Re: [PATCH 3/3] net: stmmac: Add DWMAC glue layer for Renesas GBETH

Hi Russell,

On Mon, Mar 3, 2025 at 11:19 AM Russell King (Oracle)
[off-list ref] wrote:

On Sun, Mar 02, 2025 at 10:02:15PM +0000, Lad, Prabhakar wrote:

quoted

Hi Russell,

On Sun, Mar 2, 2025 at 9:44 PM Russell King (Oracle)
[off-list ref] wrote:

quoted

On Sun, Mar 02, 2025 at 09:20:49PM +0000, Lad, Prabhakar wrote:

quoted

Hi Russell,

quoted

What is the reason for setting this flag? If it's because of suspend/
resume failures, does my "net: stmmac: fix resume failures due to
RX clock" series solve this for you without requiring this flag?

Ive set this flag based on the configuration supported by this IP.
Unfortunately the platform which I am working on doesn't support s2r
yet so I cannot test suspend/resume path yet. But I do see an issue
when I unload and load just the glue module the DMA reset fails.

Thanks for that feedback - that's a scenario I hadn't considered.

I was trying to avoid having to disable LPI RX clock-stop on suspend by
ensuring that it was enabled at resume time. I think that's valid, but
you've brought up another similar scenario:

- device is brought up, configures RX clock stop
- links with media, negotiates EEE
- driver is unloaded, link doesn't go down, but due to no traffic goes
  into idle, so RX clock is stopped
- driver reloaded, RX clock still stopped, reset fails

I would like to solve that so we can get the power savings from
stopping the clock, but still have reset work when necessary.

I would be happy to test the patches ;)

quoted

I'm guessing that the "DMA reset fails" refers to this path:

stmmac_open() -> __stmmac_open() -> stmmac_hw_setup() ->
stmmac_init_dma_engine() -> stmmac_reset() ?

Yes.

quoted

In other words, when the device is being brought back up
adminsitratively?

What happens if you (replace $if):

# ip li set dev $if down
# ip li set dev $if up

Does that also fail without STMMAC_FLAG_RX_CLK_RUNS_IN_LPI set?

Logs without STMMAC_FLAG_RX_CLK_RUNS_IN_LPI flag set:
--------------------------------------------------------------
root@rzv2h-evk-alpha:~# ip li set dev eth1 down
[   33.606549] renesas-gbeth 15c40000.ethernet eth1: Link is Down
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# ip li set dev eth0 down
[   37.356992] renesas-gbeth 15c30000.ethernet eth0: Link is Down
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# ip li set dev eth1 up
[   43.974803] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-0
[   43.983189] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-1
[   43.991155] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-2
[   43.999128] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-3
[   44.072079] renesas-gbeth 15c40000.ethernet eth1: PHY [stmmac-1:00]
driver [Microchip KSZ9131 Gigabit PHY] (irq=POLL)
[   44.094605] dwmac4: Master AXI performs fixed burst length
[   44.100138] renesas-gbeth 15c40000.ethernet eth1: No Safety
Features support found
[   44.107748] renesas-gbeth 15c40000.ethernet eth1: IEEE 1588-2008
Advanced Timestamp supported
[   44.116725] renesas-gbeth 15c40000.ethernet eth1: registered PTP clock
[   44.123352] renesas-gbeth 15c40000.ethernet eth1: configuring for
phy/rgmii-id link mode
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# ip li set dev eth1[   47.207761] renesas-gbeth
15c40000.ethernet eth1: Link is Up - 1Gbps/Full - flow control off
^C
root@rzv2h-evk-alpha:~# ^C
root@rzv2h-evk-alpha:~# ip li set dev eth0 up
[   55.636722] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-0
[   55.645139] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-1
[   55.653111] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-2
[   55.661073] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-3
[   55.732087] renesas-gbeth 15c30000.ethernet eth0: PHY [stmmac-0:00]
driver [Microchip KSZ9131 Gigabit PHY] (irq=POLL)
[   55.754612] dwmac4: Master AXI performs fixed burst length
[   55.760143] renesas-gbeth 15c30000.ethernet eth0: No Safety
Features support found
[   55.767740] renesas-gbeth 15c30000.ethernet eth0: IEEE 1588-2008
Advanced Timestamp supported
[   55.776705] renesas-gbeth 15c30000.ethernet eth0: registered PTP clock
[   55.783333] renesas-gbeth 15c30000.ethernet eth0: configuring for
phy/rgmii-id link mode
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# [   58.855844] renesas-gbeth 15c30000.ethernet
eth0: tx_clk_stop=1
[   58.861989] renesas-gbeth 15c30000.ethernet eth0: Link is Up -
1Gbps/Full - flow control rx/tx

