Re: [PATCH 1/3] drm/i915/fbdev: Perform async fbdev initialisation much later

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jun 17, 2016 at 06:54:47PM +0100, Chris Wilson wrote:
> Setting up fbdev requires everything ready and registered (in particular
> the connectors). In the next patch, we defer registration of the KMS
> objects and unless we defer setting off fbdev, it may run before they are
> registered and oops.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_dma.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 24b670f72ed4..0127e969a912 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -525,18 +525,6 @@ static int i915_load_modeset_init(struct drm_device *dev)
>  	/* Only enable hotplug handling once the fbdev is fully set up. */
>  	intel_hpd_init(dev_priv);
>  
> -	/*
> -	 * Some ports require correctly set-up hpd registers for detection to
> -	 * work properly (leading to ghost connected connector status), e.g. VGA
> -	 * on gm45.  Hence we can only set up the initial fbdev config after hpd
> -	 * irqs are fully enabled. Now we should scan for the initial config
> -	 * only once hotplug handling is enabled, but due to screwed-up locking
> -	 * around kms/fbdev init we can't protect the fdbev initial config
> -	 * scanning against hotplug events. Hence do this first and ignore the
> -	 * tiny window where we will loose hotplug notifactions.
> -	 */
> -	intel_fbdev_initial_config_async(dev);
> -
>  	drm_kms_helper_poll_init(dev);
>  
>  	return 0;
> @@ -1413,6 +1401,18 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
>  		intel_gpu_ips_init(dev_priv);
>  
>  	i915_audio_component_init(dev_priv);
> +
> +	/*
> +	 * Some ports require correctly set-up hpd registers for detection to
> +	 * work properly (leading to ghost connected connector status), e.g. VGA
> +	 * on gm45.  Hence we can only set up the initial fbdev config after hpd
> +	 * irqs are fully enabled. Now we should scan for the initial config
> +	 * only once hotplug handling is enabled, but due to screwed-up locking
> +	 * around kms/fbdev init we can't protect the fdbev initial config
> +	 * scanning against hotplug events. Hence do this first and ignore the
> +	 * tiny window where we will loose hotplug notifactions.
> +	 */

Comment seems bogus now - we're definitely _after_ hotplug enabling now.
Wrt fbdev locking: Thierry Redding is working on patches to arbitrarily
delay fbdev setup until the first sink shows up. Which will fix the
locking. I'd remove all that noise and just keep the part that explains
why we need hpd enabled first. With that fixed:

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

> +	intel_fbdev_initial_config_async(dev);
>  }
>  
>  /**
> -- 
> 2.8.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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