[PATCH net v4 0/4] MAC-PHY interrupt changed to level triggered interrupt

[PATCH net v4 0/4] MAC-PHY interrupt changed to level triggered interrupt

[Selvamani Rajagopal via B4 Relay]

According to OPEN Alliance 10BASE-T1x MAC-PHY Serial Interface
specification, MAC-PHY interrupt is "active low, level triggered".
The specification mentions about the conditions in which the IRQ
is asserted and deasserted.

Bug is inadvertently introduced by treating the IRQ in the OA TC6
framework driver and in dt-binding YAML file as edge triggered.

Changes are done in two files
 - OA TC6 framework Ethernet driver
 - YAML file for the vendor that already uses OA TC6 framework.

Maintainer for this driver is already informed and aware of these
changes. Testing for these changes was done in onsemi's setup and
found to be working.

To: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
To: Andrew Lunn <andrew+netdev@lunn.ch>
To: David S. Miller <davem@davemloft.net>
To: Eric Dumazet <edumazet@google.com>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
Cc: Piergiorgio Beruto <pier.beruto@onsemi.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Conor Dooley <conor.dooley@microchip.com>
Cc: devicetree@vger.kernel.org
Cc: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

Changes in v4:

- IRQ handler is changed to interrupt handler + wake up thread
  to interrupt handler + threaded irq. Threaded irq mechanism
  is better suited for level triggered interrupt. Because it can
  keep the interrupt disabled until interrupting conditions are 
  handled by a handler thread.
- SPI data handling function is called again on EAGAIN error code
  as it indicates RX buffer overflow error, which requires draining
  the bad data chunks.
 
  - Changed wakeup thread to threaded IRQ 
  - RX buffer overflow is handled before threaded irq returns

- Link to v3: https://lore.kernel.org/r/20260601-level-trigger-v3-0-da73e7010532@onsemi.com

---
Selvamani Rajagopal (4):
      net: ethernet: oa_tc6: Interrupt is active low, level triggered.
      net: ethernet: oa_tc6: No return on rx buffer overflow error
      net: ethernet: oa_tc6: mdiobus->parent initialized with NULL
      dt-bindings: net: updated interrupt type to be active low, level triggered

 .../devicetree/bindings/net/microchip,lan8650.yaml |  2 +-
 drivers/net/ethernet/oa_tc6.c                      | 66 +++++++---------------
 2 files changed, 21 insertions(+), 47 deletions(-)
---
base-commit: 0aa05daef7848a5ac11158949dc73cd741995dc1
change-id: 20260531-level-trigger-8cb1a83af034

Best regards,
-- 
Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

[PATCH net v4 1/4] net: ethernet: oa_tc6: Interrupt is active low, level triggered.

[Selvamani Rajagopal via B4 Relay]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

According OPEN Alliance 10BASET1x MAC-PHY Serial Interface
specification, interrupt is active low, level triggered.

Fixes: 2c6ce5354453 ("net: ethernet: oa_tc6: implement mac-phy interrupt")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

Changes in v4:
  Interrupt handling mechanism changed to threaded irq because it is
  best suited to handle level triggered interrupt. Threaded irq
  automatically blocks further interrupts until interrupting
  conditions are cleared by its handler.

Changes in v3:
 interrupt registered as level triggerred
---
 drivers/net/ethernet/oa_tc6.c | 61 ++++++++++++-------------------------------
 1 file changed, 17 insertions(+), 44 deletions(-)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index 91a906a7918a..e2c0843207f2 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -7,6 +7,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/iopoll.h>
+#include <linux/interrupt.h>
 #include <linux/mdio.h>
 #include <linux/phy.h>
 #include <linux/oa_tc6.h>
@@ -121,8 +122,6 @@ struct oa_tc6 {
 	struct sk_buff *ongoing_tx_skb;
 	struct sk_buff *waiting_tx_skb;
 	struct sk_buff *rx_skb;
-	struct task_struct *spi_thread;
-	wait_queue_head_t spi_wq;
 	u16 tx_skb_offset;
 	u16 spi_data_tx_buf_offset;
 	u16 tx_credits;
@@ -1105,29 +1104,18 @@ static int oa_tc6_try_spi_transfer(struct oa_tc6 *tc6)
 	return 0;
 }
 
