[5/6] net: dwc_eth_qos: Invalidate RX packet DMA buffer

This patch prevents an issue where the RX packet might have been
accessed by the CPU, which now has cached data from the packet in
the caches and possibly various write buffers, and these data may
be evicted from the caches into the DRAM while the buffer is also
written by the DMA.

By invalidating the buffer after the CPU accessed it and before the
DMA populates the buffer, it is assured that the buffer will not be
corrupted.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Joe Hershberger <joe.hershberger at ni.com>
Cc: Patrice Chotard <patrice.chotard at st.com>
Cc: Patrick Delaunay <patrick.delaunay at st.com>
Cc: Ramon Fried <rfried.dev at gmail.com>
Cc: Stephen Warren <swarren at nvidia.com>
---
 drivers/net/dwc_eth_qos.c | 6 ++++++
 1 file changed, 6 insertions(+)

On Mon, Mar 23, 2020 at 3:45 AM Marek Vasut <marex at denx.de> wrote:
>
> This patch prevents an issue where the RX packet might have been
> accessed by the CPU, which now has cached data from the packet in
> the caches and possibly various write buffers, and these data may
> be evicted from the caches into the DRAM while the buffer is also
> written by the DMA.
>
> By invalidating the buffer after the CPU accessed it and before the
> DMA populates the buffer, it is assured that the buffer will not be
> corrupted.
>
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Joe Hershberger <joe.hershberger at ni.com>
> Cc: Patrice Chotard <patrice.chotard at st.com>
> Cc: Patrick Delaunay <patrick.delaunay at st.com>
> Cc: Ramon Fried <rfried.dev at gmail.com>
> Cc: Stephen Warren <swarren at nvidia.com>
> ---
>  drivers/net/dwc_eth_qos.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/dwc_eth_qos.c b/drivers/net/dwc_eth_qos.c
> index e40c461278..7dadb10fe7 100644
> --- a/drivers/net/dwc_eth_qos.c
> +++ b/drivers/net/dwc_eth_qos.c
> @@ -1430,6 +1430,9 @@ static int eqos_free_pkt(struct udevice *dev, uchar *packet, int length)
>         }
>
>         rx_desc = &(eqos->rx_descs[eqos->rx_desc_idx]);
> +
> +       eqos->config->ops->eqos_inval_buffer(packet, length);
> +
>         rx_desc->des0 = (u32)(ulong)packet;
>         rx_desc->des1 = 0;
>         rx_desc->des2 = 0;
> @@ -1492,6 +1495,9 @@ static int eqos_probe_resources_core(struct udevice *dev)
>         }
>         debug("%s: rx_pkt=%p\n", __func__, eqos->rx_pkt);
>
> +       eqos->config->ops->eqos_inval_buffer(eqos->rx_dma_buf,
> +                       EQOS_MAX_PACKET_SIZE * EQOS_DESCRIPTORS_RX);
> +
>         debug("%s: OK\n", __func__);
>         return 0;
>
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>