[PATCH net-next v6 06/14] net: lan966x: use a dedicated device for DMA operations
Daniel Machon
daniel.machon at microchip.com
Wed Sep 9 06:00:08 PDT 2026
In preparation for the PCIe FDMA implementation, add lan966x->dma_dev,
resolved once at probe time, and use it for every DMA operation the
FDMA path performs: coherent allocations, streaming mappings and the RX
page pool. Natively, dma_dev is lan966x->dev, so there is no functional
change.
Since dma_dev differs from dev only on the PCIe path, add
lan966x_is_pci() on top of it, for the later PCIe patches to key off.
Signed-off-by: Daniel Machon <daniel.machon at microchip.com>
---
.../net/ethernet/microchip/lan966x/lan966x_fdma.c | 30 +++++++++++-----------
.../net/ethernet/microchip/lan966x/lan966x_main.c | 16 ++++++++++++
.../net/ethernet/microchip/lan966x/lan966x_main.h | 10 ++++++++
3 files changed, 41 insertions(+), 15 deletions(-)
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
index 1311b79bd11f..15fc59cb4ad7 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
@@ -80,7 +80,7 @@ static int lan966x_fdma_rx_alloc_page_pool(struct lan966x_rx *rx)
.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
.pool_size = rx->fdma.n_dcbs,
.nid = NUMA_NO_NODE,
- .dev = lan966x->dev,
+ .dev = lan966x->dma_dev,
.dma_dir = DMA_FROM_DEVICE,
.offset = XDP_PACKET_HEADROOM,
.max_len = rx->max_mtu -
@@ -126,7 +126,7 @@ static int lan966x_fdma_rx_alloc(struct lan966x_rx *rx)
if (err)
return err;
- err = fdma_alloc_coherent(lan966x->dev, fdma);
+ err = fdma_alloc_coherent(lan966x->dma_dev, fdma);
if (err) {
page_pool_destroy(rx->page_pool);
return err;
@@ -210,7 +210,7 @@ static int lan966x_fdma_tx_alloc(struct lan966x_tx *tx)
if (!tx->dcbs_buf)
return -ENOMEM;
- err = fdma_alloc_coherent(lan966x->dev, fdma);
+ err = fdma_alloc_coherent(lan966x->dma_dev, fdma);
if (err)
goto out;
@@ -230,7 +230,7 @@ static void lan966x_fdma_tx_free(struct lan966x_tx *tx)
struct lan966x *lan966x = tx->lan966x;
kfree(tx->dcbs_buf);
- fdma_free_coherent(lan966x->dev, &tx->fdma);
+ fdma_free_coherent(lan966x->dma_dev, &tx->fdma);
}
static void lan966x_fdma_tx_activate(struct lan966x_tx *tx)
@@ -355,7 +355,7 @@ static void lan966x_fdma_tx_clear_buf(struct lan966x *lan966x, int weight)
dcb_buf->used = false;
if (dcb_buf->use_skb) {
- dma_unmap_single(lan966x->dev,
+ dma_unmap_single(lan966x->dma_dev,
dcb_buf->dma_addr,
dcb_buf->len,
DMA_TO_DEVICE);
@@ -364,7 +364,7 @@ static void lan966x_fdma_tx_clear_buf(struct lan966x *lan966x, int weight)
napi_consume_skb(dcb_buf->data.skb, weight);
} else {
if (dcb_buf->xdp_ndo)
- dma_unmap_single(lan966x->dev,
+ dma_unmap_single(lan966x->dma_dev,
dcb_buf->dma_addr,
dcb_buf->len,
DMA_TO_DEVICE);
@@ -400,7 +400,7 @@ static int lan966x_fdma_rx_check_frame(struct lan966x_rx *rx, u64 *src_port)
if (unlikely(!page))
return FDMA_ERROR;
- dma_sync_single_for_cpu(lan966x->dev,
+ dma_sync_single_for_cpu(lan966x->dma_dev,
(dma_addr_t)db->dataptr + XDP_PACKET_HEADROOM,
FDMA_DCB_STATUS_BLOCKL(db->status),
DMA_FROM_DEVICE);
@@ -635,11 +635,11 @@ int lan966x_fdma_xmit_xdpf(struct lan966x_port *port, void *ptr, u32 len)
lan966x_ifh_set_bypass(ifh, 1);
lan966x_ifh_set_port(ifh, BIT_ULL(port->chip_port));
- dma_addr = dma_map_single(lan966x->dev,
+ dma_addr = dma_map_single(lan966x->dma_dev,
xdpf->data - IFH_LEN_BYTES,
xdpf->len + IFH_LEN_BYTES,
DMA_TO_DEVICE);
- if (dma_mapping_error(lan966x->dev, dma_addr)) {
+ if (dma_mapping_error(lan966x->dma_dev, dma_addr)) {
ret = NETDEV_TX_OK;
goto out;
}
@@ -655,7 +655,7 @@ int lan966x_fdma_xmit_xdpf(struct lan966x_port *port, void *ptr, u32 len)
lan966x_ifh_set_port(ifh, BIT_ULL(port->chip_port));
dma_addr = page_pool_get_dma_addr(page);
