ath11k: crashes with 1 MSI vector, workaround disable MHI M2 state

[Manivannan Sadhasivam]

Hi Kalle,

On Wed, Dec 16, 2020 at 10:47:18AM +0200, Kalle Valo wrote:
> Hi MHI devs,
> 

[...]

> After extensive debugging from wink he found out that disabling M2 state
> makes the all problems go away:
> 
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -55,12 +55,12 @@ static struct mhi_pm_transitions const dev_state_transitions[] = {
>         },
>         {
>                 MHI_PM_M0,
> -               MHI_PM_M0 | MHI_PM_M2 | MHI_PM_M3_ENTER |
> +               MHI_PM_M0 | MHI_PM_M3_ENTER |
>                 MHI_PM_SYS_ERR_DETECT | MHI_PM_SHUTDOWN_PROCESS |
>                 MHI_PM_LD_ERR_FATAL_DETECT | MHI_PM_FW_DL_ERR
>         },
>         {
> -               MHI_PM_M2,
> +               MHI_PM_M0,
>                 MHI_PM_M0 | MHI_PM_SYS_ERR_DETECT | MHI_PM_SHUTDOWN_PROCESS |
>                 MHI_PM_LD_ERR_FATAL_DETECT
>         },
> 
> And indeed now we have numerous people reporting that with this
> workaround ath11k is stable on their Dell XPS 13 9310 laptops. What on
> earth could cause these kernel crashes/interrupt storms? And why is it
> visible only on Dell laptops? Why does disabling M2 state fix it?
> 

This is related to the ASPM state of the PCIe bus. In the meantime, I'd
suggest to turn off ASPM using "pcie_aspm=off" in the kernel command
line so that the MHI bus stays in M0.

For debugging this issue, can someone enable debug logs for MHI and share
the dmesg output (with ASPM enabled ofc)?

Thanks,
Mani