197 lines
7.6 KiB
Plaintext
197 lines
7.6 KiB
Plaintext
|
Introduction
|
||
|
|
============
|
||
|
|
|
||
|
|
Glink packet drivers are companion adaptation driver which use the kernel APIs
|
||
|
|
to expose the Glink core logical channels as charecter devices to the
|
||
|
|
user-space clients.
|
||
|
|
|
||
|
|
The Glink core APIs are detailed in Documentation/arm/msm/glink.txt.
|
||
|
|
|
||
|
|
Software description
|
||
|
|
====================
|
||
|
|
|
||
|
|
Glink packet drivers supports the Glink core APIs to user-space client through
|
||
|
|
standard file operations like open, read, write, ioctl, poll and release etc.
|
||
|
|
The standard Linux permissions are used for the device node and SELinux does
|
||
|
|
further security checks.
|
||
|
|
|
||
|
|
|
||
|
|
Device node [0..n]
|
||
|
|
|
|
||
|
|
|
|
||
|
|
-------------------
|
||
|
|
| VFS Framework |
|
||
|
|
-------------------
|
||
|
|
| |
|
||
|
|
| |
|
||
|
|
------- -------
|
||
|
|
| CDEV | | CDEV |
|
||
|
|
| Dev 0 |...| Dev n |
|
||
|
|
----------------------
|
||
|
|
| Glink packet driver |
|
||
|
|
----------------------
|
||
|
|
|
|
||
|
|
|
|
||
|
|
-----------------
|
||
|
|
| |
|
||
|
|
| G-Link core |
|
||
|
|
| |
|
||
|
|
-----------------
|
||
|
|
|
|
||
|
|
|
|
||
|
|
To Remote System
|
||
|
|
|
||
|
|
|
||
|
|
The file operations map to the G-link client API as follows:
|
||
|
|
|
||
|
|
Open():
|
||
|
|
----------
|
||
|
|
The Open system call is mapped to glink_open() which opens a channel. The
|
||
|
|
expected channel configuration has to done through DT files. The full DT schema
|
||
|
|
is detailed in Documentation/devicetree/bindings/arm/msm/glinkpkt.txt.
|
||
|
|
|
||
|
|
Open on the glink packet character device is a blocking call which blocks until
|
||
|
|
the channel is fully open by both local processor and remote processor.
|
||
|
|
Clients can configure the blocking time through a device configurable parameter
|
||
|
|
defined per device.
|
||
|
|
|
||
|
|
The timeout value is specified in seconds with a default timeout of 1 second.
|
||
|
|
A negative value indicates an infinite wait.
|
||
|
|
|
||
|
|
Example:
|
||
|
|
# get open timeout value
|
||
|
|
cat /sys/class/glinkpkt/device_name/open_timeout
|
||
|
|
# set to 20 seconds value
|
||
|
|
echo 20 > /sys/class/glinkpkt/device_name/open_timeout
|
||
|
|
|
||
|
|
If the channel is not opened by remote processor or any other problem which
|
||
|
|
fails the channel to be ready will result in timeout and -ETIMEOUT will return
|
||
|
|
to client. Open on success returns the valid file descriptor to client and on
|
||
|
|
fail case standard Linux error codes.
|
||
|
|
|
||
|
|
The same device can be opened by multiple clients but passing the same file
|
||
|
|
descriptor from multiple threads may lead unexpected results.
|
||
|
|
|
||
|
|
Write():
|
||
|
|
----------
|
||
|
|
The Write system call is mapped to glink_tx() which transmits the data over the
|
||
|
|
glink channel.
|
||
|
|
|
||
|
|
Read():
|
||
|
|
----------
|
||
|
|
The Read system call consumes any pending data on the channel. Glink signals
|
||
|
|
incoming data through the glink_notify_rx() call back and the glink packet
|
||
|
|
driver queues the data internally and provides to client through read system
|
||
|
|
call. Once the Read is completed, the glink packet driver calls glink_rx_done()
|
||
|
|
API to notify the completion of receiving operation to Glink core.
