net: ethernet: oa_tc6: implement mac-phy interrupt

The MAC-PHY interrupt is asserted when the following conditions are met.

Receive chunks available - This interrupt is asserted when the previous
data footer had no receive data chunks available and once the receive
data chunks become available for reading. On reception of the first data
header this interrupt will be deasserted.

Transmit chunk credits available - This interrupt is asserted when the
previous data footer indicated no transmit credits available and once the
transmit credits become available for transmitting transmit data chunks.
On reception of the first data header this interrupt will be deasserted.

Extended status event - This interrupt is asserted when the previous data
footer indicated no extended status and once the extended event become
available. In this case the host should read status #0 register to know
the corresponding error/event. On reception of the first data header this
interrupt will be deasserted.

Reviewed-by: Andrew Lunn <[e-mail]>
Signed-off-by: Parthiban Veerasooran <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/oa_tc6.c

···
 	u16 tx_credits;
 	u8 rx_chunks_available;
 	bool rx_buf_overflow;
+	bool int_flag;
 };
 
 enum oa_tc6_header_type {
···
 
 		spi_len = oa_tc6_prepare_spi_tx_buf_for_rx_chunks(tc6, spi_len);
 
+		if (tc6->int_flag) {
+			tc6->int_flag = false;
+			if (spi_len == 0) {
+				oa_tc6_add_empty_chunks_to_spi_buf(tc6, 1);
+				spi_len = OA_TC6_CHUNK_SIZE;
+			}
+		}
+
 		if (spi_len == 0)
 			break;
 
···
 	int ret;
 
 	while (likely(!kthread_should_stop())) {
-		/* This kthread will be waken up if there is a tx skb */
+		/* 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->waiting_tx_skb ||
+					 tc6->int_flag ||
 					 kthread_should_stop());
 
 		if (kthread_should_stop())
···
 					     value);
 
 	return 0;
+}
+
+static irqreturn_t oa_tc6_macphy_isr(int irq, void *data)
+{
+	struct oa_tc6 *tc6 = data;
+
+	/* MAC-PHY interrupt can occur for the following reasons.
+	 * - availability of tx credits if it was 0 before and not reported in
+	 *   the previous rx footer.
+	 * - availability of rx chunks if it was 0 before and not reported in
+	 *   the previous rx footer.
+	 * - 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;
 }
 
 /**
···
 
 	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);
+	if (ret) {
+		dev_err(&tc6->spi->dev, "Failed to request macphy isr %d\n",
+			ret);
+		goto kthread_stop;
+	}
+
+	/* oa_tc6_sw_reset_macphy() function resets and clears the MAC-PHY reset
+	 * complete status. IRQ is also asserted on reset completion and it is
+	 * remain asserted until MAC-PHY receives a data chunk. So performing an
+	 * empty data chunk transmission will deassert the IRQ. Refer section
+	 * 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);
+
 	return tc6;
 
+kthread_stop:
+	kthread_stop(tc6->spi_thread);
 phy_exit:
 	oa_tc6_phy_exit(tc6);
 	return NULL;