net: thunderbolt: Enable e2e flow control in two direction

[PATCH] net: thunderbolt: Enable e2e flow control in two direction

Posted by zhangjianrong 3 months, 2 weeks ago

According to USB4 specification, if E2E flow control is disabled for
the Transmit Descriptor Ring, the Host Interface Adapter Layer shall
not require any credits to be available before transmitting a Tunneled
Packet from this Transmit Descriptor Ring, so e2e flow control should
be enabled in two direction.

Signed-off-by: zhangjianrong <zhangjianrong5@huawei.com>
---
 drivers/net/thunderbolt/main.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 0a53ec293d04..643cf67840b5 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -924,8 +924,12 @@ static int tbnet_open(struct net_device *dev)
 
 	netif_carrier_off(dev);
 
-	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE,
-				RING_FLAG_FRAME);
+	flags = RING_FLAG_FRAME;
+	/* Only enable full E2E if the other end supports it too */
+	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
+		flags |= RING_FLAG_E2E;
+
+	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags);
 	if (!ring) {
 		netdev_err(dev, "failed to allocate Tx ring\n");
 		return -ENOMEM;
@@ -944,11 +948,6 @@ static int tbnet_open(struct net_device *dev)
 	sof_mask = BIT(TBIP_PDF_FRAME_START);
 	eof_mask = BIT(TBIP_PDF_FRAME_END);
 
-	flags = RING_FLAG_FRAME;
-	/* Only enable full E2E if the other end supports it too */
-	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
-		flags |= RING_FLAG_E2E;
-
 	ring = tb_ring_alloc_rx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags,
 				net->tx_ring.ring->hop, sof_mask,
 				eof_mask, tbnet_start_poll, net);
-- 
2.34.1

Re: [PATCH] net: thunderbolt: Enable e2e flow control in two direction

Posted by Mika Westerberg 3 months, 2 weeks ago

Hi,

Perhaps $subject:

net: thunderbolt: Enable end-to-end flow control also in transmit

or so.

On Tue, Jun 24, 2025 at 05:32:05PM +0800, zhangjianrong wrote:
> According to USB4 specification, if E2E flow control is disabled for
> the Transmit Descriptor Ring, the Host Interface Adapter Layer shall
> not require any credits to be available before transmitting a Tunneled
> Packet from this Transmit Descriptor Ring, so e2e flow control should
> be enabled in two direction.

be enabled in both directions.

> Signed-off-by: zhangjianrong <zhangjianrong5@huawei.com>

Good finding, though.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

> ---
>  drivers/net/thunderbolt/main.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
> index 0a53ec293d04..643cf67840b5 100644
> --- a/drivers/net/thunderbolt/main.c
> +++ b/drivers/net/thunderbolt/main.c
> @@ -924,8 +924,12 @@ static int tbnet_open(struct net_device *dev)
>  
>  	netif_carrier_off(dev);
>  
> -	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE,
> -				RING_FLAG_FRAME);
> +	flags = RING_FLAG_FRAME;
> +	/* Only enable full E2E if the other end supports it too */
> +	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
> +		flags |= RING_FLAG_E2E;
> +
> +	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags);
>  	if (!ring) {
>  		netdev_err(dev, "failed to allocate Tx ring\n");
>  		return -ENOMEM;
> @@ -944,11 +948,6 @@ static int tbnet_open(struct net_device *dev)
>  	sof_mask = BIT(TBIP_PDF_FRAME_START);
>  	eof_mask = BIT(TBIP_PDF_FRAME_END);
>  
> -	flags = RING_FLAG_FRAME;
> -	/* Only enable full E2E if the other end supports it too */
> -	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
> -		flags |= RING_FLAG_E2E;
> -
>  	ring = tb_ring_alloc_rx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags,
>  				net->tx_ring.ring->hop, sof_mask,
>  				eof_mask, tbnet_start_poll, net);
> -- 
> 2.34.1