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

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Date:   Fri, 4 May 2018 14:31:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...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 04.05.2018 13:54, Thierry Reding wrote:
> 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.

Sounds good.