Host1x Infrastructure Reference¶

structhost1x_client_ops¶

host1x client operations

Definition

struct host1x_client_ops {  int (*init)(struct host1x_client *client);  int (*exit)(struct host1x_client *client);  int (*suspend)(struct host1x_client *client);  int (*resume)(struct host1x_client *client);};

Members

init

host1x client initialization code

exit

host1x client tear down code

suspend

host1x client suspend code

resume

host1x client resume code

structhost1x_client¶

host1x client structure

Definition

struct host1x_client {  struct list_head list;  struct device *host;  struct device *dev;  struct iommu_group *group;  const struct host1x_client_ops *ops;  enum host1x_class class;  struct host1x_channel *channel;  struct host1x_syncpt **syncpts;  unsigned int num_syncpts;  struct host1x_client *parent;  unsigned int usecount;  struct mutex lock;};

Members

list

list node for the host1x client

host

pointer to struct device representing the host1x controller

dev

pointer to struct device backing this host1x client

group

IOMMU group that this client is a member of

ops

host1x client operations

class

host1x class represented by this client

channel

host1x channel associated with this client

syncpts

array of syncpoints requested for this client

num_syncpts

number of syncpoints requested for this client

parent

pointer to parent structure

usecount

reference count for this structure

lock

mutex for mutually exclusive concurrency

structhost1x_driver¶

host1x logical device driver

Definition

struct host1x_driver {  struct device_driver driver;  const struct of_device_id *subdevs;  struct list_head list;  int (*probe)(struct host1x_device *device);  int (*remove)(struct host1x_device *device);  void (*shutdown)(struct host1x_device *device);};

Members

driver

core driver

subdevs

table of OF device IDs matching subdevices for this driver

list

list node for the driver

probe

called when the host1x logical device is probed

remove

called when the host1x logical device is removed

shutdown

called when the host1x logical device is shut down

inthost1x_device_init(struct host1x_device * device)¶

initialize a host1x logical device

Parameters

structhost1x_device*device

host1x logical device

Description

The driver for the host1x logical device can call this during execution ofitshost1x_driver.probe implementation to initialize each of its clients.The client drivers access the subsystem specific driver data using thehost1x_client.parent field and driver data associated with it (usually bycalling dev_get_drvdata()).

inthost1x_device_exit(struct host1x_device * device)¶

uninitialize host1x logical device

Parameters

structhost1x_device*device

host1x logical device

Description

When the driver for a host1x logical device is unloaded, it can call thisfunction to tear down each of its clients. Typically this is done after asubsystem-specific data structure is removed and the functionality can nolonger be used.

inthost1x_driver_register_full(structhost1x_driver * driver, struct module * owner)¶

register a host1x driver

Parameters

structhost1x_driver*driver

host1x driver

structmodule*owner

owner module

Description

Drivers for host1x logical devices call this function to register a driverwith the infrastructure. Note that since these drive logical devices, theregistration of the driver actually triggers tho logical device creation.A logical device will be created for each host1x instance.

voidhost1x_driver_unregister(structhost1x_driver * driver)¶

unregister a host1x driver

Parameters

structhost1x_driver*driver

host1x driver

Description

Unbinds the driver from each of the host1x logical devices that it isbound to, effectively removing the subsystem devices that they represent.

inthost1x_client_register(structhost1x_client * client)¶

register a host1x client

Parameters

structhost1x_client*client

host1x client

Description

Registers a host1x client with each host1x controller instance. Note thateach client will only match their parent host1x controller and will only beassociated with that instance. Once all clients have been registered withtheir parent host1x controller, the infrastructure will set up the logicaldevice and callhost1x_device_init(), which will in turn call each client’shost1x_client_ops.init implementation.

inthost1x_client_unregister(structhost1x_client * client)¶

unregister a host1x client

Parameters

structhost1x_client*client

host1x client

Description

Removes a host1x client from its host1x controller instance. If a logicaldevice has already been initialized, it will be torn down.

Host1x Syncpoint Reference¶

u32host1x_syncpt_id(struct host1x_syncpt * sp)¶

retrieve syncpoint ID

Parameters

structhost1x_syncpt*sp

host1x syncpoint

Description

Given a pointer to a struct host1x_syncpt, retrieves its ID. This ID isoften used as a value to program into registers that control how hardwareblocks interact with syncpoints.

u32host1x_syncpt_incr_max(struct host1x_syncpt * sp, u32 incrs)¶

update the value sent to hardware

Parameters

structhost1x_syncpt*sp

host1x syncpoint

u32incrs

number of increments

inthost1x_syncpt_incr(struct host1x_syncpt * sp)¶

increment syncpoint value from CPU, updating cache

Parameters

structhost1x_syncpt*sp

host1x syncpoint

inthost1x_syncpt_wait(struct host1x_syncpt * sp, u32 thresh, long timeout, u32 * value)¶

wait for a syncpoint to reach a given value

Parameters

structhost1x_syncpt*sp

host1x syncpoint

u32thresh

threshold

longtimeout

maximum time to wait for the syncpoint to reach the given value

u32*value

return location for the syncpoint value

struct host1x_syncpt *host1x_syncpt_request(structhost1x_client * client, unsigned long flags)¶

request a syncpoint

Parameters

structhost1x_client*client

client requesting the syncpoint

unsignedlongflags

flags

Description

host1x client drivers can use this function to allocate a syncpoint forsubsequent use. A syncpoint returned by this function will be reserved foruse by the client exclusively. When no longer using a syncpoint, a host1xclient driver needs to release it usinghost1x_syncpt_free().

