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android_kernel_samsung_msm8976/Documentation/arm/msm/tspp.txt
Gilad Broner c033e86e67 msm: tspp: Remove tspp driver user-space API 
tspp driver user-space API is not in fact used and
therefore was not maintained so it is obsolete.
With 64bit porting in mind it was decided this driver
will no longer be visible as char device to user.
The driver will be operated via the dvb/demux device
and user-space API.

Change-Id: Ib6a9240a211334bd968a3558bd1783a24aeacda7
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>
2014-03-12 09:22:23 +02:00

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Introduction
============
The TSPP (Transport stream packet processor) is a hardware accelerator
designed to process MPEG2 TS (transport stream) data. It is mainly used for
broadcast terrestrial services to off-load the host CPU from real-time
sensitive TS processing for high bandwidth streams (~20Mbps). Data is received
either via TSIF (Transport stream interface) or system memory.
The TSPP driver manages the TSIF 12Seg HW core, which consists of a TSPP, a
BAM (Bus access manager, used for DMA) and two TSIF inputs.
It is applicable to the TSIF 12Seg core found on select Qualcomm MSM chips.
For more information on the TSIF interface, please refer to TSIF documentation
(Documentation/arm/msm/tsif.txt).
For more information on the BAM interface, please refer to SPS documentation
(Documentation/dma/sps/sps_architecture.txt).
Hardware description
====================
The TSPP unit expands the capabilities of the TSIF interface by adding MPEG2
stream processing such as:
- Elementary Stream PID filtering and de-multiplexing
- Several TSP processing operation modes:
- TSP Raw processing (with or w/o suffix)
- TSP PES assembly
- Error handling
- Multi2 decryption
+-------------+ +------+
+>|ARM subsystem| |Memory|
| +-------------+ +------+
| | |
I| | |
R| ========================== System bus
Q| |
s| | TSIF 12Seg
| +-----------------------+
| | +---+ |
| | |BAM| |
| | +---+ | GPIOs
| | | +------+--|-------- TSIF 0 clk
| | +----+ |TSIF 0|--|-------- TSIF 0 data
+-| | |-----+------+--|-------- TSIF 0 en
| |TSPP| |
| | |-----+------+--|-------- TSIF 1 clk
| +----+ |TSIF 1|--|-------- TSIF 1 data
| +------+--|-------- TSIF 1 en
+-----------------------+
The TSPP unit receives an MPEG2 transport stream either via the two TSIF
interfaces, or via system memory.
It uses the BAM interface to transfer data to and from system memory.
The ARM subsystem receives interrupts on various error conditions from TSPP
and TSIF units, and on data transfer events from the BAM.
Software Description
====================
The TSPP driver is responsible for:
- TSPP/TSIF hardware configuration (using SPS driver to configure BAM
hardware)
- TSIF GPIO/Clocks configuration
- Memory resource management
- Handling TSIF/TSPP interrupts and BAM events
- TSPP Power management
TSPP Terminology
----------------
Device - the TSPP hardware instance
- the device contains many streams
Stream: All data that is received from a particular TS packet source
- For example, MPEG2 Transport Stream from TSIF0
- A stream can consist of many channels
Channel: A channel routes part of a stream to a specified memory location
- For example, video and audio can be routed to different memory locations
using different channels
- Channel contents are defined by filters
Filter: Enables TS packet filtering and routing according to PID (packet ID)
- The decision regarding which PIDs in the stream will be routed to a
channel is done via filters
- Several filters can be registered to the same channel
- Filters can pass TS packets as-is (Raw mode) or assemble them into PES
packets (PES mode)
- Groups of contiguous PIDs can be filtered together (i.e. PSI/SI 0x0-0x2F,
1Seg PMTs 0x1FC8-0x1FCF)
- Filters can be used to discard packets (e.g. eliminate processing of
unwanted channels)
Init flow:
----------
Driver registers BAM (via SPS driver) and initializes TSIF/TSPP hardware.
