linux-kernel - Re: [PATCH v1 2/5] drm/tegra: gr2d: Add IOMMU support

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Date:   Fri, 4 May 2018 12:54:16 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/5] drm/tegra: gr2d: Add IOMMU support

On Fri, May 04, 2018 at 02:47:20AM +0300, Dmitry Osipenko wrote:
> Attach GR2D to the display IOMMU group in order to provide GR2D access
> to BO's IOVA.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/gpu/drm/tegra/gr2d.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tegra/gr2d.c b/drivers/gpu/drm/tegra/gr2d.c
> index 9a8ea93016a9..8eb530a85dd0 100644
> --- a/drivers/gpu/drm/tegra/gr2d.c
> +++ b/drivers/gpu/drm/tegra/gr2d.c
> @@ -7,12 +7,14 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/iommu.h>
>  
>  #include "drm.h"
>  #include "gem.h"
>  #include "gr2d.h"
>  
>  struct gr2d {
> +	struct iommu_group *group;
>  	struct tegra_drm_client client;
>  	struct host1x_channel *channel;
>  	struct clk *clk;
> @@ -30,7 +32,9 @@ 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;
>  
>  	gr2d->channel = host1x_channel_request(client->dev);
>  	if (!gr2d->channel)
> @@ -42,23 +46,46 @@ static int gr2d_init(struct host1x_client *client)
>  		return -ENOMEM;
>  	}
>  
> -	return tegra_drm_register_client(dev->dev_private, drm);
> +	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);
> +				host1x_syncpt_free(client->syncpts[0]);
> +				host1x_channel_put(gr2d->channel);
> +				iommu_group_put(gr2d->group);
> +				return err;
> +			}
> +		}
> +	}

This is almost identical to the code in DC, perhaps we should factor
this out into a separate helper? Nothing that needs to be done right
now, I'll take a look at it and see if I can come up with something
good in a follow-up patch.

> +
> +	return tegra_drm_register_client(tegra, drm);
>  }
>  
>  static int gr2d_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 gr2d *gr2d = to_gr2d(drm);
>  	int err;
>  
> -	err = tegra_drm_unregister_client(dev->dev_private, drm);
> +	err = tegra_drm_unregister_client(tegra, drm);
>  	if (err < 0)
>  		return err;
>  
>  	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;
>  }
>  

Thierry

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