Re: [PATCH 4/4] drm/tegra: Refactor IOMMU attach/detach

[Dmitry Osipenko <digetx@gmail.com>]

On 04.05.2018 18:10, Thierry Reding wrote:
> On Fri, May 04, 2018 at 05:23:42PM +0300, Dmitry Osipenko wrote:
>> On 04.05.2018 16:37, Thierry Reding wrote:
>>> From: Thierry Reding <treding@nvidia.com>
>>>
>>> Attaching to and detaching from an IOMMU uses the same code sequence in
>>> every driver, so factor it out into separate helpers.
>>>
>>> Signed-off-by: Thierry Reding <treding@nvidia.com>
>>> ---
>>>  drivers/gpu/drm/tegra/dc.c   | 42 ++++++------------------------------
>>>  drivers/gpu/drm/tegra/drm.c  | 42 ++++++++++++++++++++++++++++++++++++
>>>  drivers/gpu/drm/tegra/drm.h  |  4 ++++
>>>  drivers/gpu/drm/tegra/gr2d.c | 32 +++++++--------------------
>>>  drivers/gpu/drm/tegra/gr3d.c | 31 ++++++--------------------
>>>  5 files changed, 68 insertions(+), 83 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
>>> index c843f11043db..3e7ec3937346 100644
>>> --- a/drivers/gpu/drm/tegra/dc.c
>>> +++ b/drivers/gpu/drm/tegra/dc.c
>>> @@ -1837,21 +1837,11 @@ static int tegra_dc_init(struct host1x_client *client)
>>>  	if (!dc->syncpt)
>>>  		dev_warn(dc->dev, "failed to allocate syncpoint\n");
>>>  
>>> -	if (tegra->domain) {
>>> -		dc->group = iommu_group_get(client->dev);
>>> -
>>> -		if (dc->group && dc->group != tegra->group) {
>>> -			err = iommu_attach_group(tegra->domain, dc->group);
>>> -			if (err < 0) {
>>> -				dev_err(dc->dev,
>>> -					"failed to attach to domain: %d\n",
>>> -					err);
>>> -				iommu_group_put(dc->group);
>>> -				return err;
>>> -			}
>>> -
>>> -			tegra->group = dc->group;
>>> -		}
>>> +	dc->group = host1x_client_iommu_attach(client, true);
>>> +	if (IS_ERR(dc->group)) {
>>> +		err = PTR_ERR(dc->group);
>>> +		dev_err(client->dev, "failed to attach to domain: %d\n", err);
>>> +		return err;
>>>  	}
>>>  
>>>  	if (dc->soc->wgrps)
>>> @@ -1916,15 +1906,7 @@ static int tegra_dc_init(struct host1x_client *client)
>>>  	if (!IS_ERR(primary))
>>>  		drm_plane_cleanup(primary);
>>>  
>>> -	if (dc->group) {
>>> -		if (dc->group == tegra->group) {
>>> -			iommu_detach_group(tegra->domain, dc->group);
>>> -			tegra->group = NULL;
>>> -		}
>>> -
>>> -		iommu_group_put(dc->group);
>>> -	}
>>> -
>>> +	host1x_client_iommu_detach(client, dc->group);
>>>  	host1x_syncpt_free(dc->syncpt);
>>>  
>>>  	return err;
>>> @@ -1932,9 +1914,7 @@ static int tegra_dc_init(struct host1x_client *client)
>>>  
>>>  static int tegra_dc_exit(struct host1x_client *client)
>>>  {
>>> -	struct drm_device *drm = dev_get_drvdata(client->parent);
>>>  	struct tegra_dc *dc = host1x_client_to_dc(client);
>>> -	struct tegra_drm *tegra = drm->dev_private;
>>>  	int err;
>>>  
>>>  	devm_free_irq(dc->dev, dc->irq, dc);
>>> @@ -1945,15 +1925,7 @@ static int tegra_dc_exit(struct host1x_client *client)
>>>  		return err;
>>>  	}
>>>  
>>> -	if (dc->group) {
>>> -		if (dc->group == tegra->group) {
>>> -			iommu_detach_group(tegra->domain, dc->group);
>>> -			tegra->group = NULL;
>>> -		}
>>> -
>>> -		iommu_group_put(dc->group);
>>> -	}
>>> -
>>> +	host1x_client_iommu_detach(client, dc->group);
>>>  	host1x_syncpt_free(dc->syncpt);
>>>  
>>>  	return 0;
>>> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
>>> index 7afe2f635f74..bc1008305e1e 100644
>>> --- a/drivers/gpu/drm/tegra/drm.c
>>> +++ b/drivers/gpu/drm/tegra/drm.c
>>> @@ -1114,6 +1114,48 @@ int tegra_drm_unregister_client(struct tegra_drm *tegra,
>>>  	return 0;
>>>  }
>>>  
>>> +struct iommu_group *host1x_client_iommu_attach(struct host1x_client *client,
>>> +					       bool shared)
>>> +{
>>> +	struct drm_device *drm = dev_get_drvdata(client->parent);
>>> +	struct tegra_drm *tegra = drm->dev_private;
