: j2: Introduce J-Core EMAC
config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20250816/202508161930.ergOga3z-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250816/202508161930.ergOga3z-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508161930.ergOga3z-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/net/ethernet/jcore_emac.c:231:2: warning: label at end of compound statement is a C2x extension [-Wc2x-extensions]
     231 |         }
         |         ^
   1 warning generated.


vim +231 drivers/net/ethernet/jcore_emac.c

   192	
   193	static void jcore_emac_set_rx_mode(struct net_device *ndev)
   194	{
   195		struct jcore_emac *priv = netdev_priv(ndev);
   196		struct netdev_hw_addr *ha;
   197		unsigned int reg, i, idx = 0, set_mask = 0, clear_mask = 0, addr = 0;
   198	
   199		if (ndev->flags & IFF_PROMISC)
   200			set_mask |= JCORE_EMAC_PROMISC;
   201		else
   202			clear_mask |= JCORE_EMAC_PROMISC;
   203	
   204		if (ndev->flags & IFF_ALLMULTI)
   205			set_mask |= JCORE_EMAC_MCAST;
   206		else
   207			clear_mask |= JCORE_EMAC_MCAST;
   208	
   209		regmap_update_bits(priv->map, JCORE_EMAC_CONTROL, set_mask | clear_mask,
   210				   set_mask);
   211	
   212		if (!(ndev->flags & IFF_MULTICAST))
   213			return;
   214	
   215		netdev_for_each_mc_addr(ha, ndev) {
   216			/* Only the first 3 octets are used in a hardware mcast mask. */
   217			memcpy(&addr, ha->addr, 3);
   218	
   219			for (i = 0; i < idx; i++) {
   220				regmap_read(priv->map, JCORE_EMAC_MCAST_MASK(i), &reg);
   221				if (reg == addr)
   222					goto next_ha;
   223			}
   224	
   225			regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(idx), addr);
   226			if (++idx >= JCORE_EMAC_MCAST_ADDRS) {
   227				netdev_warn(ndev, "Multicast list limit reached\n");
   228				break;
   229			}
   230	next_ha:
 > 231		}
   232	
   233		/* Clear the remaining mask entries. */
   234		for (i = idx; i < JCORE_EMAC_MCAST_ADDRS; i++)
   235			regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(i), 0);
   236	}
   237	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Artur Rojek]

On 2025-08-16 10:19, Krzysztof Kozlowski wrote:
> On 15/08/2025 21:48, Artur Rojek wrote:
>> Add a documentation file to describe the Device Tree bindings for the
>> Ethernet Media Access Controller found in the J-Core family of SoCs.
>> 
>> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
>> ---
>>  .../devicetree/bindings/net/jcore,emac.yaml   | 42 
>> +++++++++++++++++++
>>  1 file changed, 42 insertions(+)
>>  create mode 100644 
>> Documentation/devicetree/bindings/net/jcore,emac.yaml
>> 
>> diff --git a/Documentation/devicetree/bindings/net/jcore,emac.yaml 
>> b/Documentation/devicetree/bindings/net/jcore,emac.yaml
>> new file mode 100644
>> index 000000000000..a4384f7ed83d
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/net/jcore,emac.yaml
>> @@ -0,0 +1,42 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/net/jcore,emac.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: J-Core Ethernet Media Access Controller
>> +
>> +description: |
>> +  This node provides properties for configuring the Ethernet MAC 
>> found
>> +  in the J-Core family of SoCs.
>> +
>> +maintainers:
>> +  - Artur Rojek <contact@artur-rojek.eu>
>> +
>> +properties:
>> +  compatible:
>> +    const: jcore,emac
> 
> You need SoC-based compatibles. And then also rename the file to match 
> it.

Given how the top-most compatible of the bindings [1] of the board I am
using has "jcore,j2-soc", this driver should probably go with
"jcore,j2-emac".

But as this is an FPGA design, I don't know how widespread the use is
across other jcore derived SoCs (if any?).
I will wait for Jeff (who's design this is) to clarify on that.

PS. Too bad we already have other IP cores following the old pattern:

> $ grep -r "compatible = \"jcore," bindings/ | grep -v "emac"
> bindings/timer/jcore,pit.yaml:        compatible = "jcore,pit";
> bindings/spi/jcore,spi.txt:	compatible = "jcore,spi2";
> bindings/interrupt-controller/jcore,aic.yaml:        compatible = 
> "jcore,aic2";

Cheers,
Artur

[1] 
https://raw.githubusercontent.com/j-core/jcore-soc/refs/heads/master/targets/boards/turtle_1v1/board.dts

> 
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - interrupts
>> +
>> +allOf:
>> +  - $ref: ethernet-controller.yaml#
>> +
>> +additionalProperties: false
> 
> unevaluatedProperties instead
> 
>> +
>> +examples:
>> +  - |
>> +    ethernet@10000 {
>> +      compatible = "jcore,emac";
>> +      reg = <0x10000 0x2000>;
>> +      interrupts = <0x11>;
> 
> That's not hex...
> 
>> +    };
> 
> 
> Best regards,
> Krzysztof

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-16 02:18, Andrew Lunn wrote:
>> Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both 
>> MDC
>> and MDIO pins connected, however I suspect that nothing really
>> configures it, and it simply runs on default register values (which
>> allow for valid operation in 100Mb/s mode, it seems). I doubt there is
>> another IP core to handle MDIO, as this SoC design is optimized for
>> minimal utilization of FPGA blocks. Does it make sense to you that a 
>> MAC
>> could run without any access to an MDIO bus?
> 
> It can work like that. You will likely have problems if the link ever
> negotiates 10Mbps or 100Mbps half duplex. You generally need to change
> something in the MAC to support different speeds and duplex. Without
> being able to talk to the PHY over MDIO you have no idea what it has
> negotiated with the link peer.