voidhost1x_syncpt_free(struct host1x_syncpt * sp)¶

free a requested syncpoint

Parameters

structhost1x_syncpt*sp

host1x syncpoint

Description

Release a syncpoint previously allocated usinghost1x_syncpt_request(). Ahost1x client driver should call this when the syncpoint is no longer inuse. Note that client drivers must ensure that the syncpoint doesn’t remainunder the control of hardware after calling this function, otherwise twoclients may end up trying to access the same syncpoint concurrently.

u32host1x_syncpt_read_max(struct host1x_syncpt * sp)¶

read maximum syncpoint value

Parameters

structhost1x_syncpt*sp

host1x syncpoint

Description

The maximum syncpoint value indicates how many operations there are inqueue, either in channel or in a software thread.

u32host1x_syncpt_read_min(struct host1x_syncpt * sp)¶

read minimum syncpoint value

Parameters

structhost1x_syncpt*sp

host1x syncpoint

Description

The minimum syncpoint value is a shadow of the current sync point value inhardware.

u32host1x_syncpt_read(struct host1x_syncpt * sp)¶

read the current syncpoint value

Parameters

structhost1x_syncpt*sp

host1x syncpoint

struct host1x_syncpt *host1x_syncpt_get(struct host1x * host, unsigned int id)¶

obtain a syncpoint by ID

Parameters

structhost1x*host

host1x controller

unsignedintid

syncpoint ID

struct host1x_syncpt_base *host1x_syncpt_get_base(struct host1x_syncpt * sp)¶

obtain the wait base associated with a syncpoint

Parameters

structhost1x_syncpt*sp

host1x syncpoint

u32host1x_syncpt_base_id(struct host1x_syncpt_base * base)¶

retrieve the ID of a syncpoint wait base

Parameters

structhost1x_syncpt_base*base

host1x syncpoint wait base

Display Controllers¶

Tegra SoCs have two display controllers, each of which can be associated withzero or more outputs. Outputs can also share a single display controller, butonly if they run with compatible display timings. Two display controllers canalso share a single framebuffer, allowing cloned configurations even if modeson two outputs don’t match. A display controller is modelled as a CRTC in KMSterms.

On Tegra186, the number of display controllers has been increased to three. Adisplay controller can no longer drive all of the outputs. While two of thesecontrollers can drive both DSI outputs and both SOR outputs, the third cannotdrive any DSI.

Outputs¶

The type and number of supported outputs varies between Tegra SoC generations.All generations support at least HDMI. While earlier generations supported thevery simple RGB interfaces (one per display controller), recent generations nolonger do and instead provide standard interfaces such as DSI and eDP/DP.

Outputs are modelled as a composite encoder/connector pair.

GEM Buffers¶

TheDRM_IOCTL_TEGRA_GEM_CREATE IOCTL is used to create a GEM buffer objectwith Tegra-specific flags. This is useful for buffers that should be tiled, orthat are to be scanned out upside down (useful for 3D content).

After a GEM buffer object has been created, its memory can be mapped by anapplication using the mmap offset returned by theDRM_IOCTL_TEGRA_GEM_MMAPIOCTL.

Syncpoints¶

The current value of a syncpoint can be obtained by executing theDRM_IOCTL_TEGRA_SYNCPT_READ IOCTL. Incrementing the syncpoint is achievedusing theDRM_IOCTL_TEGRA_SYNCPT_INCR IOCTL.

Userspace can also request blocking on a syncpoint. To do so, it needs toexecute theDRM_IOCTL_TEGRA_SYNCPT_WAIT IOCTL, specifying the value ofthe syncpoint to wait for. The kernel will release the application when thesyncpoint reaches that value or after a specified timeout.

Command Stream Submission¶

Before an application can submit command streams to host1x it needs to open achannel to an engine using theDRM_IOCTL_TEGRA_OPEN_CHANNEL IOCTL. ClientIDs are used to identify the target of the channel. When a channel is nolonger needed, it can be closed using theDRM_IOCTL_TEGRA_CLOSE_CHANNELIOCTL. To retrieve the syncpoint associated with a channel, an applicationcan use theDRM_IOCTL_TEGRA_GET_SYNCPT.

After opening a channel, submitting command streams is easy. The applicationwrites commands into the memory backing a GEM buffer object and passes theseto theDRM_IOCTL_TEGRA_SUBMIT IOCTL along with various other parameters,such as the syncpoints or relocations used in the job submission.