Hi Julian, On Wed, Apr 14, 2021 at 8:53 AM Julian Wiedmann <j...@linux.ibm.com> wrote: > > On a cursory glance, using __netdev_alloc_skb_ip_align() here should > allow you to get rid of all the RX_HEAD_PADDING gymnastics. > > And also avoid the need for setting RX_CFG_B_RX_PAD_2_, as the > NET_IP_ALIGN part would no longer get dma-mapped.
That's an excellent suggestion, and I'll definitely keep that in mind for the future. In this case, I'm not sure if it could work. This NIC has multi-buffer frames. The dma-ed skbs represent frame fragments. A flag in the descriptor ring indicates if an skb is "first". If first, we can reserve the padding. Otherwise, we cannot. because that would corrupt a fragment in the middle. At the time of skb allocation, we do not know whether that skb will be "first". https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/microchip/lan743x_main.c?h=v5.12-rc7#n2125 Maybe I'm missing a trick here? Feel free to suggest improvements, it's always much appreciated. Sven
