[Intel-gfx] [PATCH 3/4] agp/intel-gtt: Only register fake agp driver for gen1

[Ville Syrjälä]

On Wed, Jan 27, 2016 at 02:38:00PM +0100, Daniel Vetter wrote:
> The fake agp driver for the intel graphics gart is only needed for ums
> support. And we ditched that a long time ago:
> 
> commit 03dae59c72ffffd8ef6e005f48ba356c863e0587
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Wed Jul 23 16:27:25 2014 +0200
> 
>     drm/i915: Ditch UMS config option
> 
> With this there's no longer the problem that 2 drivers (fake agp
> driver and the drm/i915 driver) fight over the same piece, which fixes
> apparent dma leaks detected by CONFIG_DMA_API_DEBUG.
> 
> Note that the leak isn't real since intel-gtt refcounts and will tear
> down eventually. But the debug code assumes that when the i915 driver
> unbinds from the pci device everything should be gone. Which isn't the
> case if we have intel-agp enabled - userspace might need it. But by
> ditching this intel-gtt setup and teardown is completely tied to the
> livetime of the "real" driver.
> 
> While at it untangle the init ordering a bit - the fake agp wouldn't
> be initialized correctly if i915.ko loads first. Which isn't a problem
> since when i915 loads in kms mode you won't need the fake agp support
> needed by the ums driver ...
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93793
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/char/agp/intel-gtt.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
> index e657f989745e..aef87fdbd187 100644
> --- a/drivers/char/agp/intel-gtt.c
> +++ b/drivers/char/agp/intel-gtt.c
> @@ -1348,16 +1348,6 @@ int intel_gmch_probe(struct pci_dev *bridge_pdev, struct pci_dev *gpu_pdev,
>  {
>  	int i, mask;
>  
> -	/*
> -	 * Can be called from the fake agp driver but also directly from
> -	 * drm/i915.ko. Hence we need to check whether everything is set up
> -	 * already.
> -	 */
> -	if (intel_private.driver) {
> -		intel_private.refcount++;
> -		return 1;
> -	}
> -
>  	for (i = 0; intel_gtt_chipsets[i].name != NULL; i++) {
>  		if (gpu_pdev) {
>  			if (gpu_pdev->device ==
> @@ -1378,16 +1368,26 @@ int intel_gmch_probe(struct pci_dev *bridge_pdev, struct pci_dev *gpu_pdev,
>  	if (!intel_private.driver)
>  		return 0;
>  
> -	intel_private.refcount++;
> -
>  #if IS_ENABLED(CONFIG_AGP_INTEL)
>  	if (bridge) {
> +		if (INTEL_GTT_GEN > 1)
> +			return 0;

So if this happens first, we set up intel_private.driver but leave the
refcount at 0. Then i915 loads and we set up intel_private.driver again,
and bump the refcount to 0. Well, we should end up pointing
intel_privatee.driver at the same thing both times so not really a
problem I suppose.

So yeah, I think this ought to work
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

I guess we could also trim the gen>=2 gmch pci ids from the agp
driver's pci id table, to avoid even probing it.

> +
>  		bridge->driver = &intel_fake_agp_driver;
>  		bridge->dev_private_data = &intel_private;
>  		bridge->dev = bridge_pdev;
>  	}
>  #endif
>  
> +
> +	/*
> +	 * Can be called from the fake agp driver but also directly from
> +	 * drm/i915.ko. Hence we need to check whether everything is set up
> +	 * already.
> +	 */
> +	if (intel_private.refcount++)
> +		return 1;
> +
>  	intel_private.bridge_dev = pci_dev_get(bridge_pdev);
>  
>  	dev_info(&bridge_pdev->dev, "Intel %s Chipset\n", intel_gtt_chipsets[i].name);
> -- 
> 2.5.0
> 
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-- 
Ville Syrjälä
Intel OTC