[Skiboot] [PATCH] hmi: Clear unknown debug trigger

[Michael Neuling]

Stewart,

Hold off on merging this.  I think queuing up an event to linux is the wrong
thing to do as if you get too many of these before linux boots, we fill the opal
msg queue.

I'll repost once we get some more testing.

Mikey

On Fri, 2018-05-04 at 14:06 +1000, Michael Neuling wrote:
> From: Ryan Grimm <grimm at linux.vnet.ibm.com>
> 
> On some systems, seeing hangs like this when Linux starts:
>   [ 170.027252763,5] OCC: All Chip Rdy after 0 ms
>   [ 170.062930145,5] INIT: Starting kernel at 0x20011000, fdt at 0x30ae0530
> 366247 bytes)
>   [ 171.238270428,5] OPAL: Switch to little-endian OS
> 
> If you look at the in memory skiboot console (or do 'nvram -p
> ibm,skiboot --update-config log-level-driver=7') we see the console get
> spammed with:
>   [ 5209.109790675,7] HMI: Received HMI interrupt: HMER = 0x0000400000000000
>   [ 5209.109792716,7] HMI: Received HMI interrupt: HMER = 0x0000400000000000
>   [ 5209.109794695,7] HMI: Received HMI interrupt: HMER = 0x0000400000000000
>   [ 5209.109796689,7] HMI: Received HMI interrupt: HMER = 0x0000400000000000
> 
> We're taking the debug trigger (bit 17) early on, before the
> hmi_debug_trigger function in the kernel is set up.
> 
> This clears the HMI in Skiboot and reports to the kernel instead of
> bringing down the machine.
> 
> Signed-off-by: Ryan Grimm <grimm at linux.vnet.ibm.com>
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> ---
>  core/hmi.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/core/hmi.c b/core/hmi.c
> index bd0fc13b80..9e80c54f47 100644
> --- a/core/hmi.c
> +++ b/core/hmi.c
> @@ -1258,6 +1258,16 @@ static int handle_hmi_exception(uint64_t hmer, struct
> OpalHMIEvent *hmi_evt,
>  			queue_hmi_event(hmi_evt, recover, out_flags);
>  		}
>  	}
> +	if (hmer & SPR_HMER_TRIG_FIR_HMI) {
> +		hmer &= ~SPR_HMER_TRIG_FIR_HMI;
> +
> +		hmi_print_debug("Clearing unknown debug trigger", hmer);
> +		if (hmi_evt) {
> +			hmi_evt->severity = OpalHMI_SEV_NO_ERROR;
> +			hmi_evt->type = OpalHMI_ERROR_DEBUG_TRIG_FIR,
> +				queue_hmi_event(hmi_evt, recover, out_flags);
> +		}
> +	}
>  
>  	if (recover == 0)
>  		disable_fast_reboot("Unrecoverable HMI");