Thanks for the explanation. I just confirmed that there is no activity
on the MDIO bus from board power on, up to the jcore_emac driver start
(and past it), so most likely this SoC design does not provide any
management interface between MAC and PHY. I guess once/if MDIO is
implemented, we can distinguish between IP core revision compatibles,
and properly switch between netif_carrier_*()/phylink logic.

Cheers,
Artur

> 
> 	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

On Sat, Aug 16, 2025 at 03:40:57PM +0200, Artur Rojek wrote:
> On 2025-08-16 02:18, Andrew Lunn wrote:
> > > Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both
> > > MDC
> > > and MDIO pins connected, however I suspect that nothing really
> > > configures it, and it simply runs on default register values (which
> > > allow for valid operation in 100Mb/s mode, it seems). I doubt there is
> > > another IP core to handle MDIO, as this SoC design is optimized for
> > > minimal utilization of FPGA blocks. Does it make sense to you that a
> > > MAC
> > > could run without any access to an MDIO bus?
> > 
> > It can work like that. You will likely have problems if the link ever
> > negotiates 10Mbps or 100Mbps half duplex. You generally need to change
> > something in the MAC to support different speeds and duplex. Without
> > being able to talk to the PHY over MDIO you have no idea what it has
> > negotiated with the link peer.
> 
> Thanks for the explanation. I just confirmed that there is no activity
> on the MDIO bus from board power on, up to the jcore_emac driver start
> (and past it), so most likely this SoC design does not provide any
> management interface between MAC and PHY. I guess once/if MDIO is
> implemented, we can distinguish between IP core revision compatibles,
> and properly switch between netif_carrier_*()/phylink logic.

How cut down of a SoC design is it? Is there pinmux and each pin can
also be used for GPIO? Linux has software bit-banging MDIO, if you can
make the two pins be standard Linux GPIOs, and can configure them
correctly, i _think_ open drain on MDIO. It will be slow, but it
works, and it is pretty much for free.

MDIO itself is simple, just a big shift register:

https://opencores.org/websvn/filedetails?repname=ethmac10g&path=%2Fethmac10g%2Ftrunk%2Frtl%2Fverilog%2Fmgmt%2Fmdio.v

	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[D. Jeff Dionne]

On Aug 16, 2025, at 22:40, Artur Rojek <contact@artur-rojek.eu> wrote:

The MDIO isn’t implemented yet.  There is a pin driver for it, but it relies on
pin strapping the Phy.  Probably because all the designs that SoC base is in
(IIRC 10 or so customer and prototype designs, plus Turtle and a few 
derivatives), the SoC was designed in conjunction with board.  A bit lazy.

But they all have the MDIO connected, so we should add it (it’s very simple).

Cheers,
J.

> On 2025-08-16 02:18, Andrew Lunn wrote:
>>> Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both MDC
>>> and MDIO pins connected, however I suspect that nothing really
>>> configures it, and it simply runs on default register values (which
>>> allow for valid operation in 100Mb/s mode, it seems). I doubt there is
>>> another IP core to handle MDIO, as this SoC design is optimized for
>>> minimal utilization of FPGA blocks. Does it make sense to you that a MAC
>>> could run without any access to an MDIO bus?
>> It can work like that. You will likely have problems if the link ever
>> negotiates 10Mbps or 100Mbps half duplex. You generally need to change
>> something in the MAC to support different speeds and duplex. Without
>> being able to talk to the PHY over MDIO you have no idea what it has
>> negotiated with the link peer.
> 
> Thanks for the explanation. I just confirmed that there is no activity
> on the MDIO bus from board power on, up to the jcore_emac driver start
> (and past it), so most likely this SoC design does not provide any
> management interface between MAC and PHY. I guess once/if MDIO is
> implemented, we can distinguish between IP core revision compatibles,
> and properly switch between netif_carrier_*()/phylink logic.
> 
> Cheers,
> Artur
> 
>> Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-17 06:29, D. Jeff Dionne wrote:
> On Aug 16, 2025, at 22:40, Artur Rojek <contact@artur-rojek.eu> wrote:
> 
> The MDIO isn’t implemented yet.  There is a pin driver for it, but it 
> relies on
> pin strapping the Phy.  Probably because all the designs that SoC base 
> is in
> (IIRC 10 or so customer and prototype designs, plus Turtle and a few
> derivatives), the SoC was designed in conjunction with board.  A bit 
> lazy.
> 
> But they all have the MDIO connected, so we should add it (it’s very 
> simple).

Hi Jeff,
thanks for the elaboration. It sounds to me then that I should wait with
the driver upstream until the MDIO interface is implemented.

At least I gave you guys a little bit of a nudge :-)

Cheers,
Artur

> 
> Cheers,
> J.
> 
>> On 2025-08-16 02:18, Andrew Lunn wrote:
>>>> Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both 
>>>> MDC
>>>> and MDIO pins connected, however I suspect that nothing really
>>>> configures it, and it simply runs on default register values (which
>>>> allow for valid operation in 100Mb/s mode, it seems). I doubt there 
>>>> is
>>>> another IP core to handle MDIO, as this SoC design is optimized for
>>>> minimal utilization of FPGA blocks. Does it make sense to you that a 
>>>> MAC
>>>> could run without any access to an MDIO bus?
>>> It can work like that. You will likely have problems if the link ever
>>> negotiates 10Mbps or 100Mbps half duplex. You generally need to 
>>> change
>>> something in the MAC to support different speeds and duplex. Without
>>> being able to talk to the PHY over MDIO you have no idea what it has
>>> negotiated with the link peer.
>> 
>> Thanks for the explanation. I just confirmed that there is no activity
>> on the MDIO bus from board power on, up to the jcore_emac driver start
>> (and past it), so most likely this SoC design does not provide any
>> management interface between MAC and PHY. I guess once/if MDIO is
>> implemented, we can distinguish between IP core revision compatibles,
>> and properly switch between netif_carrier_*()/phylink logic.
>> 
>> Cheers,
>> Artur
>> 
>>> Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Artur Rojek]