|
||
|
|
|
||
|
|
+
|
||
|
|
User-Space | Kernel-Space
|
||
|
|
|
|
||
|
|
|
|
||
|
|
+---------+ | +----------+ +------------+
|
||
|
|
| Local | | | GlinkPKT | | |
|
||
|
|
| Client | | | Driver | | Glink core |
|
||
|
|
| | | | | | |
|
||
|
|
+---------+ | +----------+ +------------+
|
||
|
|
|
|
||
|
|
+ | + +
|
||
|
|
| | | |
|
||
|
|
| open() | glink_pkt_open() | glink_open() |
|
||
|
|
| +--------------> | +-----------------> | +-----------------> |
|
||
|
|
| | | |
|
||
|
|
| File Handle[fd]| Valid Fd | Handle |
|
||
|
|
| <--------------+ | <-----------------+ | <-----------------+ |
|
||
|
|
| | | |
|
||
|
|
| Ioctl() | | |
|
||
|
|
| QUEUE_RX_INTENT | glink_pkt_ioctl() | glink_queue_rx_intent()
|
||
|
|
| +--------------> | +-----------------> | +-----------------> |
|
||
|
|
| | | |
|
||
|
|
| | | |
|
||
|
|
| <----------------------------------------------------------+ |
|
||
|
|
| | | |
|
||
|
|
| Read() | glink_pkt_read() | |
|
||
|
|
| +--------------> | +-----------------> | +---+ |
|
||
|
|
| | | | |
|
||
|
|
| | Wait for data |
|
||
|
|
| | | <---+ |
|
||
|
|
| | | glink_notify_rx() |
|
||
|
|
| | | <-----------------+ |
|
||
|
|
| | Wake-up read() | |
|
||
|
|
| | copy_to_user() | |
|
||
|
|
| read() return | <-----------------+ | |
|
||
|
|
| <--------------+ | | |
|
||
|
|
+ | + +
|
||
|
|
|
|
||
|
|
|
|
||
|
|
+
|
||
|
|
|
||
|
|
Clients can also poll on device node for POLLIN mask to get notification for
|
||
|
|
any incoming data. Clients have to call the GLINK_PKT_IOCTL_QUEUE_RX_INTENT
|
||
|
|
ioctl to queue the RX buffer to glink core in advance.
|
||
|
|
|
||
|
|
Release():
|
||
|
|
----------
|
||
|
|
The Release system call is mapped to glink_close() to close a channel and free
|
||
|
|
the resources.
|
||
|
|
|
||
|
|
Poll():
|
||
|
|
----------
|
||
|
|
The Poll system call provides waiting operation like wait for incoming data on
|
||
|
|
POLLIN mask and to get the TIOCM signal notification on POLLPRI mask. Clients
|
||
|
|
can wait on poll for POLLPRI mask to get any notification regarding TICOM
|
||
|
|
signals. In SSR case Poll call will return with POLLHUP mask and in this case
|
||
|
|
client has to close and re-open the port.
|
||
|
|
|
||
|
|
* POLLPRI - TIOCM bits changed
|
||
|
|
* POLLIN - RX data available
|
||
|
|
* POLLHUP - link is down due to either remote side closing or an SSR
|
||
|
|
|
||
|
|
Ioctl():
|
||
|
|
----------
|
||
|
|
Multiple ioctls are supported to get the TICOM signal status and to queue the
|
||
|
|
Rx intent with Glink core. Supported ioctls are TIOCMSET, TIOCMGET, TIOCMBIS,
|
||
|
|
TIOCMBIC and GLINK_PKT_IOCTL_QUEUE_RX_INTENT.
|
||
|
|
|
||
|
|
The GLINK_PKT_IOCTL_QUEUE_RX_INTENT ioctl is mapped to glink_queue_rx_intent()
|
||
|
|
API which queues an RX intent with Glink core.
|
||
|
|
|
||
|
|
Signals:
|
||
|
|
==========
|
||
|
|
Glink protocol provoide 32-bit control signal field to pass through for the
|
||
|
|
clients-specific signaling where as Glink packet driver client which are from
|
||
|
|
user space can use the signal filed as mentioned below.
|
||
|
|
|
||
|
|
* 31:28 - Reserved for SMD RS-232 signals
|
||
|
|
* 27:16 - Pass through for client usage
|
||
|
|
* 15:0 - TICOM bits
|
||
|
|
|
||
|
|
SSR operation:
|
||
|
|
==============
|
||
|
|
On remote subsystem restart all open channels on that edge will be closed and
|
||
|
|
local clients have to close and re-open the channel to re-start the
|
||
|
|
communication. All blocking calls such as open, read and write will be returned
|
||
|
|
with -ENETRESET and the poll call will be return with the POLLHUP error codes.
|
||
|
|
|
||
|
|
Files:
|
||
|
|
==========
|
||
|
|
Documentation/devicetree/bindings/arm/msm/glinkpkt.txt
|
||
|
|
drivers/soc/qcom/msm_glink_pkt.c
|
||
|
|
|
||
|
|
Wakelock:
|
||
|
|
==========
|
||
|
|
By default, GLINK PKT will acquire a wakelock for 2 seconds. To optimize this
|
||
|
|
behavior, use the poll() function:
|
||
|
|
1. Client calls poll() which blocks until data is available to read
|
||
|
|
2. Data comes in, GLINK PKT grabs a wakelock and poll()is unblocked
|
||
|
|
3. Client grabs wakelock to prevent system from suspending
|
||
|
|
4. Client calls GLINK PKT read() to read the data
|
||
|
|
5. GLINK PKT releases its wakelock
|
||
|
|
6. Client Processes the data
|
||
|
|
7. Client releases the wakelock
|
||
|
|
|
||
|
|
Logging:
|
||
|
|
==========
|
||
|
|
cat /d/ipc_logging/glink_pkt/log_cont
|
||
|
|
|