root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~#

Logs with STMMAC_FLAG_RX_CLK_RUNS_IN_LPI flag set:
--------------------------------------------------------------
root@rzv2h-evk-alpha:~# ip li set dev eth1 down
[   30.053790] renesas-gbeth 15c40000.ethernet eth1: Link is Down
root@rzv2h-evk-alpha:~# ip li set dev eth0 down
[   35.366935] renesas-gbeth 15c30000.ethernet eth0: Link is Down
root@rzv2h-evk-alpha:~# ip li set dev eth1 up
[   40.448563] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-0
[   40.456725] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-1
[   40.464893] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-2
[   40.472840] renesas-gbeth 15c40000.ethernet eth1: Register
MEM_TYPE_PAGE_POOL RxQ-3
[   40.543895] renesas-gbeth 15c40000.ethernet eth1: PHY [stmmac-1:00]
driver [Microchip KSZ9131 Gigabit PHY] (irq=POLL)
[   40.566419] dwmac4: Master AXI performs fixed burst length
[   40.571949] renesas-gbeth 15c40000.ethernet eth1: No Safety
Features support found
[   40.579550] renesas-gbeth 15c40000.ethernet eth1: IEEE 1588-2008
Advanced Timestamp supported
[   40.588505] renesas-gbeth 15c40000.ethernet eth1: registered PTP clock
[   40.595135] renesas-gbeth 15c40000.ethernet eth1: configuring for
phy/rgmii-id link mode
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# [   43.687551] renesas-gbeth 15c40000.ethernet
eth1: Link is Up - 1Gbps/Full - flow control off

root@rzv2h-evk-alpha:~# ip li set dev eth0 up
[   49.644479] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-0
[   49.652719] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-1
[   49.660681] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-2
[   49.669059] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-3
[   49.740011] renesas-gbeth 15c30000.ethernet eth0: PHY [stmmac-0:00]
driver [Microchip KSZ9131 Gigabit PHY] (irq=POLL)
[   49.762518] dwmac4: Master AXI performs fixed burst length
[   49.768057] renesas-gbeth 15c30000.ethernet eth0: No Safety
Features support found
[   49.775655] renesas-gbeth 15c30000.ethernet eth0: IEEE 1588-2008
Advanced Timestamp supported
[   49.784609] renesas-gbeth 15c30000.ethernet eth0: registered PTP clock
[   49.791236] renesas-gbeth 15c30000.ethernet eth0: configuring for
phy/rgmii-id link mode
root@rzv2h-evk-alpha:~#
root@rzv2h-evk-alpha:~# [   52.871635] renesas-gbeth 15c30000.ethernet
eth0: tx_clk_stop=1
[   52.877777] renesas-gbeth 15c30000.ethernet eth0: Link is Up -
1Gbps/Full - flow control rx/tx

I would like to get to the bottom of why this fails for module removal/
insertion, but not for admistratively down/upping the interface.

Removal of your module will unregister the netdev, and part of that
work will bring the netdev administratively down. When re-inserting
the module, that will trigger various userspace events, and it will
be userspace bringing the network interface(s) back up. This should
be no different from administratively down/upping the interface but
it seems you get different behaviour.

I'd like to understand why that is, because at the moment I'm wondering
whether my patches that address the suspend/resume need further work
before I send them - but in order to assess that, I need to work out
why your issue only seems to occur in the module removal/insertion
and not down/up as well as I'd expect.

Please could you investigate this?

Sure I will look into this. Just wanted to check on your platform does
unload/load work OK? Also do you know any specific reason why DMA
reset could be failing so that I can look at it closer.

Cheers,
Prabhakar