[REGRESSION][BISECTED] stmmac: suspend hangs since 1b9707e6f1a9 ("net: stmmac: enable RPS and RBU interrupts")

[REGRESSION][BISECTED] stmmac: suspend hangs since 1b9707e6f1a9 ("net: stmmac: enable RPS and RBU interrupts")

[tresonic]

Hello,
Please bear with me, this is my first time writing to a mailing list...

Since commit 1b9707e6f1a9, suspend (systemctl suspend) causes a full system freeze on my laptop. Fans and keyboard backlight stay powered; the machine is completely unresponsive and requires a hard power-off (holding the power button) to recover. I could not get any kernel output from the hang.

- Reproduces on current master
- git revert 1b9707e6f1a9... on top of master fixes the issue
- Workaround: sudo ip link set eno1 down before suspend avoids the hang entirely; with the interface down, suspend/resume works normally even on the bad commit

Hardware:

64:00.0 Ethernet controller: Motorcomm Microelectronics. YT6801 Gigabit Ethernet Controller (rev 01)
Kernel driver in use: dwmac-motorcomm

[    5.672548] YT8531S Gigabit Ethernet stmmac-6400:00: attached PHY driver (mii_bus:phy_addr=stmmac-6400:00, irq=POLL)
[    5.890940] dwmac-motorcomm 0000:64:00.0 eno1: PHY [stmmac-6400:00] driver [YT8531S Gigabit Ethernet] (irq=POLL)

Thank you,
tresonic

Re: [REGRESSION][BISECTED] stmmac: suspend hangs since 1b9707e6f1a9 ("net: stmmac: enable RPS and RBU interrupts")

[Andrew Lunn]

On Thu, Jul 16, 2026 at 10:10:25PM +0200, tresonic wrote:
> Hello,
> Please bear with me, this is my first time writing to a mailing list...

Thanks for the report. Nice description for a first post. Lots of
useful details.

> Since commit 1b9707e6f1a9, suspend (systemctl suspend) causes a full system freeze on my laptop. Fans and keyboard backlight stay powered; the machine is completely unresponsive and requires a hard power-off (holding the power button) to recover. I could not get any kernel output from the hang.

1b9707e6f1a9 makes in effect 4 changes.

Can you do some testing to see if the changes to
DMA_CHAN_INTR_ABNORMAL or the changes to DMA_CHAN_INTR_ABNORMAL_4_10
break it. Or both, but i think that is unlikely.

Once you know which of those is responsible, can you test to see which
of DMA_CHAN_INTR_ENA_RPS or DMA_CHAN_INTR_ENA_RBU broke it.

It kind of sounds like an interrupt storm, but that is just a
guess. If it is an interrupt storm, it suggests an interrupt is not
being disabled during suspend.

   Andrew

Re: [REGRESSION][BISECTED] stmmac: suspend hangs since 1b9707e6f1a9 ("net: stmmac: enable RPS and RBU interrupts")

[tresonic]

On 7/16/26 11:47 PM, Andrew Lunn wrote:
> On Thu, Jul 16, 2026 at 10:10:25PM +0200, tresonic wrote:
>> Hello,
>> Please bear with me, this is my first time writing to a mailing list...
> 
> Thanks for the report. Nice description for a first post. Lots of
> useful details.
> 
>> Since commit 1b9707e6f1a9, suspend (systemctl suspend) causes a full system freeze on my laptop. Fans and keyboard backlight stay powered; the machine is completely unresponsive and requires a hard power-off (holding the power button) to recover. I could not get any kernel output from the hang.
> 
> 1b9707e6f1a9 makes in effect 4 changes.
> 
> Can you do some testing to see if the changes to
> DMA_CHAN_INTR_ABNORMAL or the changes to DMA_CHAN_INTR_ABNORMAL_4_10
> break it. Or both, but i think that is unlikely.
> 
> Once you know which of those is responsible, can you test to see which
> of DMA_CHAN_INTR_ENA_RPS or DMA_CHAN_INTR_ENA_RBU broke it.
> 
> It kind of sounds like an interrupt storm, but that is just a
> guess. If it is an interrupt storm, it suggests an interrupt is not
> being disabled during suspend.
> 
>    Andrew

I tested the changes as you suggested and it seems DMA_CHAN_INTR_ENA_RPS in DMA_CHAN_INTR_ABNORMAL_4_10 broke it.
With this change on master suspend is working:

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
index 43b036d4e95b..e907142c9ee2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
@@ -121,7 +121,6 @@ static inline u32 dma_chanx_base_addr(const struct dwmac4_addrs *addrs,
                                         DMA_CHAN_INTR_ENA_TIE)
 
 #define DMA_CHAN_INTR_ABNORMAL_4_10    (DMA_CHAN_INTR_ENA_AIE_4_10 | \
-                                        DMA_CHAN_INTR_ENA_RPS | \
                                         DMA_CHAN_INTR_ENA_RBU | \
                                         DMA_CHAN_INTR_ENA_FBE)
 /* DMA default interrupt mask for 4.10a */

tresonic