From f0ba7f385de12d237f31c9439256647b25294a01 Mon Sep 17 00:00:00 2001 From: Rosen Penev Date: Wed, 3 Jun 2026 16:07:53 -0700 Subject: [PATCH] net: ibm: emac: Clear MAL descriptors without memset Clear MAL descriptor rings with explicit field stores instead of memset(). The descriptor rings are carved from MAL coherent DMA memory, which may be mapped uncached on 32-bit powerpc. The optimized memset() path can use dcbz there and trigger an alignment warning. Use WRITE_ONCE() for each field to prevent the compiler from merging the stores back into a memset() call. The skb tracking arrays remain ordinary CPU memory and still use memset(). Signed-off-by: Rosen Penev Link: https://patch.msgid.link/20260603230754.5535-1-rosenp@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/ibm/emac/core.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index d2194b406c9e..b7568d96aa47 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -1162,6 +1162,17 @@ static void emac_clean_rx_ring(struct emac_instance *dev) } } +static void emac_clear_mal_desc(struct mal_descriptor *desc, int count) +{ + int i; + + for (i = 0; i < count; i++) { + WRITE_ONCE(desc[i].ctrl, 0); + WRITE_ONCE(desc[i].data_len, 0); + WRITE_ONCE(desc[i].data_ptr, 0); + } +} + static int __emac_prepare_rx_skb(struct sk_buff *skb, struct emac_instance *dev, int slot) { @@ -3089,8 +3100,8 @@ static int emac_probe(struct platform_device *ofdev) DBG(dev, "rx_desc %p" NL, dev->rx_desc); /* Clean rings */ - memset(dev->tx_desc, 0, NUM_TX_BUFF * sizeof(struct mal_descriptor)); - memset(dev->rx_desc, 0, NUM_RX_BUFF * sizeof(struct mal_descriptor)); + emac_clear_mal_desc(dev->tx_desc, NUM_TX_BUFF); + emac_clear_mal_desc(dev->rx_desc, NUM_RX_BUFF); memset(dev->tx_skb, 0, NUM_TX_BUFF * sizeof(struct sk_buff *)); memset(dev->rx_skb, 0, NUM_RX_BUFF * sizeof(struct sk_buff *));