On 2025-08-16 17:04, Andrew Lunn wrote:
> On Sat, Aug 16, 2025 at 03:40:57PM +0200, Artur Rojek wrote:
>> On 2025-08-16 02:18, Andrew Lunn wrote:
>> > > Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both
>> > > MDC
>> > > and MDIO pins connected, however I suspect that nothing really
>> > > configures it, and it simply runs on default register values (which
>> > > allow for valid operation in 100Mb/s mode, it seems). I doubt there is
>> > > another IP core to handle MDIO, as this SoC design is optimized for
>> > > minimal utilization of FPGA blocks. Does it make sense to you that a
>> > > MAC
>> > > could run without any access to an MDIO bus?
>> >
>> > It can work like that. You will likely have problems if the link ever
>> > negotiates 10Mbps or 100Mbps half duplex. You generally need to change
>> > something in the MAC to support different speeds and duplex. Without
>> > being able to talk to the PHY over MDIO you have no idea what it has
>> > negotiated with the link peer.
>> 
>> Thanks for the explanation. I just confirmed that there is no activity
>> on the MDIO bus from board power on, up to the jcore_emac driver start
>> (and past it), so most likely this SoC design does not provide any
>> management interface between MAC and PHY. I guess once/if MDIO is
>> implemented, we can distinguish between IP core revision compatibles,
>> and properly switch between netif_carrier_*()/phylink logic.
> 
> How cut down of a SoC design is it? Is there pinmux and each pin can
> also be used for GPIO?

It's pretty limited - there is no MMU or DMA, for example. There does
appear to be a GPIO controller, however I'm not sure if it is of pinmux
variety (whether pins used by an IP core can be multiplexed to PIO), or
if it has its own pool of general purpose pins, that don't overlap with
PHY. In any case, there is no Linux driver for it (I have interest to
eventually write one), and I don't know if the design for it is even
included in the bitstream on my board.

> Linux has software bit-banging MDIO, if you can
> make the two pins be standard Linux GPIOs, and can configure them
> correctly, i _think_ open drain on MDIO. It will be slow, but it
> works, and it is pretty much for free.

This is a clever idea! It does however sound like Jeff & co. will
eventually add a proper MDIO interface to this MAC. I will halt upstream
of this driver for now and see what happens first (that, or me
experimenting with GPIO). Thanks for the review of this series thus far!

Cheers,
Artur

> 
> MDIO itself is simple, just a big shift register:
> 
> https://opencores.org/websvn/filedetails?repname=ethmac10g&path=%2Fethmac10g%2Ftrunk%2Frtl%2Fverilog%2Fmgmt%2Fmdio.v
> 
> 	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Rob Landley]

On 8/15/25 17:38, Andrew Lunn wrote:
>>>> What support is there for MDIO? Normally the MAC driver would not be
>>>> setting the carrier status, phylink or phylib would do that.
>>>
>>>  From what I can tell, none. This is a very simple FPGA RTL
>>> implementation of a MAC, and looking at the VHDL, I don't see any MDIO
>>> registers.
>>
>>> Moreover, the MDIO pin on the PHY IC on my dev board also
>>> appears unconnected.
>>
>> I spoke too soon on that one. It appears to be connected through a trace
>> that goes under the IC. Nevertheless, I don't think MDIO support is in
>> the IP core design.
> 
> MDIO is actually two pins. MDC and MDIO.

I asked Jeff and he pointed me at 
https://github.com/j-core/jcore-soc/blob/master/targets/boards/turtle_1v1/pad_ring.vhd#L732 
and 
https://github.com/j-core/jcore-soc/blob/master/targets/pins/turtle_1v0.pins 
and said those two pins are "wired to zero".

He also said: "It would only take a few hrs to add MDIO." but there 
basically hasn't been a use case yet.

> It might be there is a second IP core which implements MDIO. There is
> no reason it needs to be tightly integrated into the MAC. But it does
> make the MAC driver slightly more complex. You then need a Linux MDIO
> bus driver for it, and the DT for the MAC would include a phy-handle
> property pointing to the PHY on the MDIO bus.
> 
> Is there an Ethernet PHY on your board?

According to 
https://github.com/j-core/jcore-jx/blob/master/schematic.pdf it's a 
https://www.micros.com.pl/mediaserver/info-uiip101a.pdf

> 	Andrew

Rob

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

On Sun, Aug 17, 2025 at 11:04:36AM -0500, Rob Landley wrote:
> On 8/15/25 17:38, Andrew Lunn wrote:
> > > > > What support is there for MDIO? Normally the MAC driver would not be
> > > > > setting the carrier status, phylink or phylib would do that.
> > > > 
> > > >  From what I can tell, none. This is a very simple FPGA RTL
> > > > implementation of a MAC, and looking at the VHDL, I don't see any MDIO
> > > > registers.
> > > 
> > > > Moreover, the MDIO pin on the PHY IC on my dev board also
> > > > appears unconnected.
> > > 
> > > I spoke too soon on that one. It appears to be connected through a trace
> > > that goes under the IC. Nevertheless, I don't think MDIO support is in
> > > the IP core design.
> > 
> > MDIO is actually two pins. MDC and MDIO.
> 
> I asked Jeff and he pointed me at https://github.com/j-core/jcore-soc/blob/master/targets/boards/turtle_1v1/pad_ring.vhd#L732
> and
> https://github.com/j-core/jcore-soc/blob/master/targets/pins/turtle_1v0.pins
> and said those two pins are "wired to zero".
> 
> He also said: "It would only take a few hrs to add MDIO." but there
> basically hasn't been a use case yet.

