Subject: [PATCH] net: ethernet: mtk_eth_soc: add support for coherent DMA
From: Felix Fietkau <[email-masked]>
Date: Fri, 4 Sep 2020 18:36:06 +0200

It improves performance by eliminating the need for a cache flush on rx and tx

Signed-off-by: Felix Fietkau <[email-masked]>
---

--- a/arch/arm64/boot/dts/mediatek/mt7622.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt7622.dtsi
@@ -357,7 +357,7 @@
 		};
 
 		cci_control2: slave-if@5000 {
-			compatible = "arm,cci-400-ctrl-if";
+			compatible = "arm,cci-400-ctrl-if", "syscon";
 			interface-type = "ace";
 			reg = <0x5000 0x1000>;
 		};
@@ -969,6 +969,8 @@
 		power-domains = <&scpsys MT7622_POWER_DOMAIN_ETHSYS>;
 		mediatek,ethsys = <&ethsys>;
 		mediatek,sgmiisys = <&sgmiisys>;
+		mediatek,cci-control = <&cci_control2>;
+		dma-coherent;
 		#address-cells = <1>;
 		#size-cells = <0>;
 		status = "disabled";
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -9,6 +9,7 @@
 #include <linux/of_device.h>
 #include <linux/of_mdio.h>
 #include <linux/of_net.h>
+#include <linux/of_address.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
 #include <linux/clk.h>
@@ -2485,6 +2486,13 @@ static int mtk_hw_init(struct mtk_eth *e
 	if (ret)
 		goto err_disable_pm;
 
+	if (of_dma_is_coherent(eth->dev->of_node)) {
+		u32 mask = ETHSYS_DMA_AG_MAP_PDMA | ETHSYS_DMA_AG_MAP_QDMA |
+			   ETHSYS_DMA_AG_MAP_PPE;
+
+		regmap_update_bits(eth->ethsys, ETHSYS_DMA_AG_MAP, mask, mask);
+	}
+
 	if (MTK_HAS_CAPS(eth->soc->caps, MTK_SOC_MT7628)) {
 		ret = device_reset(eth->dev);
 		if (ret) {
@@ -3083,6 +3091,16 @@ static int mtk_probe(struct platform_dev
 		}
 	}
 
+	if (of_dma_is_coherent(pdev->dev.of_node)) {
+		struct regmap *cci;
+
+		cci = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+						      "mediatek,cci-control");
+		/* enable CPU/bus coherency */
+		if (!IS_ERR(cci))
+			regmap_write(cci, 0, 3);
+	}
+
 	if (MTK_HAS_CAPS(eth->soc->caps, MTK_SGMII)) {
 		eth->sgmii = devm_kzalloc(eth->dev, sizeof(*eth->sgmii),
 					  GFP_KERNEL);
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
@@ -435,6 +435,12 @@
 #define RSTCTRL_FE		BIT(6)
 #define RSTCTRL_PPE		BIT(31)
 
+/* ethernet dma channel agent map */
+#define ETHSYS_DMA_AG_MAP	0x408
+#define ETHSYS_DMA_AG_MAP_PDMA	BIT(0)
+#define ETHSYS_DMA_AG_MAP_QDMA	BIT(1)
+#define ETHSYS_DMA_AG_MAP_PPE	BIT(2)
+
 /* SGMII subsystem config registers */
 /* Register to auto-negotiation restart */
 #define SGMSYS_PCS_CONTROL_1	0x0