[4/6] net: dwc_eth_qos: Invalidate RX descriptor before reading

The current code polls the RX desciptor ring for new packets by reading
the RX descriptor status. This works by accident, as the RX descriptors
are often in non-cacheable memory. However, the driver does support use
of RX descriptors in cacheable memory.

This patch adds a missing RX descriptor invalidation, which assures the
CPU will read a fresh copy of the RX descriptor instead of a cached one.

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 | 1 +
 1 file changed, 1 insertion(+)

On Mon, Mar 23, 2020 at 3:45 AM Marek Vasut <marex at denx.de> wrote:
>
> The current code polls the RX desciptor ring for new packets by reading
> the RX descriptor status. This works by accident, as the RX descriptors
> are often in non-cacheable memory. However, the driver does support use
> of RX descriptors in cacheable memory.
>
> This patch adds a missing RX descriptor invalidation, which assures the
> CPU will read a fresh copy of the RX descriptor instead of a cached one.
>
> 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 | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/dwc_eth_qos.c b/drivers/net/dwc_eth_qos.c
> index 66cc301c8c..e40c461278 100644
> --- a/drivers/net/dwc_eth_qos.c
> +++ b/drivers/net/dwc_eth_qos.c
> @@ -1397,6 +1397,7 @@ static int eqos_recv(struct udevice *dev, int flags, uchar **packetp)
>         debug("%s(dev=%p, flags=%x):\n", __func__, dev, flags);
>
>         rx_desc = &(eqos->rx_descs[eqos->rx_desc_idx]);
> +       eqos->config->ops->eqos_inval_desc(rx_desc);
>         if (rx_desc->des3 & EQOS_DESC3_OWN) {
>                 debug("%s: RX packet not available\n", __func__);
>                 return -EAGAIN;
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>