[Intel-gfx] [PATCH] drm/i915: Request driver probe from an async task

[Jani Nikula]

On Thu, 26 Apr 2018, Imre Deak <imre.deak at intel.com> wrote:
> On Thu, Apr 26, 2018 at 03:41:57PM +0300, David Weinehall wrote:
>> On Fri, Mar 23, 2018 at 08:30:48AM +0000, Chris Wilson wrote:
>> > As we are careful not to register external interfaces before the
>> > internals are brought up, we are not dependent upon a synchronous
>> > probing and can allow ourselves to be probed from a secondary thread
>> > during system bootup. We already do relegate some configuration to
>> > asynchronous tasks (such as setting up the fbdev), now do the entire
>> > probe.
>> > 
>> > References: https://bugs.freedesktop.org/show_bug.cgi?id=105622
>> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>> 
>> LGTM, and still seems to apply cleanly.
>> 
>> Reviewed-by: David Weinehall <david.weinehall at linux.intel.com>
>
> One problem with this is that atm in snd_hdac_i915_init()
> request_module() is expected to return only once the i915 probe function
> has run. With async probing this won't be any more the case.
>
> +Takashi

As I wrote to Yang (Cc'd) in the context of another patch, one approach
that takes care of this would be adding a completion in hdac_i915.c,
waiting for it with a timeout below request_module("i915") in
snd_hdac_i915_init(), and completing it in
hdac_component_master_bind(). How long the timeout should be is anyone's
guess...

BR,
Jani.

>
>> 
>> > Cc: Imre Deak <imre.deak at intel.com>
>> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> > Cc: David Weinehall <david.weinehall at linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/i915_pci.c | 1 +
>> >  1 file changed, 1 insertion(+)
>> > 
>> > diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
>> > index 4364922e935d..be7b03d48229 100644
>> > --- a/drivers/gpu/drm/i915/i915_pci.c
>> > +++ b/drivers/gpu/drm/i915/i915_pci.c
>> > @@ -726,6 +726,7 @@ static struct pci_driver i915_pci_driver = {
>> >  	.probe = i915_pci_probe,
>> >  	.remove = i915_pci_remove,
>> >  	.driver.pm = &i915_pm_ops,
>> > +	.driver.probe_type = PROBE_PREFER_ASYNCHRONOUS,
>> >  };
>> >  
>> >  static int __init i915_init(void)
>> > -- 
>> > 2.16.2
>> > 
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-- 
Jani Nikula, Intel Open Source Technology Center