[net-next v4 3/3] net: ethernet: mtk_eth_soc: change code to skip first IRQ completely

[Frank Wunderlich <linux@fw-web.de>]

From: Frank Wunderlich <frank-w@public-files.de>

On SoCs without MTK_SHARED_INT capability (mt7621 + mt7628) the first
IRQ (eth->irq[0]) was read but never used. Do not read it and reduce
the IRQ-count to 2 because of skipped index 0.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
---
v4:
- drop >2 condition as max is already 2 and drop the else continue
- update comment to explain which IRQs are taken in legacy way
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 20 ++++++++++++++++----
 drivers/net/ethernet/mediatek/mtk_eth_soc.h |  4 ++--
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 3ecb399dcf81..f3fcbb00822c 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -3341,16 +3341,28 @@ static int mtk_get_irqs(struct platform_device *pdev, struct mtk_eth *eth)
 {
 	int i;
 
+	/* future SoCs beginning with MT7988 should use named IRQs in dts */
 	eth->irq[MTK_ETH_IRQ_TX] = platform_get_irq_byname(pdev, "tx");
 	eth->irq[MTK_ETH_IRQ_RX] = platform_get_irq_byname(pdev, "rx");
 	if (eth->irq[MTK_ETH_IRQ_TX] >= 0 && eth->irq[MTK_ETH_IRQ_RX] >= 0)
 		return 0;
 
+	/* legacy way:
+	 * On MTK_SHARED_INT SoCs (MT7621 + MT7628) the first IRQ is taken from
+	 * devicetree and used for rx+tx.
+	 * On SoCs with non-shared IRQ the first was not used, second entry is
+	 * TX and third is RX.
+	 */
+
 	for (i = 0; i < MTK_ETH_IRQ_MAX; i++) {
-		if (MTK_HAS_CAPS(eth->soc->caps, MTK_SHARED_INT) && i > 0)
-			eth->irq[i] = eth->irq[MTK_ETH_IRQ_SHARED];
-		else
-			eth->irq[i] = platform_get_irq(pdev, i);
+		if (MTK_HAS_CAPS(eth->soc->caps, MTK_SHARED_INT)) {
+			if (i == 0)
+				eth->irq[MTK_ETH_IRQ_SHARED] = platform_get_irq(pdev, i);
+			else
+				eth->irq[i] = eth->irq[MTK_ETH_IRQ_SHARED];
+		} else {
+			eth->irq[i] = platform_get_irq(pdev, i + 1);
+		}
 
 		if (eth->irq[i] < 0) {
 			dev_err(&pdev->dev, "no IRQ%d resource found\n", i);
diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.h b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
index 96b724dca0e2..9d91fe721ad0 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
@@ -643,8 +643,8 @@
 #define MTK_MAC_FSM(x)		(0x1010C + ((x) * 0x100))
 
 #define MTK_ETH_IRQ_SHARED	0
-#define MTK_ETH_IRQ_TX		1
-#define MTK_ETH_IRQ_RX		2
+#define MTK_ETH_IRQ_TX		0
+#define MTK_ETH_IRQ_RX		1
 #define MTK_ETH_IRQ_MAX		(MTK_ETH_IRQ_RX + 1)
 
 struct mtk_rx_dma {
-- 
2.43.0