linux-kernel - [PATCH RFC v2 3/5] net: stmmac: dwmac-meson8b: use picoseconds for the RGMII RX delay

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Date:   Sun, 15 Nov 2020 19:52:08 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     davem@...emloft.net, kuba@...nel.org,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, netdev@...r.kernel.org
Cc:     jianxin.pan@...ogic.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, khilman@...libre.com,
        narmstrong@...libre.com, jbrunet@...libre.com, andrew@...n.ch,
        f.fainelli@...il.com,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH RFC v2 3/5] net: stmmac: dwmac-meson8b: use picoseconds for the RGMII RX delay

Amlogic Meson G12A, G12B and SM1 SoCs have a more advanced RGMII RX
delay register which allows picoseconds precision. Parse the new
"amlogic,rgmii-rx-delay-ps" property or fall back to the old
"amlogic,rx-delay-ns".

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
 .../ethernet/stmicro/stmmac/dwmac-meson8b.c   | 22 ++++++++++++-------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
index e27e2e7a53fd..03fce678b9f5 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
@@ -83,7 +83,7 @@ struct meson8b_dwmac {
 	phy_interface_t			phy_mode;
 	struct clk			*rgmii_tx_clk;
 	u32				tx_delay_ns;
-	u32				rx_delay_ns;
+	u32				rx_delay_ps;
 	struct clk			*timing_adj_clk;
 };
 
@@ -276,7 +276,7 @@ static int meson8b_init_prg_eth(struct meson8b_dwmac *dwmac)
 	tx_dly_config = FIELD_PREP(PRG_ETH0_TXDLY_MASK,
 				   dwmac->tx_delay_ns >> 1);
 
-	if (dwmac->rx_delay_ns == 2)
+	if (dwmac->rx_delay_ps == 2000)
 		rx_dly_config = PRG_ETH0_ADJ_ENABLE | PRG_ETH0_ADJ_SETUP;
 	else
 		rx_dly_config = 0;
@@ -406,14 +406,20 @@ static int meson8b_dwmac_probe(struct platform_device *pdev)
 				 &dwmac->tx_delay_ns))
 		dwmac->tx_delay_ns = 2;
 
-	/* use 0ns as fallback since this is what most boards actually use */
-	if (of_property_read_u32(pdev->dev.of_node, "amlogic,rx-delay-ns",
-				 &dwmac->rx_delay_ns))
-		dwmac->rx_delay_ns = 0;
+	/* RX delay defaults to 0ps since this is what many boards use */
+	if (of_property_read_u32(pdev->dev.of_node,
+				 "amlogic,rgmii-rx-delay-ps",
+				  &dwmac->rx_delay_ps)) {
+		if (!of_property_read_u32(pdev->dev.of_node,
+					  "amlogic,rx-delay-ns",
+					  &dwmac->rx_delay_ps))
+			/* convert ns to ps */
+			dwmac->rx_delay_ps *= 1000;
+	}
 
-	if (dwmac->rx_delay_ns != 0 && dwmac->rx_delay_ns != 2) {
+	if (dwmac->rx_delay_ps != 0 && dwmac->rx_delay_ps != 2000) {
 		dev_err(&pdev->dev,
-			"The only allowed RX delays values are: 0ns, 2ns");
+			"The only allowed RX delays values are: 0ps, 2000ps");
 		ret = -EINVAL;
 		goto err_remove_config_dt;
 	}
-- 
2.29.2