Has anybody tried a link peer which only does 10Mbps? Or one which
negotiates 100Mbs half duplex? Does the MAC still work, or is the link
dead? That would be one use case, making the system more robust to
such conditions.

	Andrew

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Rob Landley]

On 8/16/25 10:04, Andrew Lunn wrote:
> On Sat, Aug 16, 2025 at 03:40:57PM +0200, Artur Rojek wrote:
>> On 2025-08-16 02:18, Andrew Lunn wrote:
>>>> Yes, it's an IC+ IP101ALF 10/100 Ethernet PHY [1]. It does have both
>>>> MDC
>>>> and MDIO pins connected, however I suspect that nothing really
>>>> configures it, and it simply runs on default register values (which
>>>> allow for valid operation in 100Mb/s mode, it seems). I doubt there is
>>>> another IP core to handle MDIO, as this SoC design is optimized for
>>>> minimal utilization of FPGA blocks. Does it make sense to you that a
>>>> MAC
>>>> could run without any access to an MDIO bus?
>>>
>>> It can work like that. You will likely have problems if the link ever
>>> negotiates 10Mbps or 100Mbps half duplex. You generally need to change
>>> something in the MAC to support different speeds and duplex. Without
>>> being able to talk to the PHY over MDIO you have no idea what it has
>>> negotiated with the link peer.
>>
>> Thanks for the explanation. I just confirmed that there is no activity
>> on the MDIO bus from board power on, up to the jcore_emac driver start
>> (and past it), so most likely this SoC design does not provide any
>> management interface between MAC and PHY. I guess once/if MDIO is
>> implemented, we can distinguish between IP core revision compatibles,
>> and properly switch between netif_carrier_*()/phylink logic.
> 
> How cut down of a SoC design is it?

The engineers focused on getting projects done for customers implemented 
what they actually needed, and had a todo list for potential future 
development that mostly hasn't come up yet.

(Most of the boards I worked on aren't actually using ethernet, but 
doing their own derived protocol that's electrically isolated and 
includes timing information in each packet. Same RJ45 jack, I think it 
even uses the same transceiver chip, but different protocol and signaling.)

> Is there pinmux and each pin can
> also be used for GPIO? Linux has software bit-banging MDIO, if you can
> make the two pins be standard Linux GPIOs, and can configure them
> correctly, i _think_ open drain on MDIO. It will be slow, but it
> works, and it is pretty much for free.
> 
> MDIO itself is simple, just a big shift register:

My vague recollection is this SOC only implemented full duplex 100baseT 
because they didn't have any hardware lying around that _couldn't_ talk 
to that. So it never needed to downshift to talk to anything they tested 
it against, and there were plenty of desktop switches if we wound up 
needing an adapter in future for some reason. (1995 was a while ago even 
back then.)

The negotiation stuff was slated to be part of implementing gigabit 
ethernet, but 11 megabytes/second is actually pretty decent throughput 
for an individual endpoint so nothing's really needed it yet.

Turtle's FPGA couldn't easily do gigabit anyway: a spartan 6 can handle 
a 50mhz phy interface but 125mhz for gigabit is pushing it. That really 
wants something like Kintex (WAY more expensive, and runs quite hot). 
Even with the SOC in ASIC, a gigabit phy chip is still more expensive 
and consumes more power so needs a reason to use it.

There's been more interest in wifi and bluetooth, which you either get 
as its own chip or in a micro-sdio card because rolling your own 
implementation is a regulatory hellscape of spectrum compliance 
certifications in a zillion different jurisdictions. (Implementing it 
isn't that hard, getting permission to deploy it in a city is hard.) USB 
dongles are also available but consume WAY too much power.

Oh, a few years ago we did a USB 2.0 implementation in a Turtle HAT:

https://www.raspberrypi.com/news/introducing-raspberry-pi-hats/

And implemented a VHDL CDC-ECM ethernet device in the turtle SOC 
bitstream to test it out with, which did 40 megabytes/second sustained 
throughput no problem. (With not so much a "driver" as a quick and dirty 
userspace realtime program marshalling packets in and out of the 
hardware buffers to a TAP device. Both the USB and Ethernet PHY are 
basically parallel to serial converters so their outsides can clock way 
slower than the line speed of the protocol they transceive. The USB 2.0 
one we used ran at 60mhz=3*5*2*2 and the ethernet needs 50mhz=5*5*2 so 
the voltage controlled oscillator could run at 3*5*5*2*2=300mhz and then 
get divided evenly down to drive both, and yes we had it run as a little 
gateway for testing.)

Alas, while CDC-EDM using the reference vendor:device IDs out of the USB 
standards document works fine out of the box on both Linux and MacOS, 
Windows refuses to recognize it because Microsoft demanded a five figure 
license fee from each hardware vendor to get a driver signed. (Lina Kahn 
didn't get around to them before the plutocrats plugged that hole in the 
pressure cooker.)

In an attempt to bypass the bastardry we changed the VHDL to do RNDIS 
instead (microsoft's own admittedly inferior version of CDC-EDM that 
they let you implement using an existing driver), and Greg KH went "my 
turn":

https://fosstodon.org/@kernellogger/109397395514594409

Which of course broke Android USB tethering.

*shrug* The 100baseT one works for us.

Rob

P.S. Way back when, we did slap quick wifi on an existing design once as 
a proof of concept using a three inch cat5 cable going to a $15 tiny 
single port wifi router from a store down the street in Akihabara. The 
100baseT connection worked fine. Alas the tiny router couldn't _not_ 
NAT, and writing software to automatically navigate its built-in web 
page to associate with an access point was a rathole we didn't go down.