-static int oa_tc6_spi_thread_handler(void *data)
+static irqreturn_t oa_tc6_macphy_threaded_irq(int irq, void *data)
 {
 	struct oa_tc6 *tc6 = data;
-	int ret;
-
-	while (likely(!kthread_should_stop())) {
-		/* This kthread will be waken up if there is a tx skb or mac-phy
-		 * interrupt to perform spi transfer with tx chunks.
-		 */
-		wait_event_interruptible(tc6->spi_wq, tc6->int_flag ||
-					 (tc6->waiting_tx_skb &&
-					 tc6->tx_credits) ||
-					 kthread_should_stop());
-
-		if (kthread_should_stop())
-			break;
+	int ret = 0;
 
+	while (tc6->int_flag || (tc6->waiting_tx_skb && tc6->tx_credits)) {
 		ret = oa_tc6_try_spi_transfer(tc6);
 		if (ret)
-			return ret;
+			break;
 	}
 
-	return 0;
+	return IRQ_HANDLED;
 }
 
 static int oa_tc6_update_buffer_status_from_register(struct oa_tc6 *tc6)
@@ -1162,10 +1150,8 @@ static irqreturn_t oa_tc6_macphy_isr(int irq, void *data)
 	 * - extended status event not reported in the previous rx footer.
 	 */
 	tc6->int_flag = true;
-	/* Wake spi kthread to perform spi transfer */
-	wake_up_interruptible(&tc6->spi_wq);
-
-	return IRQ_HANDLED;
+	/* Wake IRQ thread to perform spi transfer */
+	return IRQ_WAKE_THREAD;
 }
 
 /**
@@ -1217,8 +1203,8 @@ netdev_tx_t oa_tc6_start_xmit(struct oa_tc6 *tc6, struct sk_buff *skb)
 	tc6->waiting_tx_skb = skb;
 	spin_unlock_bh(&tc6->tx_skb_lock);
 
-	/* Wake spi kthread to perform spi transfer */
-	wake_up_interruptible(&tc6->spi_wq);
+	/* Wake the threaded IRQ to perform spi transfer. */
+	irq_wake_thread(tc6->spi->irq, tc6);
 
 	return NETDEV_TX_OK;
 }
@@ -1311,24 +1297,15 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, struct net_device *netdev)
 		goto phy_exit;
 	}
 
-	init_waitqueue_head(&tc6->spi_wq);
-
-	tc6->spi_thread = kthread_run(oa_tc6_spi_thread_handler, tc6,
-				      "oa-tc6-spi-thread");
-	if (IS_ERR(tc6->spi_thread)) {
-		dev_err(&tc6->spi->dev, "Failed to create SPI thread\n");
-		goto phy_exit;
-	}
-
-	sched_set_fifo(tc6->spi_thread);
-
-	ret = devm_request_irq(&tc6->spi->dev, tc6->spi->irq, oa_tc6_macphy_isr,
-			       IRQF_TRIGGER_FALLING, dev_name(&tc6->spi->dev),
-			       tc6);
+	ret = devm_request_threaded_irq(&tc6->spi->dev, tc6->spi->irq,
+					oa_tc6_macphy_isr,
+					oa_tc6_macphy_threaded_irq,
+					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+					dev_name(&tc6->spi->dev), tc6);
 	if (ret) {
 		dev_err(&tc6->spi->dev, "Failed to request macphy isr %d\n",
 			ret);
-		goto kthread_stop;
+		goto phy_exit;
 	}
 
 	/* oa_tc6_sw_reset_macphy() function resets and clears the MAC-PHY reset
@@ -1338,12 +1315,9 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, struct net_device *netdev)
 	 * 7.7 and 9.2.8.8 in the OPEN Alliance specification for more details.
 	 */
 	tc6->int_flag = true;
-	wake_up_interruptible(&tc6->spi_wq);
+	irq_wake_thread(tc6->spi->irq, tc6);
 
 	return tc6;
-
-kthread_stop:
-	kthread_stop(tc6->spi_thread);
 phy_exit:
 	oa_tc6_phy_exit(tc6);
 	return NULL;
@@ -1357,7 +1331,6 @@ EXPORT_SYMBOL_GPL(oa_tc6_init);
 void oa_tc6_exit(struct oa_tc6 *tc6)
 {
 	oa_tc6_phy_exit(tc6);
-	kthread_stop(tc6->spi_thread);
 	dev_kfree_skb_any(tc6->ongoing_tx_skb);
 	dev_kfree_skb_any(tc6->waiting_tx_skb);
 	dev_kfree_skb_any(tc6->rx_skb);