>>> +	struct iommu_group *group = NULL;
>>> +	int err;
>>> +
>>> +	if (tegra->domain) {
>>> +		group = iommu_group_get(client->dev);
>>> +
>>> +		if (group && (!shared || (shared && (group != tegra->group)))) {
>>> +			err = iommu_attach_group(tegra->domain, group);
>>> +			if (err < 0) {
>>> +				iommu_group_put(group);
>>> +				return ERR_PTR(err);
>>> +			}
>>> +
>>> +			if (shared && !tegra->group)
>>> +				tegra->group = group;
>>> +		}
>>> +	}
>>> +
>>> +	return group;
>>> +}
>>> +
>>> +void host1x_client_iommu_detach(struct host1x_client *client,
>>> +				struct iommu_group *group)
>>> +{
>>> +	struct drm_device *drm = dev_get_drvdata(client->parent);
>>> +	struct tegra_drm *tegra = drm->dev_private;
>>> +
>>> +	if (group) {
>>> +		if (group == tegra->group) {
>>> +			iommu_detach_group(tegra->domain, group);
>>> +			tegra->group = NULL;
>>> +		}
>>> +
>>> +		iommu_group_put(group);
>>> +	}
>>> +}
>>> +
>>>  void *tegra_drm_alloc(struct tegra_drm *tegra, size_t size, dma_addr_t *dma)
>>>  {
>>>  	struct iova *alloc;
>>> diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
>>> index 4f41aaec8530..fe263cf58f34 100644
>>> --- a/drivers/gpu/drm/tegra/drm.h
>>> +++ b/drivers/gpu/drm/tegra/drm.h
>>> @@ -110,6 +110,10 @@ int tegra_drm_register_client(struct tegra_drm *tegra,
>>>  			      struct tegra_drm_client *client);
>>>  int tegra_drm_unregister_client(struct tegra_drm *tegra,
>>>  				struct tegra_drm_client *client);
>>> +struct iommu_group *host1x_client_iommu_attach(struct host1x_client *client,
>>> +					       bool shared);
>>> +void host1x_client_iommu_detach(struct host1x_client *client,
>>> +				struct iommu_group *group);
>>>  
>>>  int tegra_drm_init(struct tegra_drm *tegra, struct drm_device *drm);
>>>  int tegra_drm_exit(struct tegra_drm *tegra);
>>> diff --git a/drivers/gpu/drm/tegra/gr2d.c b/drivers/gpu/drm/tegra/gr2d.c
>>> index 0b42e99da8ad..2cd0f66c8aa9 100644
>>> --- a/drivers/gpu/drm/tegra/gr2d.c
>>> +++ b/drivers/gpu/drm/tegra/gr2d.c
>>> @@ -32,7 +32,6 @@ static int gr2d_init(struct host1x_client *client)
>>>  	struct tegra_drm_client *drm = host1x_to_drm_client(client);
>>>  	struct drm_device *dev = dev_get_drvdata(client->parent);
>>>  	unsigned long flags = HOST1X_SYNCPT_HAS_BASE;
>>> -	struct tegra_drm *tegra = dev->dev_private;
>>>  	struct gr2d *gr2d = to_gr2d(drm);
>>>  	int err;
>>>  
>>> @@ -47,22 +46,14 @@ static int gr2d_init(struct host1x_client *client)
>>>  		goto put;
>>>  	}
>>>  
>>> -	if (tegra->domain) {
>>> -		gr2d->group = iommu_group_get(client->dev);
>>> -
>>> -		if (gr2d->group) {
>>> -			err = iommu_attach_group(tegra->domain, gr2d->group);
>>> -			if (err < 0) {
>>> -				dev_err(client->dev,
>>> -					"failed to attach to domain: %d\n",
>>> -					err);
>>> -				iommu_group_put(gr2d->group);
>>> -				goto free;
>>> -			}
>>> -		}
>>> +	gr2d->group = host1x_client_iommu_attach(client, false);
>>> +	if (IS_ERR(gr2d->group)) {
>>> +		err = PTR_ERR(gr2d->group);
>>> +		dev_err(client->dev, "failed to attach to domain: %d\n", err);
>>> +		goto free;
>>>  	}
>>>  
>>> -	err = tegra_drm_register_client(tegra, drm);
>>> +	err = tegra_drm_register_client(dev->dev_private, drm);
>>>  	if (err < 0) {
>>>  		dev_err(client->dev, "failed to register client: %d\n", err);
>>>  		goto detach;
>>> @@ -71,10 +62,7 @@ static int gr2d_init(struct host1x_client *client)
>>>  	return 0;
>>>  
>>>  detach:
>>> -	if (gr2d->group) {
>>> -		iommu_detach_group(tegra->domain, gr2d->group);
>>> -		iommu_group_put(gr2d->group);
>>> -	}
>>> +	host1x_client_iommu_detach(client, gr2d->group);
>>>  free:
>>>  	host1x_syncpt_free(client->syncpts[0]);
>>>  put:
>>> @@ -94,14 +82,10 @@ static int gr2d_exit(struct host1x_client *client)