P.P.S. Oh, and we've connected boards over optical fiber using this 
transceiver chip. Those didn't call for mdio either, I'm not sure the 
VHDL changed at all, just board-level schematic changes. Technically 
that's 100baseF I believe.

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[Andrew Lunn]

> My vague recollection is this SOC only implemented full duplex 100baseT
> because they didn't have any hardware lying around that _couldn't_ talk to
> that.

It is pretty unusual to find hardware, now a days, which only does
10Mbp. So it is a somewhat theoretical use case. And as you say,
100Mbps is plenty fast for lots of applications.

What we need to think about is the path forwards, how MDIO and PHY
support can be added later, without breaking DT backwards
compatibility.

What you would normally do if there is no access to the PHY is use
fixed-link. It emulates a PHY, one that is always up and at a fixed
speed. See fixed-link in
Documentation/devicetree/bindings/net/ethernet-controller.yaml

That allows the MAC driver to use the phylib API. The MAC does not
hard coded the carrier up, phylib tells the MAC link is up, and phylib
manages the carrier.

What this means is, if sometime in the future MDIO is added, and
phylib gets access to the PHY, there are no MAC driver changes. Old DT
blobs, using fixed-link still work, and new DT blobs with MDIO, a PHY
node, and a phy-handle have working PHY.

If you don't do this now, adding support later will be messy, if you
don't want to break backwards compatibility with old DT blobs.

	Andrew

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Geert Uytterhoeven]

Hi Artur,

On Sat, 16 Aug 2025 at 14:06, Artur Rojek <contact@artur-rojek.eu> wrote:
> On 2025-08-16 10:19, Krzysztof Kozlowski wrote:
> > On 15/08/2025 21:48, Artur Rojek wrote:
> >> Add a documentation file to describe the Device Tree bindings for the
> >> Ethernet Media Access Controller found in the J-Core family of SoCs.
> >>
> >> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>

> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/net/jcore,emac.yaml

> >> +properties:
> >> +  compatible:
> >> +    const: jcore,emac
> >
> > You need SoC-based compatibles. And then also rename the file to match
> > it.
>
> Given how the top-most compatible of the bindings [1] of the board I am
> using has "jcore,j2-soc", this driver should probably go with
> "jcore,j2-emac".
>
> But as this is an FPGA design, I don't know how widespread the use is
> across other jcore derived SoCs (if any?).
> I will wait for Jeff (who's design this is) to clarify on that.
>
> PS. Too bad we already have other IP cores following the old pattern:
>
> > $ grep -r "compatible = \"jcore," bindings/ | grep -v "emac"
> > bindings/timer/jcore,pit.yaml:        compatible = "jcore,pit";
> > bindings/spi/jcore,spi.txt:   compatible = "jcore,spi2";
> > bindings/interrupt-controller/jcore,aic.yaml:        compatible =
> > "jcore,aic2";

I would go with "jcore,emac", as it is already in use.
If an incompatible version comes up, it should use a different
(versioned?) compatible value.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Krzysztof Kozlowski]

On 18/08/2025 08:43, Geert Uytterhoeven wrote:
>>>
>>> You need SoC-based compatibles. And then also rename the file to match
>>> it.
>>
>> Given how the top-most compatible of the bindings [1] of the board I am
>> using has "jcore,j2-soc", this driver should probably go with
>> "jcore,j2-emac".
>>
>> But as this is an FPGA design, I don't know how widespread the use is
>> across other jcore derived SoCs (if any?).
>> I will wait for Jeff (who's design this is) to clarify on that.
>>
>> PS. Too bad we already have other IP cores following the old pattern:
>>
>>> $ grep -r "compatible = \"jcore," bindings/ | grep -v "emac"
>>> bindings/timer/jcore,pit.yaml:        compatible = "jcore,pit";
>>> bindings/spi/jcore,spi.txt:   compatible = "jcore,spi2";
>>> bindings/interrupt-controller/jcore,aic.yaml:        compatible =
>>> "jcore,aic2";
> 
> I would go with "jcore,emac", as it is already in use.

git grep jcore,emac

Gives me zero?

> If an incompatible version comes up, it should use a different
> (versioned?) compatible value.

Versions are allowed if they follow some documented and known vendor SoC
versioning scheme. Is this the case here?

This is some sort of SoC, right? So it should have actual SoC name?



Best regards,
Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[D. Jeff Dionne]

On Aug 18, 2025, at 17:07, Krzysztof Kozlowski <krzk@kernel.org> wrote:

> git grep jcore,emac
> 
> Gives me zero?

Um, right.  It’s not upstream yet.  Thanks for your work to get that done, Artur.

>> If an incompatible version comes up, it should use a different
>> (versioned?) compatible value.
> 
> Versions are allowed if they follow some documented and known vendor SoC versioning scheme. Is this the case here?
> 
> This is some sort of SoC, right? So it should have actual SoC name?

No.  It’s a generic IP core for multiple SoCs, which do have names.

This is the correct naming scheme.  All compatible devices and SoCs match properly.
J.

> Best regards,
> Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Krzysztof Kozlowski]

On 18/08/2025 10:21, D. Jeff Dionne wrote:
> On Aug 18, 2025, at 17:07, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> 
>> git grep jcore,emac
>>
>> Gives me zero?
> 
> Um, right.  It’s not upstream yet.  Thanks for your work to get that done, Artur.
> 
>>> If an incompatible version comes up, it should use a different
>>> (versioned?) compatible value.
>>
>> Versions are allowed if they follow some documented and known vendor SoC versioning scheme. Is this the case here?
>>
>> This is some sort of SoC, right? So it should have actual SoC name?
> 
> No.  It’s a generic IP core for multiple SoCs, which do have names.

