github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 17:47:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

net: ibm: emac: Clear MAL descriptors without memset

Browse Source 
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 <rosenp@gmail.com>
Link: https://patch.msgid.link/20260603230754.5535-1-rosenp@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Rosen Penev 2026-06-03 16:07:53 -07:00 committed by Jakub Kicinski
parent 8084fc9292
commit f0ba7f385d
1 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/net/ethernet/ibm/emac/core.c
View File

@ -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 *));