diff mbox series

[v2,net-next,02/12] net: mscc: ocelot: only drain extraction queue on error

Message ID 20210213223801.1334216-3-olteanv@gmail.com (mailing list archive)
State Accepted
Commit d7795f8f26d944ede937d750b1804c080edf86c3
Delegated to: Netdev Maintainers
Headers show
Series PTP for DSA tag_ocelot_8021q | expand

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Commit Message

Vladimir Oltean Feb. 13, 2021, 10:37 p.m. UTC 
From: Vladimir Oltean <vladimir.oltean@nxp.com>

It appears that the intention of this snippet of code is to not exit
ocelot_xtr_irq_handler() while in the middle of extracting a frame.
The problem in extracting it word by word is that future extraction
attempts are really easy to get desynchronized, since the IRQ handler
assumes that the first 16 bytes are the IFH, which give further
information about the frame, such as frame length.

But during normal operation, "err" will not be 0, but 4, set from here:

		for (i = 0; i < OCELOT_TAG_LEN / 4; i++) {
			err = ocelot_rx_frame_word(ocelot, grp, true, &ifh[i]);
			if (err != 4)
				break;
		}

		if (err != 4)
			break;

In that case, draining the extraction queue is a no-op. So explicitly
make this code execute only on negative err.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v2:
None.

 drivers/net/ethernet/mscc/ocelot_vsc7514.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Florian Fainelli Feb. 14, 2021, 1:19 a.m. UTC | #1 
On 2/13/2021 14:37, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> It appears that the intention of this snippet of code is to not exit
> ocelot_xtr_irq_handler() while in the middle of extracting a frame.
> The problem in extracting it word by word is that future extraction
> attempts are really easy to get desynchronized, since the IRQ handler
> assumes that the first 16 bytes are the IFH, which give further
> information about the frame, such as frame length.
> 
> But during normal operation, "err" will not be 0, but 4, set from here:
> 
> 		for (i = 0; i < OCELOT_TAG_LEN / 4; i++) {
> 			err = ocelot_rx_frame_word(ocelot, grp, true, &ifh[i]);
> 			if (err != 4)
> 				break;
> 		}
> 
> 		if (err != 4)
> 			break;
> 
> In that case, draining the extraction queue is a no-op. So explicitly
> make this code execute only on negative err.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mscc/ocelot_vsc7514.c b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
index 590297d5e144..d19efbe6ffd3 100644
--- a/drivers/net/ethernet/mscc/ocelot_vsc7514.c
+++ b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
@@ -701,7 +701,7 @@  static irqreturn_t ocelot_xtr_irq_handler(int irq, void *arg)
 		dev->stats.rx_packets++;
 	}
 
-	if (err)
+	if (err < 0)
 		while (ocelot_read(ocelot, QS_XTR_DATA_PRESENT) & BIT(grp))
 			ocelot_read_rix(ocelot, QS_XTR_RD, grp);