Then you need other SoCs compatibles, because we do not allow generic
items. See writing bindings.

> 
> This is the correct naming scheme.  All compatible devices and SoCs match properly.

No, it is not a correct naming scheme. Please read writing bindings.


Best regards,
Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Geert Uytterhoeven]

Hi Krzysztof,

On Mon, 18 Aug 2025 at 11:58, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> On 18/08/2025 10:21, D. Jeff Dionne wrote:
> > On Aug 18, 2025, at 17:07, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> >> git grep jcore,emac
> >>
> >> Gives me zero?
> >
> > Um, right.  It’s not upstream yet.  Thanks for your work to get that done, Artur.
> >
> >>> If an incompatible version comes up, it should use a different
> >>> (versioned?) compatible value.
> >>
> >> Versions are allowed if they follow some documented and known vendor SoC versioning scheme. Is this the case here?
> >>
> >> This is some sort of SoC, right? So it should have actual SoC name?
> >
> > No.  It’s a generic IP core for multiple SoCs, which do have names.
>
> Then you need other SoCs compatibles, because we do not allow generic
> items. See writing bindings.
>
> > This is the correct naming scheme.  All compatible devices and SoCs match properly.
>
> No, it is not a correct naming scheme. Please read writing bindings.

Can we please relax this for this specific compatible value?
All other devices in this specific hardware implementation were
accepted without SoC-specific compatible values ca. 9 years ago. AFAIK
the Ethernet MAC was the sole missing piece, because its Linux driver
was never attempted to be upstreamed before.

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Krzysztof Kozlowski]

On 18/08/2025 12:57, Geert Uytterhoeven wrote:
>>>
>>> No.  It’s a generic IP core for multiple SoCs, which do have names.
>>
>> Then you need other SoCs compatibles, because we do not allow generic
>> items. See writing bindings.
>>
>>> This is the correct naming scheme.  All compatible devices and SoCs match properly.
>>
>> No, it is not a correct naming scheme. Please read writing bindings.
> 
> Can we please relax this for this specific compatible value?

We can...

> All other devices in this specific hardware implementation were
> accepted without SoC-specific compatible values ca. 9 years ago. AFAIK
> the Ethernet MAC was the sole missing piece, because its Linux driver
> was never attempted to be upstreamed before.

...just provide some context and rationale in the commit msg.

Some (different) people pick up some irrelevant commits and use them as
argument in different discussions in style: it was allowed there, so I
can do the same.

Best regards,
Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[D. Jeff Dionne]

Something like:

J-Core SoCs are assembled with an SoC generator tool from standard components.  An SoC has a ROM from soc_gen with a Device Tree binary included.  Therefore, J-Core SoC devices are designed to ‘just work’ with linux, but this means the DT entires are generic, slightly different than standard device tree practice.

J

> On Aug 18, 2025, at 22:41, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> 
> On 18/08/2025 12:57, Geert Uytterhoeven wrote:
>>>> 
>>>> No.  It’s a generic IP core for multiple SoCs, which do have names.
>>> 
>>> Then you need other SoCs compatibles, because we do not allow generic
>>> items. See writing bindings.
>>> 
>>>> This is the correct naming scheme.  All compatible devices and SoCs match properly.
>>> 
>>> No, it is not a correct naming scheme. Please read writing bindings.
>> 
>> Can we please relax this for this specific compatible value?
> 
> We can...
> 
>> All other devices in this specific hardware implementation were
>> accepted without SoC-specific compatible values ca. 9 years ago. AFAIK
>> the Ethernet MAC was the sole missing piece, because its Linux driver
>> was never attempted to be upstreamed before.
> 
> ...just provide some context and rationale in the commit msg.
> 
> Some (different) people pick up some irrelevant commits and use them as
> argument in different discussions in style: it was allowed there, so I
> can do the same.
> 
> Best regards,
> Krzysztof

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Rob Landley]

On 8/18/25 03:07, Krzysztof Kozlowski wrote:
> On 18/08/2025 08:43, Geert Uytterhoeven wrote:
>>>>
>>>> You need SoC-based compatibles. And then also rename the file to match
>>>> it.
>>>
>>> Given how the top-most compatible of the bindings [1] of the board I am
>>> using has "jcore,j2-soc", this driver should probably go with
>>> "jcore,j2-emac".
>>>
>>> But as this is an FPGA design, I don't know how widespread the use is
>>> across other jcore derived SoCs (if any?).
>>> I will wait for Jeff (who's design this is) to clarify on that.
>>>
>>> PS. Too bad we already have other IP cores following the old pattern:
>>>
>>>> $ grep -r "compatible = \"jcore," bindings/ | grep -v "emac"
>>>> bindings/timer/jcore,pit.yaml:        compatible = "jcore,pit";
>>>> bindings/spi/jcore,spi.txt:   compatible = "jcore,spi2";
>>>> bindings/interrupt-controller/jcore,aic.yaml:        compatible =
>>>> "jcore,aic2";
>>
>> I would go with "jcore,emac", as it is already in use.
> 
> git grep jcore,emac
> 
> Gives me zero?

Ethernet support wasn't part of the original kernel submission, in part 
because we hadn't created the turtle board yet (and _still_ don't have a 
consumer retail arm to get them out into the world in less than triple 
digit lot sizes) and the off the shelf FPGA board we were pointing the 
open source community at circa 2016 (Numato Mimas V2) didn't include 
ethernet.

(Also, our internal driver had half an unfinished IEEE-1588 
implementation in it, which we kept meaning to clean out for public 
consumption. We took a different approach to time synchronization but 
had never produced a clean driver for external use until Artur decided 
to do one, which was very nice of him.)

>> If an incompatible version comes up, it should use a different
>> (versioned?) compatible value.
> 
> Versions are allowed if they follow some documented and known vendor SoC
> versioning scheme. Is this the case here?

