From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Dylan Hung <dylan_hung@aspeedtech.com>,
davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, ratbert@faraday-tech.com,
linux-aspeed@lists.ozlabs.org, openbmc@lists.ozlabs.org
Cc: BMC-SW@aspeedtech.com
Subject: Re: [PATCH 1/4] ftgmac100: Fix race issue on TX descriptor[0]
Date: Tue, 20 Oct 2020 10:19:25 +1100 [thread overview]
Message-ID: <be7a978c48c9f1c6c29583350dee6168385c3039.camel@kernel.crashing.org> (raw)
In-Reply-To: <20201019085717.32413-2-dylan_hung@aspeedtech.com>
On Mon, 2020-10-19 at 16:57 +0800, Dylan Hung wrote:
> These rules must be followed when accessing the TX descriptor:
>
> 1. A TX descriptor is "cleanable" only when its value is non-zero
> and the owner bit is set to "software"
Can you elaborate ? What is the point of that change ? The owner bit
should be sufficient, why do we need to check other fields ?
> 2. A TX descriptor is "writable" only when its value is zero
> regardless the edotr mask.
Again, why is that ? Can you elaborate ? What race are you trying to
address here ?
Cheers,
Ben.
> Fixes: 52c0cae87465 ("ftgmac100: Remove tx descriptor accessors")
> Signed-off-by: Dylan Hung <dylan_hung@aspeedtech.com>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> drivers/net/ethernet/faraday/ftgmac100.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/net/ethernet/faraday/ftgmac100.c
> b/drivers/net/ethernet/faraday/ftgmac100.c
> index 00024dd41147..7cacbe4aecb7 100644
> --- a/drivers/net/ethernet/faraday/ftgmac100.c
> +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> @@ -647,6 +647,9 @@ static bool ftgmac100_tx_complete_packet(struct
> ftgmac100 *priv)
> if (ctl_stat & FTGMAC100_TXDES0_TXDMA_OWN)
> return false;
>
> + if ((ctl_stat & ~(priv->txdes0_edotr_mask)) == 0)
> + return false;
> +
> skb = priv->tx_skbs[pointer];
> netdev->stats.tx_packets++;
> netdev->stats.tx_bytes += skb->len;
> @@ -756,6 +759,9 @@ static netdev_tx_t
> ftgmac100_hard_start_xmit(struct sk_buff *skb,
> pointer = priv->tx_pointer;
> txdes = first = &priv->txdes[pointer];
>
> + if (le32_to_cpu(txdes->txdes0) & ~priv->txdes0_edotr_mask)
> + goto drop;
> +
> /* Setup it up with the packet head. Don't write the head to
> the
> * ring just yet
> */
> @@ -787,6 +793,10 @@ static netdev_tx_t
> ftgmac100_hard_start_xmit(struct sk_buff *skb,
> /* Setup descriptor */
> priv->tx_skbs[pointer] = skb;
> txdes = &priv->txdes[pointer];
> +
> + if (le32_to_cpu(txdes->txdes0) & ~priv-
> >txdes0_edotr_mask)
> + goto dma_err;
> +
> ctl_stat = ftgmac100_base_tx_ctlstat(priv, pointer);
> ctl_stat |= FTGMAC100_TXDES0_TXDMA_OWN;
> ctl_stat |= FTGMAC100_TXDES0_TXBUF_SIZE(len);
next prev parent reply other threads:[~2020-10-19 23:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 8:57 [PATCH 0/4] fix ftgmac100 issues on aspeed soc Dylan Hung
2020-10-19 8:57 ` [PATCH 1/4] ftgmac100: Fix race issue on TX descriptor[0] Dylan Hung
2020-10-19 23:19 ` Benjamin Herrenschmidt [this message]
2020-10-20 4:13 ` Joel Stanley
2020-10-20 6:23 ` Benjamin Herrenschmidt
2020-10-20 7:13 ` Joel Stanley
2020-10-19 8:57 ` [PATCH 2/4] ftgmac100: Fix missing-poll issue Dylan Hung
2020-10-19 8:57 ` [PATCH 3/4] ftgmac100: Add a dummy read to ensure running sequence Dylan Hung
2020-10-19 23:25 ` Benjamin Herrenschmidt
2020-10-19 8:57 ` [PATCH 4/4] ftgmac100: Restart MAC HW once Dylan Hung
2020-10-19 23:26 ` Benjamin Herrenschmidt
2020-10-20 4:14 ` Joel Stanley
2021-03-12 0:26 ` Joel Stanley
2021-03-12 0:28 ` David Miller
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