- dma_sync_single_for_device(lan966x->dev,
+ dma_sync_single_for_device(lan966x->dma_dev,
dma_addr + XDP_PACKET_HEADROOM,
len + IFH_LEN_BYTES,
DMA_TO_DEVICE);
@@ -734,9 +734,9 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
memcpy(skb->data, ifh, IFH_LEN_BYTES);
skb_put(skb, 4);
- dma_addr = dma_map_single(lan966x->dev, skb->data, skb->len,
+ dma_addr = dma_map_single(lan966x->dma_dev, skb->data, skb->len,
DMA_TO_DEVICE);
- if (dma_mapping_error(lan966x->dev, dma_addr)) {
+ if (dma_mapping_error(lan966x->dma_dev, dma_addr)) {
dev->stats.tx_dropped++;
err = NETDEV_TX_OK;
goto release;
@@ -842,7 +842,7 @@ static int lan966x_fdma_reload(struct lan966x *lan966x, int new_mtu)
page_pool_put_full_page(page_pool,
old_pages[i][j], false);
- fdma_free_coherent(lan966x->dev, &fdma_rx_old);
+ fdma_free_coherent(lan966x->dma_dev, &fdma_rx_old);
page_pool_destroy(page_pool);
@@ -992,7 +992,7 @@ int lan966x_fdma_init(struct lan966x *lan966x)
err = lan966x_fdma_tx_alloc(&lan966x->tx);
if (err) {
- fdma_free_coherent(lan966x->dev, &lan966x->rx.fdma);
+ fdma_free_coherent(lan966x->dma_dev, &lan966x->rx.fdma);
page_pool_destroy(lan966x->rx.page_pool);
return err;
}
@@ -1014,7 +1014,7 @@ void lan966x_fdma_deinit(struct lan966x *lan966x)
napi_disable(&lan966x->napi);
lan966x_fdma_rx_free_pages(&lan966x->rx);
- fdma_free_coherent(lan966x->dev, &lan966x->rx.fdma);
+ fdma_free_coherent(lan966x->dma_dev, &lan966x->rx.fdma);
page_pool_destroy(lan966x->rx.page_pool);
lan966x_fdma_tx_free(&lan966x->tx);
}
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 1179a6e127c5..2741f7c9fa4c 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -7,6 +7,7 @@
#include <linux/ip.h>
#include <linux/of.h>
#include <linux/of_net.h>
+#include <linux/pci.h>
#include <linux/phy/phy.h>
#include <linux/platform_device.h>
#include <linux/reset.h>
@@ -1081,6 +1082,20 @@ static int lan966x_reset_switch(struct lan966x *lan966x)
return 0;
}
+/* When enumerated over PCIe, dev is a platform device with no
+ * iommus/dma-ranges of its own, so DMA must target the PCIe endpoint instead.
+ * The result differs from dev only in that case; lan966x_is_pci() relies on it.
+ */
+static struct device *lan966x_get_dma_dev(struct device *dev)
+{
+ for (struct device *p = dev->parent; p; p = p->parent) {
+ if (dev_is_pci(p))
+ return p;
+ }
+
+ return dev;
+}
+
static int lan966x_probe(struct platform_device *pdev)
{
struct fwnode_handle *ports, *portnp;
@@ -1094,6 +1109,7 @@ static int lan966x_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, lan966x);
lan966x->dev = &pdev->dev;
+ lan966x->dma_dev = lan966x_get_dma_dev(lan966x->dev);
if (!device_get_mac_address(&pdev->dev, mac_addr)) {
ether_addr_copy(lan966x->base_mac, mac_addr);
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
index 83c361abb789..3f09f8ddf620 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
@@ -270,6 +270,9 @@ struct lan966x_skb_cb {
struct lan966x {
struct device *dev;
+ /* Device used for DMA; the PCIe endpoint when enumerated over PCIe. */
+ struct device *dma_dev;
+
u8 num_phys_ports;
struct lan966x_port **ports;
@@ -573,6 +576,13 @@ void lan966x_fdma_wakeup_netdev(struct lan966x *lan966x);
int lan966x_fdma_get_max_frame(struct lan966x *lan966x);
int lan966x_qsys_sw_status(struct lan966x *lan966x);
+/* dma_dev differs from dev only on the PCIe path. */
+static inline bool lan966x_is_pci(struct lan966x *lan966x)
+{
+ return IS_ENABLED(CONFIG_MCHP_LAN966X_PCI) &&
+ lan966x->dma_dev != lan966x->dev;
+}
+
int lan966x_lag_port_join(struct lan966x_port *port,
struct net_device *brport_dev,
struct net_device *bond,
--
2.34.1
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