This ethernet implementation hasn't significantly changed in 10 years.

Whenever we've needed something else we've done different I/O devices 
that weren't ethernet. (Even the USB 2.0 "ethernet" isn't technically 
ethernet, it made our board act as a USB dongle that showed up as an 
ethernet device to the computer it was plugged into so we could exchange 
data. No actual ethernetting really occurred, it's kind a like calling 
slip/ppp or virtio-net an ethernet interface.)

In theory gigabit phy would be a successor to this, A) no idea if they 
would share any code on the VHDL _or_ C side, B) that kind of phy 
requires 125mhz clock speed which is less cost effective in FPGA, 
especially now that AMD bought xilinx and doubled the prices. (We've 
stuck with LPDDR2 for similar reasons, although that's on the shorter 
term todo list to support. I mean yeah we _could_ use various FPGAs' 
builtin DDR3 library but we don't because we only want to use stuff we 
can implement ourselves in ASIC, and we need to not just test the state 
machine (minimum jedec clock speed 300mhz: kintex or vertex territory) 
but also commission the analog part of the circuit which is 
process-specific so you have to pick a fab to have them drawn for if 
you're avoiding NDAs and per-chip royalties for other people's black box 
libraries.

(Oh, and the higher up the FPGA stack you go the less likely yosys' open 
source FPGA tools are to work right, and the more NDA-clingy the closed 
source tools get, which is kind of annoying for a mostly non-US 
development team. (Lots of testing for $50 FPGAs, far less for $700 
FPGAs plus the more lawsuit-happy the vendors get about their crown 
jewels.) Gowin is trying but those suckers SUCK DOWN power, the ones 
I've seen are Lattice clones not Xilinx clones (ecp5 exists if we want 
_bigger_ lattice, the question is _faster_), and going that direction is 
really just a different kind of ecosystem lock-in...)

tl;dr: the 100baseT engine works fine for its niche, we've had no reason 
to fiddle with it.

> This is some sort of SoC, right? So it should have actual SoC name?

https://github.com/j-core/jcore-soc

Internally we have branches for various projects, which are named after 
the project not the base platform. It's "j2" because it's the dual 
processor version. J1 is what we use on ICE-40:

https://github.com/j-core/jcore-j1-ghdl

They're _mostly_ the same but the j2 SOC build has a whole automatic bus 
generator thing that pulls in dependencies (it's written in cloture and 
java) and the broken out j1 builds with just the 01 and 02 stages of the 
https://github.com/j-core/openlane-vhdl-build open source 
toolflow/toolchain. (There's a todo item to reorganize the repositories 
so j1 becomes a git submodule of j2 which would naturally keep them in 
sync, but it was all originally done in mercurial and needs a bit more 
massaging. Plus recently we've done a j1 fork removing the hardware 
multiplier and did a software multiplier toolchain, which hasn't made it 
over to the J2 side yet because it really needs a better configure 
mechanism (VHDL generics sure but what _selects_ them...) which REALLY 
says we need to rewrite the makefiles entirely... it's on the todo list.)

Rob

P.S. We haven't been pushing to github much since Microsoft bought it. 
I'm trying to convince Jeff to look at codeberg but he's hung up on the 
gitea->forgejo fork...

Re: [PATCH 3/3] net: j2: Introduce J-Core EMAC

[kernel test robot]

Hi Artur,

kernel test robot noticed the following build errors:

[auto build test ERROR on robh/for-next]
[also build test ERROR on linus/master v6.17-rc2 next-20250819]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Artur-Rojek/dt-bindings-vendor-prefixes-Document-J-Core/20250816-042354
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20250815194806.1202589-4-contact%40artur-rojek.eu
patch subject: [PATCH 3/3] net: j2: Introduce J-Core EMAC
config: m68k-randconfig-r113-20250819 (https://download.01.org/0day-ci/archive/20250820/202508200456.GIhKD5qv-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 8.5.0
reproduce: (https://download.01.org/0day-ci/archive/20250820/202508200456.GIhKD5qv-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508200456.GIhKD5qv-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/net/ethernet/jcore_emac.c: In function 'jcore_emac_set_rx_mode':
>> drivers/net/ethernet/jcore_emac.c:230:1: error: label at end of compound statement
    next_ha:
    ^~~~~~~


vim +230 drivers/net/ethernet/jcore_emac.c

   192	
   193	static void jcore_emac_set_rx_mode(struct net_device *ndev)
   194	{
   195		struct jcore_emac *priv = netdev_priv(ndev);
   196		struct netdev_hw_addr *ha;
   197		unsigned int reg, i, idx = 0, set_mask = 0, clear_mask = 0, addr = 0;
   198	
   199		if (ndev->flags & IFF_PROMISC)
   200			set_mask |= JCORE_EMAC_PROMISC;
   201		else
   202			clear_mask |= JCORE_EMAC_PROMISC;
   203	
   204		if (ndev->flags & IFF_ALLMULTI)
   205			set_mask |= JCORE_EMAC_MCAST;
   206		else
   207			clear_mask |= JCORE_EMAC_MCAST;
   208	
   209		regmap_update_bits(priv->map, JCORE_EMAC_CONTROL, set_mask | clear_mask,
   210				   set_mask);
   211	
   212		if (!(ndev->flags & IFF_MULTICAST))
   213			return;
   214	
   215		netdev_for_each_mc_addr(ha, ndev) {
   216			/* Only the first 3 octets are used in a hardware mcast mask. */
   217			memcpy(&addr, ha->addr, 3);
   218	
   219			for (i = 0; i < idx; i++) {
   220				regmap_read(priv->map, JCORE_EMAC_MCAST_MASK(i), &reg);
   221				if (reg == addr)
   222					goto next_ha;
   223			}
   224	
   225			regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(idx), addr);
   226			if (++idx >= JCORE_EMAC_MCAST_ADDRS) {
   227				netdev_warn(ndev, "Multicast list limit reached\n");
   228				break;
   229			}
 > 230	next_ha:
   231		}
   232	
   233		/* Clear the remaining mask entries. */
   234		for (i = idx; i < JCORE_EMAC_MCAST_ADDRS; i++)
   235			regmap_write(priv->map, JCORE_EMAC_MCAST_MASK(i), 0);
   236	}
   237	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Rob Herring]

On Mon, Aug 18, 2025 at 10:55:51PM +0900, D. Jeff Dionne wrote:
> Something like:

Please don't top post to maillists.

