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Subject[RFC v1 2/2] net: stmmac: dwmac-meson8b: add support for the RX delay configuration
Date
DO NOT MERGE THIS!

Test results:
- Akaso M8S (not upstream yet) Meson8m2 with RMII PHY: no change
- Odroid-C1 Meson8b with RTL8211F RGMII PHY:
phy-mode = "rgmii" still works
phy-mode = "rgmii-id" works now
- Khadas VIM2 GXM with RTL8211F RGMII PHY:
phy-mode = "rgmii" is now broken!
phy-mode = "rgmii-id" works

The public A311D datasheet [0] mentions these bits in the PRG_ETH0 (also
call PRG_ETH0_REG) register:
- bit[13]: RMII & RGMII mode, Enable data delay adjustment and
calibration logic.
- bit[14]: Set RXDV and RXD setup time, data is aligned with index 0.
When set to 1, auto delay and skew.
- bit[19:15]: Set bit14 to 0. RMII & RGMII mode. Capture input data at
clock index equal to adj_delay.
- bit[24:20]: RMII & RGMII mode. 5 Bits correspondent to
{RXDV, RXD[3:0]}, set to 1 will delay the data capture by 1 cycle.
(do all of these bits have the same meaning for all supported SoCs:
Meson8b, Meson8m2, GXBB, GXL, GXM, AXG, G12A, G12B, SM1?)

The public "Amlogic Ethernet controller user guide" recommends the
following settings.
RMII: adj_enable = 1, adj_setup = 0, adj_delay = 18, adj_skew = 0x0
RGMII: adj_enable = 1, adj_setup = 1, adj_delay = 4, adj_skew = 0xc
(shouldn't adj_delay be 0 for the RGMII mode based on the register
description above?)

Do we need to expose adj_delay and adj_skew to devicetree?
How do I know which value to set for each board?

[0] https://dl.khadas.com/Hardware/VIM3/Datasheet/A311D_Datasheet_01_Wesion.pdf
[1] http://openlinux.amlogic.com/@api/deki/files/75/=Amlogic_Ethenet_controller_user_Guide.pdf

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
.../ethernet/stmicro/stmmac/dwmac-meson8b.c | 59 ++++++++++---------
1 file changed, 32 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
index 1483761ab1e6..af25eb1aea41 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
@@ -33,6 +33,10 @@
#define PRG_ETH0_CLK_M250_SEL_SHIFT 4
#define PRG_ETH0_CLK_M250_SEL_MASK GENMASK(4, 4)

+/* TX clock delay in ns = "8ns / 4 * tx_dly_val" (where 8ns are exactly one
+ * cycle of the 125MHz RGMII TX clock):
+ * 0ns = 0x0, 2ns = 0x1, 4ns = 0x2, 6ns = 0x3
+ */
#define PRG_ETH0_TXDLY_MASK GENMASK(6, 5)

/* divider for the result of m250_sel */
@@ -44,6 +48,11 @@
#define PRG_ETH0_INVERTED_RMII_CLK BIT(11)
#define PRG_ETH0_TX_AND_PHY_REF_CLK BIT(12)

+#define PRG_ETH0_ADJ_ENABLE BIT(13)
+#define PRG_ETH0_ADJ_SETUP BIT(14)
+#define PRG_ETH0_ADJ_DELAY GENMASK(19, 15)
+#define PRG_ETH0_ADJ_SKEW GENMASK(24, 20)
+
#define MUX_CLK_NUM_PARENTS 2

struct meson8b_dwmac;
@@ -241,29 +250,38 @@ static int meson_axg_set_phy_mode(struct meson8b_dwmac *dwmac)

static int meson8b_init_prg_eth(struct meson8b_dwmac *dwmac)
{
+ u8 tx_dly_val = dwmac->tx_delay_ns >> 1;
+ u32 delay_config;
int ret;
- u8 tx_dly_val = 0;

switch (dwmac->phy_mode) {
case PHY_INTERFACE_MODE_RGMII:
+ delay_config = FIELD_PREP(PRG_ETH0_TXDLY_MASK, tx_dly_val);
+ delay_config |= PRG_ETH0_ADJ_ENABLE | PRG_ETH0_ADJ_SETUP;
+ break;
case PHY_INTERFACE_MODE_RGMII_RXID:
- /* TX clock delay in ns = "8ns / 4 * tx_dly_val" (where
- * 8ns are exactly one cycle of the 125MHz RGMII TX clock):
- * 0ns = 0x0, 2ns = 0x1, 4ns = 0x2, 6ns = 0x3
- */
- tx_dly_val = dwmac->tx_delay_ns >> 1;
- /* fall through */
-
- case PHY_INTERFACE_MODE_RGMII_ID:
+ delay_config = FIELD_PREP(PRG_ETH0_TXDLY_MASK, tx_dly_val);
+ break;
case PHY_INTERFACE_MODE_RGMII_TXID:
+ delay_config = PRG_ETH0_ADJ_ENABLE | PRG_ETH0_ADJ_SETUP;
+ break;
+ case PHY_INTERFACE_MODE_RGMII_ID:
+ case PHY_INTERFACE_MODE_RMII:
+ default:
+ delay_config = 0;
+ break;
+ };
+
+ meson8b_dwmac_mask_bits(dwmac, PRG_ETH0, PRG_ETH0_TXDLY_MASK |
+ PRG_ETH0_ADJ_ENABLE | PRG_ETH0_ADJ_SETUP |
+ PRG_ETH0_ADJ_DELAY | PRG_ETH0_ADJ_SKEW,
+ delay_config);
+
+ if (phy_interface_mode_is_rgmii(dwmac->phy_mode)) {
/* only relevant for RMII mode -> disable in RGMII mode */
meson8b_dwmac_mask_bits(dwmac, PRG_ETH0,
PRG_ETH0_INVERTED_RMII_CLK, 0);

- meson8b_dwmac_mask_bits(dwmac, PRG_ETH0, PRG_ETH0_TXDLY_MASK,
- FIELD_PREP(PRG_ETH0_TXDLY_MASK,
- tx_dly_val));
-
/* Configure the 125MHz RGMII TX clock, the IP block changes
* the output automatically (= without us having to configure
* a register) based on the line-speed (125MHz for Gbit speeds,
@@ -286,24 +304,11 @@ static int meson8b_init_prg_eth(struct meson8b_dwmac *dwmac)
devm_add_action_or_reset(dwmac->dev,
(void(*)(void *))clk_disable_unprepare,
dwmac->rgmii_tx_clk);
- break;
-
- case PHY_INTERFACE_MODE_RMII:
+ } else {
/* invert internal clk_rmii_i to generate 25/2.5 tx_rx_clk */
meson8b_dwmac_mask_bits(dwmac, PRG_ETH0,
PRG_ETH0_INVERTED_RMII_CLK,
PRG_ETH0_INVERTED_RMII_CLK);
-
- /* TX clock delay cannot be configured in RMII mode */
- meson8b_dwmac_mask_bits(dwmac, PRG_ETH0, PRG_ETH0_TXDLY_MASK,
- 0);
-
- break;
-
- default:
- dev_err(dwmac->dev, "unsupported phy-mode %s\n",
- phy_modes(dwmac->phy_mode));
- return -EINVAL;
}

/* enable TX_CLK and PHY_REF_CLK generator */
--
2.24.1
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