[PATCH 13/14] net: sh_eth: Workaround cache issues

[Ramon Fried]

On Wed, May 31, 2023 at 1:51 AM Marek Vasut
<marek.vasut+renesas at mailbox.org> wrote:
>
> From: Valentine Barshak <valentine.barshak at cogentembedded.com>
>
> U-Boot writes to RX packets when constructing replies.
> This can cause stale cached data to be written to RX
> buffer while we're receiving a packet. This causes RX
> packet corruption because we invalidate the cache right
> before processing the packet. Invalidate packet buffer
> cache when preparing RX descriptor as well. This seems
> to fix RX packet drops with high RX traffic.
>
> While at it flush the descriptors right before enabling
> RX/TX in sh_eth_tx_desc_init/sh_eth_rx_desc_init callbacks
> when they are ready instead of flushing after allocation.
>
> Signed-off-by: Valentine Barshak <valentine.barshak at cogentembedded.com>
> Reviewed-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
> ---
> Cc: Geert Uytterhoeven <geert+renesas at glider.be>
> Cc: Joe Hershberger <joe.hershberger at ni.com>
> Cc: Michal Simek <michal.simek at amd.com>
> Cc: Nishanth Menon <nm at ti.com>
> Cc: Ramon Fried <rfried.dev at gmail.com>
> ---
>  drivers/net/sh_eth.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/sh_eth.c b/drivers/net/sh_eth.c
> index 95042daade0..7314caadfdc 100644
> --- a/drivers/net/sh_eth.c
> +++ b/drivers/net/sh_eth.c
> @@ -142,6 +142,8 @@ static void sh_eth_recv_finish(struct sh_eth_dev *eth)
>  {
>         struct sh_eth_info *port_info = &eth->port_info[eth->port];
>
> +       invalidate_cache(ADDR_TO_P2(port_info->rx_desc_cur->rd2), MAX_BUF_SIZE);
> +
>         /* Make current descriptor available again */
>         if (port_info->rx_desc_cur->rd0 & RD_RDLE)
>                 port_info->rx_desc_cur->rd0 = RD_RACT | RD_RDLE;
> @@ -210,8 +212,6 @@ static int sh_eth_tx_desc_init(struct sh_eth_dev *eth)
>                 goto err;
>         }
>
> -       flush_cache_wback(port_info->tx_desc_alloc, alloc_desc_size);
> -
>         /* Make sure we use a P2 address (non-cacheable) */
>         port_info->tx_desc_base =
>                 (struct tx_desc_s *)ADDR_TO_P2((uintptr_t)port_info->tx_desc_alloc);
> @@ -229,6 +229,7 @@ static int sh_eth_tx_desc_init(struct sh_eth_dev *eth)
>         cur_tx_desc--;
>         cur_tx_desc->td0 |= TD_TDLE;
>
> +       flush_cache_wback(port_info->tx_desc_alloc, alloc_desc_size);
>         /*
>          * Point the controller to the tx descriptor list. Must use physical
>          * addresses
> @@ -264,8 +265,6 @@ static int sh_eth_rx_desc_init(struct sh_eth_dev *eth)
>                 goto err;
>         }
>
> -       flush_cache_wback(port_info->rx_desc_alloc, alloc_desc_size);
> -
>         /* Make sure we use a P2 address (non-cacheable) */
>         port_info->rx_desc_base =
>                 (struct rx_desc_s *)ADDR_TO_P2((uintptr_t)port_info->rx_desc_alloc);
> @@ -299,6 +298,9 @@ static int sh_eth_rx_desc_init(struct sh_eth_dev *eth)
>         cur_rx_desc--;
>         cur_rx_desc->rd0 |= RD_RDLE;
>
> +       invalidate_cache(port_info->rx_buf_alloc, NUM_RX_DESC * MAX_BUF_SIZE);
> +       flush_cache_wback(port_info->rx_desc_alloc, alloc_desc_size);
> +
>         /* Point the controller to the rx descriptor list */
>         sh_eth_write(port_info, ADDR_TO_PHY(port_info->rx_desc_base), RDLAR);
>  #if defined(SH_ETH_TYPE_GETHER) || defined(SH_ETH_TYPE_RZ)
> --
> 2.39.2
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>