> J-Core SoCs are assembled with an SoC generator tool from standard 
> components.  An SoC has a ROM from soc_gen with a Device Tree binary 
> included.  Therefore, J-Core SoC devices are designed to ‘just work’ 
> with linux, but this means the DT entires are generic, slightly 
> different than standard device tree practice.

Yes. Though doesn't the SoC generator evolve/change? New features in the 
IP blocks, bug fixes, etc. Soft IP for FPGAs is similar I think. There 
we typically just require the versioning schema be documented and 
correlate to the IP versions (vs. made up v1, v2, v3).

This is all pretty niche I think, so I'm not too concerned about what 
you do here.

Rob

> 
> J
> 
> > On Aug 18, 2025, at 22:41, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > 
> > On 18/08/2025 12:57, Geert Uytterhoeven wrote:
> >>>> 
> >>>> No.  It’s a generic IP core for multiple SoCs, which do have names.
> >>> 
> >>> Then you need other SoCs compatibles, because we do not allow generic
> >>> items. See writing bindings.
> >>> 
> >>>> This is the correct naming scheme.  All compatible devices and SoCs match properly.
> >>> 
> >>> No, it is not a correct naming scheme. Please read writing bindings.
> >> 
> >> Can we please relax this for this specific compatible value?
> > 
> > We can...
> > 
> >> All other devices in this specific hardware implementation were
> >> accepted without SoC-specific compatible values ca. 9 years ago. AFAIK
> >> the Ethernet MAC was the sole missing piece, because its Linux driver
> >> was never attempted to be upstreamed before.
> > 
> > ...just provide some context and rationale in the commit msg.
> > 
> > Some (different) people pick up some irrelevant commits and use them as
> > argument in different discussions in style: it was allowed there, so I
> > can do the same.
> > 
> > Best regards,
> > Krzysztof
> 

Re: [PATCH 2/3] dt-bindings: net: Add support for J-Core EMAC

[Rob Landley]

On 8/20/25 16:39, Rob Herring wrote:
> On Mon, Aug 18, 2025 at 10:55:51PM +0900, D. Jeff Dionne wrote:
>> J-Core SoCs are assembled with an SoC generator tool from standard
>> components.  An SoC has a ROM from soc_gen with a Device Tree binary
>> included.  Therefore, J-Core SoC devices are designed to ‘just work’
>> with linux, but this means the DT entires are generic, slightly
>> different than standard device tree practice.
> 
> Yes. Though doesn't the SoC generator evolve/change? New features in the
> IP blocks, bug fixes, etc. Soft IP for FPGAs is similar I think.

The j-core guys almost never change the hardware interface on a deployed 
I/O device: when the existing interface is too limiting they do a new 
design with a different interface. (You'll notice in the github soc_top, 
components/ has ddr and ddr2, and components/misc has aic and aic2 from 
when the interrupt controller changed, for example. Those aren't version 
numbers, those are rewrites.)

Outputting a different constellation of devices/busses from the SOC 
generator is more akin to running "make menuconfig". There isn't an 
ancestor/descendant relationship there, it's a generator working from a 
configuration to instantiate and connect existing components.

> There
> we typically just require the versioning schema be documented and
> correlate to the IP versions (vs. made up v1, v2, v3).

There hasn't been a new version of the 100baseT specification recently.

The same chunk of bitstream is still driving the same PHY chips on the 
boards (or compatible, long out of patent) via the same small parallel 
bus at 50mhz. The engineers are no more interested in changing the 
kernel side interface than they are in changing the PHY side interface.

> This is all pretty niche I think, so I'm not too concerned about what 
> you do here.

Eh, not that niche. Just hardware development culture rather than 
software development culture. What's the model number on your microwave? 
If you need to replace it, how many versions will you advance?

Chip model numbers tend to be assigned by marketing well after the fact, 
and don't necessarily have a linear relationship even for the big boys 
making central components other people build entire systems around:

https://en.wikipedia.org/wiki/List_of_Qualcomm_Snapdragon_systems_on_chips

The Pentium II's development name was Kalmath, Pentium III was Katmai, 
then Pentium 4 was a space heater and everybody backed up and switched 
to "Pentium M" (which was MEANT to be a mobile chip but was instead a 
"not stupid" chip) and then they did "Core"... And then "Core 2" and 
"Core Duo" were different things and "Core 2 Duo" was both of those 
things, and then they had i3 and i5 and i7 but they all came out at the 
same time...

Jeep produced a "Cherokee" for 50 years and expected the user to step 
from a 1973 model to a 2023 model and be able to drive it the same 
(modulo major flag day changes like stick shift or leaded gasoline) with 
zero learning curve. Hardware developers of today go "here's an sd card, 
it goes click-click into your device and it just works, the only numbers 
you really need to know are price and capacity" (modulo microsd, but 
they still provide adapter sleds).

Software developers think that "DOS 2.0" and "DOS 3.0" or "Windows 3.0" 
and "Windows 3.1" being profoundly different and largely incompatible is 
just normal, and track that stuff minutely.

Different culture.

Rob