[PATCH net-next 1/2] net: stmmac: use circ_buf helpers for descriptors
From: Russell King (Oracle) <hidden>
Date: 2026-02-23 11:42:00
Also in:
linux-arm-kernel
Subsystem:
networking drivers, stmmac ethernet driver, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Maxime Chevallier, Linus Torvalds
The stmmac descriptor queues are circular buffers, operated as far as the hardware is concerned as either a ring, or a chain that loops back on itself. From the software perspective, it forms a circular buffer. We have a few places which calculate the number of in-use and free entries in these circular buffers, for which we have macros for. Use CIRC_CNT() and CIRC_SPACE() as appropriate to calculate these values. Validating, for stmmac_tx_avail(), which uses CIRC_SPACE(): dirty_tx = 1, cur_tx = 0 -> 0 dirty_tx = 0, cur_tx = 0 -> dma_tx_size - 1 dirty_tx = 0, cur_tx = 1 -> dma_tx_size - 2 dirty_tx passed as end, reduced by one. cur_tx passed as start. Output on sane computers is identical. For stmmac_rx_dirty(), which uses CIRC_CNT(): dirty_rx = 1, cur_rx = 0 -> dma_rx_size - 1 dirty_rx = 0, cur_rx = 0 -> 0 dirty_rx = 0, cur_rx = 1 -> 1 dirty_rx passed as start, cur_rx passed as end. Output is identical. Same validation performed on the is_last_segment calculation, which also gets converted to CIRC_CNT(). Signed-off-by: Russell King (Oracle) <redacted> --- .../net/ethernet/stmicro/stmmac/stmmac_main.c | 23 ++++++------------- 1 file changed, 7 insertions(+), 16 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a2a0985e8c37..3277aecc5454 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c@@ -14,6 +14,7 @@ https://bugzilla.stlinux.com/ *******************************************************************************/ +#include <linux/circ_buf.h> #include <linux/clk.h> #include <linux/kernel.h> #include <linux/interrupt.h>
@@ -355,14 +356,9 @@ static void print_pkt(unsigned char *buf, int len) static inline u32 stmmac_tx_avail(struct stmmac_priv *priv, u32 queue) { struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue]; - u32 avail; - if (tx_q->dirty_tx > tx_q->cur_tx) - avail = tx_q->dirty_tx - tx_q->cur_tx - 1; - else - avail = priv->dma_conf.dma_tx_size - tx_q->cur_tx + tx_q->dirty_tx - 1; - - return avail; + return CIRC_SPACE(tx_q->cur_tx, tx_q->dirty_tx, + priv->dma_conf.dma_tx_size); } /**
@@ -373,14 +369,9 @@ static inline u32 stmmac_tx_avail(struct stmmac_priv *priv, u32 queue) static inline u32 stmmac_rx_dirty(struct stmmac_priv *priv, u32 queue) { struct stmmac_rx_queue *rx_q = &priv->dma_conf.rx_queue[queue]; - u32 dirty; - - if (rx_q->dirty_rx <= rx_q->cur_rx) - dirty = rx_q->cur_rx - rx_q->dirty_rx; - else - dirty = priv->dma_conf.dma_rx_size - rx_q->dirty_rx + rx_q->cur_rx; - return dirty; + return CIRC_CNT(rx_q->cur_rx, rx_q->dirty_rx, + priv->dma_conf.dma_rx_size); } static bool stmmac_eee_tx_busy(struct stmmac_priv *priv)
@@ -4571,8 +4562,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev) /* If we only have one entry used, then the first entry is the last * segment. */ - is_last_segment = ((tx_q->cur_tx - first_entry) & - (priv->dma_conf.dma_tx_size - 1)) == 1; + is_last_segment = CIRC_CNT(tx_q->cur_tx, first_entry,, + priv->dma_conf.dma_tx_size) == 1; /* Complete the first descriptor before granting the DMA */ stmmac_prepare_tso_tx_desc(priv, first, 1, proto_hdr_len, 0, 1,
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2.47.3