-- 
2.43.0

[PATCH net v4 2/4] net: ethernet: oa_tc6: No return on rx buffer overflow error

[Selvamani Rajagopal via B4 Relay]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

On RX buffer overflow error, the bad data chunks must
be thrown away and code should look for a data chunk with
"start valid" bit set, which would indicate next valid MAC
frame. In this change, oa_tc6_try_spi_transfer is called
again if it returns error code EAGAIN. This helps to
recover from the error gracefully.

Fixes: 2c6ce5354453 ("net: ethernet: oa_tc6: implement mac-phy interrupt")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

Changes in v4:
   new patch
---
 drivers/net/ethernet/oa_tc6.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index e2c0843207f2..20c9e98d1d60 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -1111,6 +1111,8 @@ static irqreturn_t oa_tc6_macphy_threaded_irq(int irq, void *data)
 
 	while (tc6->int_flag || (tc6->waiting_tx_skb && tc6->tx_credits)) {
 		ret = oa_tc6_try_spi_transfer(tc6);
+		if (ret == -EAGAIN)
+			continue;
 		if (ret)
 			break;
 	}

-- 
2.43.0

[PATCH net v4 3/4] net: ethernet: oa_tc6: mdiobus->parent initialized with NULL

[Selvamani Rajagopal via B4 Relay]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

As "dev" pointer in oa_tc6 structure is never initialized,
mbiosub->parent was initialized with NULL.  This change
fixes the issue.

Fixes: 2c6ce5354453 ("net: ethernet: oa_tc6: implement mac-phy interrupt")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

Changes in v4:
   new patch
---
 drivers/net/ethernet/oa_tc6.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index 20c9e98d1d60..0710a5a8dcde 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -108,7 +108,6 @@
 
 /* Internal structure for MAC-PHY drivers */
 struct oa_tc6 {
-	struct device *dev;
 	struct net_device *netdev;
 	struct phy_device *phydev;
 	struct mii_bus *mdiobus;
@@ -517,7 +516,7 @@ static int oa_tc6_mdiobus_register(struct oa_tc6 *tc6)
 	tc6->mdiobus->read_c45 = oa_tc6_mdiobus_read_c45;
 	tc6->mdiobus->write_c45 = oa_tc6_mdiobus_write_c45;
 	tc6->mdiobus->name = "oa-tc6-mdiobus";
-	tc6->mdiobus->parent = tc6->dev;
+	tc6->mdiobus->parent = &tc6->spi->dev;
 
 	snprintf(tc6->mdiobus->id, ARRAY_SIZE(tc6->mdiobus->id), "%s",
 		 dev_name(&tc6->spi->dev));

-- 
2.43.0

[PATCH net v4 4/4] dt-bindings: net: updated interrupt type to be active low, level triggered

[Selvamani Rajagopal via B4 Relay]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

According to OPEN Alliance 10BASE-T1x MACPHY Serial Interface (TC6)
specification, interrupt type is active low, level triggered interrupt.

Fixes: ac49b950bea9 ("dt-bindings: net: add Microchip's LAN865X 10BASE-T1S MACPHY")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

changes in v4:
  no change
changes in v3
  interrupts entry changed to level triggered from edge triggered
---
 Documentation/devicetree/bindings/net/microchip,lan8650.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/microchip,lan8650.yaml b/Documentation/devicetree/bindings/net/microchip,lan8650.yaml
index 61e11d4a07c4..766ff58147ae 100644
--- a/Documentation/devicetree/bindings/net/microchip,lan8650.yaml
+++ b/Documentation/devicetree/bindings/net/microchip,lan8650.yaml
@@ -67,7 +67,7 @@ examples:
         pinctrl-names = "default";
         pinctrl-0 = <&eth0_pins>;
         interrupt-parent = <&gpio>;
-        interrupts = <6 IRQ_TYPE_EDGE_FALLING>;
+        interrupts = <6 IRQ_TYPE_LEVEL_LOW>;
         local-mac-address = [04 05 06 01 02 03];
         spi-max-frequency = <15000000>;
       };

-- 
2.43.0