[PATCH 1/1] net: ftgmac100: Fix Aspeed ast2600 TX hang issue

[Dylan Hung]

> -----Original Message-----
> From: Joel Stanley [mailto:joel at jms.id.au]
> Sent: Thursday, October 15, 2020 6:31 AM
> To: Dylan Hung <dylan_hung at aspeedtech.com>
> Cc: David S . Miller <davem at davemloft.net>; Jakub Kicinski
> <kuba at kernel.org>; netdev at vger.kernel.org; Linux Kernel Mailing List
> <linux-kernel at vger.kernel.org>; Po-Yu Chuang <ratbert at faraday-tech.com>;
> linux-aspeed <linux-aspeed at lists.ozlabs.org>; OpenBMC Maillist
> <openbmc at lists.ozlabs.org>; BMC-SW <BMC-SW at aspeedtech.com>
> Subject: Re: [PATCH 1/1] net: ftgmac100: Fix Aspeed ast2600 TX hang issue
> 
> On Wed, 14 Oct 2020 at 13:32, Dylan Hung <dylan_hung at aspeedtech.com>
> wrote:
> > > > The new HW arbitration feature on Aspeed ast2600 will cause MAC TX
> > > > to hang when handling scatter-gather DMA.  Disable the problematic
> > > > feature by setting MAC register 0x58 bit28 and bit27.
> > >
> > > Hi Dylan,
> > >
> > > What are the symptoms of this issue? We are seeing this on our systems:
> > >
> > > [29376.090637] WARNING: CPU: 0 PID: 9 at net/sched/sch_generic.c:442
> > > dev_watchdog+0x2f0/0x2f4
> > > [29376.099898] NETDEV WATCHDOG: eth0 (ftgmac100): transmit queue 0
> > > timed out
> > >
> >
> > May I know your soc version? This issue happens on ast2600 version A1.
> The registers to fix this issue are meaningless/reserved on A0 chip, so it is
> okay to set them on either A0 or A1.
> 
> We are running the A1. All of our A0 parts have been replaced with A1.
> 
> > I was encountering this issue when I was running the iperf TX test.  The
> symptom is the TX descriptors are consumed, but no complete packet is sent
> out.
> 
> What parameters are you using for iperf? I did a lot of testing with
> iperf3 (and stress-ng running at the same time) and couldn't reproduce the
> error.
> 

I simply use "iperf -c <server ip>" on ast2600.  It is very easy to reproduce. I append the log below:
Noticed that this issue only happens when HW scatter-gather (NETIF_F_SG) is on.

[AST /]$ iperf3 -c 192.168.100.89
Connecting to host 192.168.100.89, port 5201
[  4] local 192.168.100.45 port 45346 connected to 192.168.100.89 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  44.8 MBytes   375 Mbits/sec    2   1.43 KBytes
[  4]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec    2   1.43 KBytes
[  4]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec    0   1.43 KBytes
[  4]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec    1   1.43 KBytes
[  4]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec    0   1.43 KBytes
^C[  4]   5.00-5.88   sec  0.00 Bytes  0.00 bits/sec    0   1.43 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-5.88   sec  44.8 MBytes  64.0 Mbits/sec    5             sender
[  4]   0.00-5.88   sec  0.00 Bytes  0.00 bits/sec                  receiver
iperf3: interrupt - the client has terminated

> We could only reproduce it when performing other functions, such as
> debugging/booting the host processor.
> 
Could it be another issue?

> > > > +/*
> > > > + * test mode control register
> > > > + */
> > > > +#define FTGMAC100_TM_RQ_TX_VALID_DIS (1 << 28) #define
> > > > +FTGMAC100_TM_RQ_RR_IDLE_PREV (1 << 27) #define
> > > > +FTGMAC100_TM_DEFAULT
> > > \
> > > > +       (FTGMAC100_TM_RQ_TX_VALID_DIS |
> > > FTGMAC100_TM_RQ_RR_IDLE_PREV)
> > >
> > > Will aspeed issue an updated datasheet with this register documented?
> 
> Did you see this question?
> 
Sorry, I missed this question.  Aspeed will update the datasheet accordingly.

> Cheers,
> 
> Joel