From: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
Date: Sun, 6 Nov 2022 22:11:52 +0100
> The function lan966x_fdma_rx_get_frame was unmapping the frame from
> device and check also if the frame was received on a valid port. And
> only after that it tried to generate the skb.
> Move this check in a different function, in preparation for xdp
> support. Such that xdp to be added here and the
> lan966x_fdma_rx_get_frame to be used only when giving the skb to upper
> layers.
>
> Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
> ---
> .../ethernet/microchip/lan966x/lan966x_fdma.c | 85 +++++++++++++------
> .../ethernet/microchip/lan966x/lan966x_main.h | 9 ++
> 2 files changed, 69 insertions(+), 25 deletions(-)
[...]
> -static struct sk_buff *lan966x_fdma_rx_get_frame(struct lan966x_rx *rx)
> +static int lan966x_fdma_rx_check_frame(struct lan966x_rx *rx, u64 *src_port)
> {
> struct lan966x *lan966x = rx->lan966x;
> - u64 src_port, timestamp;
> struct lan966x_db *db;
> - struct sk_buff *skb;
> struct page *page;
>
> - /* Get the received frame and unmap it */
> db = &rx->dcbs[rx->dcb_index].db[rx->db_index];
> page = rx->page[rx->dcb_index][rx->db_index];
> + if (unlikely(!page))
> + return FDMA_ERROR;
>
> dma_sync_single_for_cpu(lan966x->dev, (dma_addr_t)db->dataptr,
> FDMA_DCB_STATUS_BLOCKL(db->status),
> DMA_FROM_DEVICE);
>
> + dma_unmap_single_attrs(lan966x->dev, (dma_addr_t)db->dataptr,
> + PAGE_SIZE << rx->page_order, DMA_FROM_DEVICE,
> + DMA_ATTR_SKIP_CPU_SYNC);
> +
> + lan966x_ifh_get_src_port(page_address(page), src_port);
> + if (WARN_ON(*src_port >= lan966x->num_phys_ports))
> + return FDMA_ERROR;
> +
> + return FDMA_PASS;
How about making this function return s64, which would be "src_port
or negative error", and dropping the second argument @src_port (the
example of calling it below)?
> +}
> +
> +static struct sk_buff *lan966x_fdma_rx_get_frame(struct lan966x_rx *rx,
> + u64 src_port)
> +{
[...]
> - skb = lan966x_fdma_rx_get_frame(rx);
> + counter++;
>
> - rx->page[rx->dcb_index][rx->db_index] = NULL;
> - rx->dcb_index++;
> - rx->dcb_index &= FDMA_DCB_MAX - 1;
> + switch (lan966x_fdma_rx_check_frame(rx, &src_port)) {
> + case FDMA_PASS:
> + break;
> + case FDMA_ERROR:
> + lan966x_fdma_rx_free_page(rx);
> + lan966x_fdma_rx_advance_dcb(rx);
> + goto allocate_new;
> + }
So, here you could do (if you want to keep the current flow)::
src_port = lan966x_fdma_rx_check_frame(rx);
switch (src_port) {
case 0 .. S64_MAX: // for example
break;
case FDMA_ERROR: // must be < 0
lan_966x_fdma_rx_free_page(rx);
...
}
But given that the error path is very unlikely and cold, I would
prefer if-else over switch case:
src_port = lan966x_fdma_rx_check_frame(rx);
if (unlikely(src_port < 0)) {
lan_966x_fdma_rx_free_page(rx);
...
goto allocate_new;
}
>
> + skb = lan966x_fdma_rx_get_frame(rx, src_port);
> + lan966x_fdma_rx_advance_dcb(rx);
> if (!skb)
> - break;
> + goto allocate_new;
>
> napi_gro_receive(&lan966x->napi, skb);
> - counter++;
> }
>
> +allocate_new:
> /* Allocate new pages and map them */
> while (dcb_reload != rx->dcb_index) {
> db = &rx->dcbs[dcb_reload].db[rx->db_index];
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> index 4ec33999e4df6..464fb5e4a8ff6 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> @@ -100,6 +100,15 @@ enum macaccess_entry_type {
> ENTRYTYPE_MACV6,
> };
>
> +/* FDMA return action codes for checking if the frame is valid
> + * FDMA_PASS, frame is valid and can be used
> + * FDMA_ERROR, something went wrong, stop getting more frames
> + */
> +enum lan966x_fdma_action {
> + FDMA_PASS = 0,
> + FDMA_ERROR,
> +};
> +
> struct lan966x_port;
>
> struct lan966x_db {
> --
> 2.38.0
Thanks,
Olek
