net: stmmac: Add HW descriptor prefetch setting for DWMAC Core 5.20 onwards

DWMAC Core 5.20 onwards supports HW descriptor prefetching.
Additionally, it also depends on platform specific RTL configuration.
This capability could be enabled by setting DMA_Mode bit-19 (DCHE).

So, to enable this cability, platform must set plat->dma_cfg->dche = true
and the DWMAC core version must be 5.20 onwards. Else, this capability
wouldn`t be configured
Signed-off-by: Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/common.h

@@ -33,6 +33,7 @@
 #define DWMAC_CORE_4_10		0x41
 #define DWMAC_CORE_5_00		0x50
 #define DWMAC_CORE_5_10		0x51
+#define DWMAC_CORE_5_20		0x52
 #define DWXGMAC_CORE_2_10	0x21
 #define DWXLGMAC_CORE_2_00	0x20
 

drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c

@@ -162,12 +162,18 @@ static void dwmac4_dma_init(void __iomem *ioaddr,
 
 	writel(value, ioaddr + DMA_SYS_BUS_MODE);
 
+	value = readl(ioaddr + DMA_BUS_MODE);
+
 	if (dma_cfg->multi_msi_en) {
-		value = readl(ioaddr + DMA_BUS_MODE);
 		value &= ~DMA_BUS_MODE_INTM_MASK;
 		value |= (DMA_BUS_MODE_INTM_MODE1 << DMA_BUS_MODE_INTM_SHIFT);
-		writel(value, ioaddr + DMA_BUS_MODE);
 	}
+
+	if (dma_cfg->dche)
+		value |= DMA_BUS_MODE_DCHE;
+
+	writel(value, ioaddr + DMA_BUS_MODE);
+
 }
 
 static void _dwmac4_dump_dma_regs(void __iomem *ioaddr, u32 channel,

drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h

@@ -25,6 +25,7 @@
 #define DMA_TBS_CTRL			0x00001050
 
 /* DMA Bus Mode bitmap */
+#define DMA_BUS_MODE_DCHE		BIT(19)
 #define DMA_BUS_MODE_INTM_MASK		GENMASK(17, 16)
 #define DMA_BUS_MODE_INTM_SHIFT		16
 #define DMA_BUS_MODE_INTM_MODE1		0x1

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -6849,6 +6849,11 @@ int stmmac_dvr_probe(struct device *device,
 	if (ret)
 		goto error_hw_init;
 
+	/* Only DWMAC core version 5.20 onwards supports HW descriptor prefetch.
+	 */
+	if (priv->synopsys_id < DWMAC_CORE_5_20)
+		priv->plat->dma_cfg->dche = false;
+
 	stmmac_check_ether_addr(priv);
 
 	ndev->netdev_ops = &stmmac_netdev_ops;

include/linux/stmmac.h

@@ -97,6 +97,7 @@ struct stmmac_dma_cfg {
 	bool aal;
 	bool eame;
 	bool multi_msi_en;
+	bool dche;
 };
 
 #define AXI_BLEN	7