>>>  	if (err < 0)
>>>  		return err;
>>>  
>>> +	host1x_client_iommu_detach(client, gr2d->group);
>>>  	host1x_syncpt_free(client->syncpts[0]);
>>>  	host1x_channel_put(gr2d->channel);
>>>  
>>> -	if (gr2d->group) {
>>> -		iommu_detach_group(tegra->domain, gr2d->group);
>>> -		iommu_group_put(gr2d->group);
>>> -	}
>>> -
>>>  	return 0;
>>>  }
>>>  
>>> diff --git a/drivers/gpu/drm/tegra/gr3d.c b/drivers/gpu/drm/tegra/gr3d.c
>>> index e129f1afff33..98e3c67d0fb5 100644
>>> --- a/drivers/gpu/drm/tegra/gr3d.c
>>> +++ b/drivers/gpu/drm/tegra/gr3d.c
>>> @@ -42,7 +42,6 @@ static int gr3d_init(struct host1x_client *client)
>>>  	struct tegra_drm_client *drm = host1x_to_drm_client(client);
>>>  	struct drm_device *dev = dev_get_drvdata(client->parent);
>>>  	unsigned long flags = HOST1X_SYNCPT_HAS_BASE;
>>> -	struct tegra_drm *tegra = dev->dev_private;
>>>  	struct gr3d *gr3d = to_gr3d(drm);
>>>  	int err;
>>>  
>>> @@ -56,19 +55,11 @@ static int gr3d_init(struct host1x_client *client)
>>>  		goto put;
>>>  	}
>>>  
>>> -	if (tegra->domain) {
>>> -		gr3d->group = iommu_group_get(client->dev);
>>> -
>>> -		if (gr3d->group) {
>>> -			err = iommu_attach_group(tegra->domain, gr3d->group);
>>> -			if (err < 0) {
>>> -				dev_err(client->dev,
>>> -					"failed to attach to domain: %d\n",
>>> -					err);
>>> -				iommu_group_put(gr3d->group);
>>> -				goto free;
>>> -			}
>>> -		}
>>> +	gr3d->group = host1x_client_iommu_attach(client, false);
>>> +	if (IS_ERR(gr3d->group)) {
>>> +		err = PTR_ERR(gr3d->group);
>>> +		dev_err(client->dev, "failed to attach to domain: %d\n", err);
>>> +		goto free;
>>>  	}
>>>  
>>>  	err = tegra_drm_register_client(dev->dev_private, drm);
>>> @@ -80,10 +71,7 @@ static int gr3d_init(struct host1x_client *client)
>>>  	return 0;
>>>  
>>>  detach:
>>> -	if (gr3d->group) {
>>> -		iommu_detach_group(tegra->domain, gr3d->group);
>>> -		iommu_group_put(gr3d->group);
>>> -	}
>>> +	host1x_client_iommu_detach(client, gr3d->group);
>>>  free:
>>>  	host1x_syncpt_free(client->syncpts[0]);
>>>  put:
>>> @@ -95,7 +83,6 @@ static int gr3d_exit(struct host1x_client *client)
>>>  {
>>>  	struct tegra_drm_client *drm = host1x_to_drm_client(client);
>>>  	struct drm_device *dev = dev_get_drvdata(client->parent);
>>> -	struct tegra_drm *tegra = dev->dev_private;
>>>  	struct gr3d *gr3d = to_gr3d(drm);
>>>  	int err;
>>>  
>>> @@ -103,14 +90,10 @@ static int gr3d_exit(struct host1x_client *client)
>>>  	if (err < 0)
>>>  		return err;
>>>  
>>> +	host1x_client_iommu_detach(client, gr3d->group);
>>>  	host1x_syncpt_free(client->syncpts[0]);
>>>  	host1x_channel_put(gr3d->channel);
>>>  
>>> -	if (gr3d->group) {
>>> -		iommu_detach_group(tegra->domain, gr3d->group);
>>> -		iommu_group_put(gr3d->group);
>>> -	}
>>> -
>>>  	return 0;
>>>  }
>>>  
>>>
>>
>> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
>>
>> Though I'd prefer to have tegra->group renamed, maybe to 'shared_dc_group'.
> 
> tegra->group doesn't bother me at all. I think just the fact that it's
> in struct tegra_drm implies that it is shared. It's also declared
> closely to all the other "shared" variables, so I think that makes it
> pretty clear. If there were other IOMMU groups I'd agree that renaming
> it would be good to clarify the purpose. But as it is, I think there's
> no need for that.
> 
> Thanks for the review!

Well, okay. On the other hand IOMMU API should handle re-attaching from a
different device and then that shared group isn't needed at all. Does that
re-attaching cause any problems right now? If yes, maybe it's worth fixing the
root of the problem rather than trying to workaround it.
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