Re: [PATCH 2/4] drm/i915: Stop depending upon CONFIG_AGP_INTEL

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jan 27, 2016 at 02:37:59PM +0100, Daniel Vetter wrote:
> The AGP_INTEL driver provides an interface for very old userspace to
> control the GART (though the GART itself was only ever emulated on Intel
> systems). The pci bridge discovery code is also used by the i915.ko
> driver to set up the GTT on old systems, but it does not require the
> old userspace interface. When i915.ko selects the old interface, it
> binds another user to the core GTT routines, and in particular creates a
> second reference to the scratch pages allocated. This hinders resource
> leak debugging for when we unload i915.ko as we want to assert that all
> DMA pages have been released, but we appear to leak because of the
> secondary interface which persists after i915.ko unloads.
> 
> All i915.ko users do not require the old /dev/agpgart interface so stop
> selecting it and simplify our debugging by dropping the historical
> baggage.
> 
> Note that by selecting AGP=n it was already possible to unselect
> AGP_INTEL. But since we've dropped support for any of the AGP stuff
> long ago there's really no point for this any more.

Hmm. There surely was some kind of dependency between intel-agp and i915
which required the former to be builtin when i915 was, and that was the
reason for the kconfig magic IIRC. Not quite sure why I made i915 depend
on AGP and select INTEL_AGP though, instead of just
'depends on (INTEL_AGP || INTEL_AGP=n)'
but I guess there was some reason.

Anyways, after looking at git logs, I guess the dependency was
'extern int intel_agp_enabled' which got killed off in
commit 3bb6ce668663 ("drm/i915: Kill legeacy AGP for gen3 kms")
so perhaps note that in the commit message.

But yeah, with that stuff gone I think this should be fine, so
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> 
> Also note that we still need INTEL_GTT, which is the underlying,
> share, driver for the graphics GART on gen1-5.
  ^^^^^

shared?

> 
> v2: Entirely new commit message (Chris, Ville).
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/i915/Kconfig | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index fcd77b27514d..9aa7d2d98add 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -2,9 +2,7 @@ config DRM_I915
>  	tristate "Intel 8xx/9xx/G3x/G4x/HD Graphics"
>  	depends on DRM
>  	depends on X86 && PCI
> -	depends on (AGP || AGP=n)
>  	select INTEL_GTT
> -	select AGP_INTEL if AGP
>  	select INTERVAL_TREE
>  	# we need shmfs for the swappable backing store, and in particular
>  	# the shmem_readpage() which depends upon tmpfs
> -- 
> 2.5.0

-- 
Ville Syrjälä
Intel OTC
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