Re: [PATCH] drm/i915/gsc: mei interrupt top half should be in irq disabled context

[Jani Nikula]

On Fri, 25 Apr 2025, Junxiao Chang <junxiao.chang@xxxxxxxxx> wrote:
> MEI GSC interrupt comes from i915. It has top half and bottom half.
> Top half is called from i915 interrupt handler. It should be in
> irq disabled context.
>
> With RT kernel, by default i915 IRQ handler is in threaded IRQ. MEI GSC
> top half might be in threaded IRQ context. generic_handle_irq_safe API
> could be called from either IRQ or process context, it disables local
> IRQ then calls MEI GSC interrupt top half.
>
> This change fixes A380/A770 GPU boot hang issue with RT kernel.
>
> Fixes: 1e3dc1d8622b ("drm/i915/gsc: add gsc as a mei auxiliary device")
> Tested-by: Furong Zhou <furong.zhou@xxxxxxxxx>
> Suggested-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Junxiao Chang <junxiao.chang@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/gt/intel_gsc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gsc.c b/drivers/gpu/drm/i915/gt/intel_gsc.c
> index 1e925c75fb080..a099d885508ac 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gsc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gsc.c
> @@ -284,7 +284,9 @@ static void gsc_irq_handler(struct intel_gt *gt, unsigned int intf_id)
>  	if (gt->gsc.intf[intf_id].irq < 0)
>  		return;
>  
> -	ret = generic_handle_irq(gt->gsc.intf[intf_id].irq);
> +	/* It can be called in both irq context and in thread context */

What is "It" in this case?

> +	ret = generic_handle_irq_safe(gt->gsc.intf[intf_id].irq);
> +
>  	if (ret)
>  		gt_err_ratelimited(gt, "error handling GSC irq: %d\n", ret);
>  }

-- 
Jani Nikula, Intel