Control path:
-------------
1. Client opens a TSPP channel and stream
2. Client notifies the driver of the source stream (TSIF0/TSIF1/Memory)
- TSPP driver allocates memory for the channel (circular buffer)
- As the amount of memory varies according to stream bandwidth (which the
driver doesn't know), a client can hint to the driver about the required
memory or stream bandwidth
- TSPP driver configures TSIF/BAM hardware according to selected stream
3. Client notifies the driver to filter a set of PIDs for the selected channel
- TSPP driver configures TSPP hardware filters accordingly
4. Client can now read data received from the selected channel
Optional: Scrambling keys can be configured for a filter to decrypt Multi2
encrypted streams. The scrambling keys are received encrypted in-stream every
~2 seconds. The client uses a smart card and master key to decrypt the
received scrambling keys. The master key remains inside the smart card and is
never revealed to software.
Conceptual flow:
Client TSPP Driver SPS Driver Hardware
| | | |
| | Init TSIF/TSPP | |
| |---------------------------|------------------>|
| | Register BAM | |
| |-------------------------->| |
| | | |
| open_channel(ch_id) | | |
|-------------------------->| | |
| open_stream(ch_id, TSIF0) | | |
|-------------------------->| | |
| | buff[0..N] = alloc() | |
| |----------> | |
| | Connect(TSPP,MEM) | |
| |-------------------------->| |
| | Transfer(buff[0..N]) | |
| |-------------------------->| |
| | | |
| | Configure TSIF0 | |
| |---------------------------|------------------>|
| | | |
| tspp_add_filter(ch_id, f) | | |
|-------------------------->| | |
| | Configure TSPP filters | |
| |---------------------------|------------------>|
| | | |
| | | INT |
| | |<------------------|
| | notify(EOT,buff[x]) | |
| |<--------------------------| |
| | Transfer(buff[y]) | |
| |-------------------------->| |
| | | |
| read from buff[x] | | |
|-------------------------->| | |
| | | |
Data path:
----------
The TSPP driver is not involved in data transfer, other than managing the
circular buffer pointers when a transfer is complete. Data loss can occur if
a client cannot keep up with stream bandwidth.
The driver does not notify the client if there is data loss. It is
assumed that the client will read data when the data is ready, and when
the client is able.
API
===
Refer to msm_tspp.h for complete listing of the API functions and structures,
and to driver implementation under drivers/media/platform/msm/broadcast/tspp.c
Design
======
Design is based on the existing TSIF driver, with added control functionality
for the extra hardware features.
Power Management
===============
TSPP driver prevents MSM from sleeping while TSPP hardware is active.
To achieve this, the driver holds the wake lock. When no channels are
configured to receive data, the driver stops the clocks to save power.
It will register for suspend/resume in the future.
SMP/multi-core
==============
Driver is fully SMP aware.
Performance
===========
Control flows are rare.
Data path only involves maintaining the circular buffer pointers.
Interface
=========
Driver exposes function based interface for other kernel drivers.
Please see sequence under software description for more info.
Debugfs may be used for debug purposes. Through debugfs, all of the TSIF
registers can be accessed under /sys/kernel/debug/tsif0 and tsif1. The
TSPP registers are found under /sys/kernel/debug/tspp0. If you cannot
see these devices, then either the driver has been built without debugfs
support (check the define TSPP_USE_DEBUGFS in tspp.c) or the debugfs has
not been mounted correctly (or mounted in a different location).
Driver Parameters
=================
TSPP driver has target-specific parameters:
- Memory base addresses for TSIF/TSPP/BAM
- TSIF/TSPP/BAM IRQ numbers
- TSIF GPIO numbers
Config Options
==============
To enable the driver, set CONFIG_TSPP (=y or =m) in the appropriate
config file for the platform.
Dependencies
============
The TSPP driver depends on the SPS driver to configure BAM hardware.
Known Issues
============
Currently PES processing mode cannot be configured for streams in which the PES
length is 0. This is a HW limitation.
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