[PATCH] net: ftgmac100: Fix missing TX-poll issue
joel at jms.id.au
Mon Oct 19 19:57:03 AEDT 2020
On Mon, 19 Oct 2020 at 07:39, Dylan Hung <dylan_hung at aspeedtech.com> wrote:
> The cpu accesses the register and the memory via different bus/path on
> aspeed soc. So we can not guarantee that the tx-poll command
Just the 2600, or other versions too?
> (register access) is always behind the tx descriptor (memory). In other
> words, the HW may start working even the data is not yet ready. By
even if the
> adding a dummy read after the last data write, we can ensure the data
> are pushed to the memory, then guarantee the processing sequence
> Signed-off-by: Dylan Hung <dylan_hung at aspeedtech.com>
> drivers/net/ethernet/faraday/ftgmac100.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
> index 00024dd41147..9a99a87f29f3 100644
> --- a/drivers/net/ethernet/faraday/ftgmac100.c
> +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> @@ -804,7 +804,8 @@ static netdev_tx_t ftgmac100_hard_start_xmit(struct sk_buff *skb,
> * before setting the OWN bit on the first descriptor.
> - first->txdes0 = cpu_to_le32(f_ctl_stat);
> + WRITE_ONCE(first->txdes0, cpu_to_le32(f_ctl_stat));
> + READ_ONCE(first->txdes0);
I understand what you're trying to do here, but I'm not sure that this
is the correct way to go about it.
It does cause the compiler to produce a store and then a load.
> /* Update next TX pointer */
> priv->tx_pointer = pointer;
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