On Mon, Feb 27, 2017 at 12:09:02PM +0200, Mikko Perttunen wrote:

On 23.02.2017 19:24, Thierry Reding wrote:

quoted

From: Thierry Reding <redacted>

Program the receive queue size based on the RX FIFO size and enable
hardware flow control for large FIFOs.

Signed-off-by: Thierry Reding <redacted>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4.h     | 12 +++++++
 drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c | 43 ++++++++++++++++++++++--
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index db45134fddf0..9acc1f1252b3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h

@@ -180,6 +180,7 @@ enum power_event {
 #define MTL_OP_MODE_TSF			BIT(1)

 #define MTL_OP_MODE_TQS_MASK		GENMASK(24, 16)
+#define MTL_OP_MODE_TQS_SHIFT		16

 #define MTL_OP_MODE_TTC_MASK		0x70
 #define MTL_OP_MODE_TTC_SHIFT		4

@@ -193,6 +194,17 @@ enum power_event {
 #define MTL_OP_MODE_TTC_384		(6 << MTL_OP_MODE_TTC_SHIFT)
 #define MTL_OP_MODE_TTC_512		(7 << MTL_OP_MODE_TTC_SHIFT)

+#define MTL_OP_MODE_RQS_MASK		GENMASK(29, 20)
+#define MTL_OP_MODE_RQS_SHIFT		20
+
+#define MTL_OP_MODE_RFD_MASK		GENMASK(19, 14)
+#define MTL_OP_MODE_RFD_SHIFT		14
+
+#define MTL_OP_MODE_RFA_MASK		GENMASK(13, 8)
+#define MTL_OP_MODE_RFA_SHIFT		8
+
+#define MTL_OP_MODE_EHFC		BIT(7)
+
 #define MTL_OP_MODE_RTC_MASK		0x18
 #define MTL_OP_MODE_RTC_SHIFT		3

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
index 8d249f3b34c8..03d230201960 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c

@@ -185,8 +185,9 @@ static void dwmac4_rx_watchdog(void __iomem *ioaddr, u32 riwt)
 }

 static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
-				    int rxmode, u32 channel)
+				    int rxmode, u32 channel, int rxfifosz)
 {
+	unsigned int rqs = rxfifosz / 256 - 1;
 	u32 mtl_tx_op, mtl_rx_op, mtl_rx_int;

 	/* Following code only done for channel 0, other channels not yet

@@ -252,6 +253,44 @@ static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
 			mtl_rx_op |= MTL_OP_MODE_RTC_128;
 	}

+	mtl_rx_op &= ~MTL_OP_MODE_RQS_MASK;
+	mtl_rx_op |= rqs << MTL_OP_MODE_RQS_SHIFT;
+
+	/* enable flow control only if each channel gets 4 KiB or more FIFO */
+	if (rxfifosz >= 4096) {
+		unsigned int rfd, rfa;
+
+		mtl_rx_op |= MTL_OP_MODE_EHFC;
+
+		switch (rxfifosz) {
+		case 4096:
+			rfd = 0x03;
+			rfa = 0x01;
+			break;
+
+		case 8192:
+			rfd = 0x06;
+			rfa = 0x0a;
+			break;
+
+		case 16384:
+			rfd = 0x06;
+			rfa = 0x12;
+			break;
+
+		default:
+			rfd = 0x06;
+			rfa = 0x1e;
+			break;
+		}

Are these values correct? In the 4096 case, rfd > rfa, in all other cases
the other way around. In any case it would be useful to have a comment
clarifying the thresholds in bytes.

I'll investigate. To be honest I simply took this from Stephen's U-Boot
driver since that's already tested. I trust Stephen, so I didn't bother
double-checking.

Thierry