[PATCH net-next v5 04/13] net: lan966x: add FDMA LLP register write helper
From: Daniel Machon <daniel.machon@microchip.com>
Date: 2026-05-20 08:14:10
Also in:
bpf, linux-arm-kernel, lkml
Subsystem:
microchip lan966x ethernet driver, networking drivers, the rest · Maintainers:
Horatiu Vultur, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
The FDMA Link List Pointer (LLP) register points to the first DCB in the chain and must be written before the channel is activated. This tells the FDMA engine where to begin DMA transfers. Move the LLP register writes from the channel start/activate functions into the allocation functions and introduce a shared lan966x_fdma_llp_configure() helper. This is needed because the upcoming PCIe FDMA path writes ATU-translated addresses to the LLP registers instead of DMA addresses. Keeping the writes in the shared start/activate path would overwrite these translated addresses. Tested-by: Herve Codina <herve.codina@bootlin.com> Signed-off-by: Daniel Machon <daniel.machon@microchip.com> --- .../net/ethernet/microchip/lan966x/lan966x_fdma.c | 29 ++++++++++------------ 1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
index f8ce735a7fc0..6c5761e886d4 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c@@ -109,6 +109,13 @@ static int lan966x_fdma_rx_alloc_page_pool(struct lan966x_rx *rx) return PTR_ERR_OR_ZERO(rx->page_pool); } +static void lan966x_fdma_llp_configure(struct lan966x *lan966x, u64 addr, + u8 channel_id) +{ + lan_wr(lower_32_bits(addr), lan966x, FDMA_DCB_LLP(channel_id)); + lan_wr(upper_32_bits(addr), lan966x, FDMA_DCB_LLP1(channel_id)); +} + static int lan966x_fdma_rx_alloc(struct lan966x_rx *rx) { struct lan966x *lan966x = rx->lan966x;
@@ -127,6 +134,9 @@ static int lan966x_fdma_rx_alloc(struct lan966x_rx *rx) fdma_dcbs_init(fdma, FDMA_DCB_INFO_DATAL(fdma->db_size), FDMA_DCB_STATUS_INTR); + lan966x_fdma_llp_configure(lan966x, (u64)fdma->dma, + fdma->channel_id); + return 0; }
@@ -136,14 +146,6 @@ static void lan966x_fdma_rx_start(struct lan966x_rx *rx) struct fdma *fdma = &rx->fdma; u32 mask; - /* When activating a channel, first is required to write the first DCB - * address and then to activate it - */ - lan_wr(lower_32_bits((u64)fdma->dma), lan966x, - FDMA_DCB_LLP(fdma->channel_id)); - lan_wr(upper_32_bits((u64)fdma->dma), lan966x, - FDMA_DCB_LLP1(fdma->channel_id)); - lan_wr(FDMA_CH_CFG_CH_DCB_DB_CNT_SET(fdma->n_dbs) | FDMA_CH_CFG_CH_INTR_DB_EOF_ONLY_SET(1) | FDMA_CH_CFG_CH_INJ_PORT_SET(0) |
@@ -214,6 +216,9 @@ static int lan966x_fdma_tx_alloc(struct lan966x_tx *tx) fdma_dcbs_init(fdma, 0, 0); + lan966x_fdma_llp_configure(lan966x, (u64)fdma->dma, + fdma->channel_id); + return 0; out:
@@ -235,14 +240,6 @@ static void lan966x_fdma_tx_activate(struct lan966x_tx *tx) struct fdma *fdma = &tx->fdma; u32 mask; - /* When activating a channel, first is required to write the first DCB - * address and then to activate it - */ - lan_wr(lower_32_bits((u64)fdma->dma), lan966x, - FDMA_DCB_LLP(fdma->channel_id)); - lan_wr(upper_32_bits((u64)fdma->dma), lan966x, - FDMA_DCB_LLP1(fdma->channel_id)); - lan_wr(FDMA_CH_CFG_CH_DCB_DB_CNT_SET(fdma->n_dbs) | FDMA_CH_CFG_CH_INTR_DB_EOF_ONLY_SET(1) | FDMA_CH_CFG_CH_INJ_PORT_SET(0) |
--
2.34.1