Re: [PATCH 3/3] drm/i915/fbdev: Flush mode configuration before lastclose

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jun 17, 2016 at 06:54:49PM +0100, Chris Wilson wrote:
> During lastclose, we call intel_fbdev_restore_mode() to switch back to
> the fbcon configuration on return to VT. However, if we have not yet
> finished the asynchronous fbdev initialisation, the current mode will be
> invalid and trigger WARNs upon application.
> 
> Serialise with the outstanding initialisation if the first application
> exits quickly. Note that to hit this in practice requires using an
> unregistered async_domain as otherwise modprobe will force a full
> synchronisation prior to init() completing.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_fbdev.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index 638e420a59cb..a19d621d8815 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -830,6 +830,11 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
>  	if (!ifbdev)
>  		return;
>  
> +	if (ifbdev->cookie) {
> +		async_synchronize_cookie(ifbdev->cookie + 1);
> +		ifbdev->cookie = 0;
> +	}

I kinda wonder whether we shouldn't move all the fbdev async stuff into
the drm helpers. Same request here about adding a small comment about the
+1, with that:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> +
>  	fb_helper = &ifbdev->helper;
>  
>  	ret = drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper);
> -- 
> 2.8.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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