AM335x-PSP 04.06.00.06 Features and Performance Guide

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= Read This First = '''  Content is no longer maintained and is being kept for reference only! '''

All performance numbers provided in this document are gathered using AM335x BeagleBone and Evaluation Module (version 1.1A) Board with ARM running at 720MHz and DDR2 configured at 266MHz clock.

About This Manual
This document provides a feature overview and performance data for each of the device drivers which are part of the Linux PSP package supporting AM335x BeagleBone and Evaluation Module (version 1.0D and above) boards. This document should be used in conjunction with release notes provided with the PSP package for information on specific issues present with drivers included in a particular release.

If You Need Assistance
For further information or to report any problems, contact http://community.ti.com/ or http://support.ti.com/

= Support Overview =

Boot Modes Supported
Green colored box in the table below means that the particular boot mode is supported on the device in the release.

NOTE These are supported boot modes in PSP software, the actual hardware may support many more boot modes than shown here. Please refer to hardware documentation for list of all supported boot modes.

U-Boot Support
U-Boot is the defacto bootloader for Linux kernel on ARM. The following features of U-Boot are supported in this release.

= Linux Kernel =

Kernel Virtual Memory Layout
The default AM335x kernel configuration, with "mem=128M" passed as boot argument, uses following Virtual Memory laout:  [    0.000000] Memory: 128MB = 128MB total [   0.000000] Memory: 124068k/124068k available, 7004k reserved, 0K highmem [   0.000000] Virtual kernel memory layout: [   0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB) [   0.000000]     fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB) [   0.000000]     DMA     : 0xffa00000 - 0xffe00000   (   4 MB) [   0.000000]     vmalloc : 0xc8800000 - 0xf8000000   ( 760 MB) [   0.000000]     lowmem  : 0xc0000000 - 0xc8000000   ( 128 MB) [   0.000000]     modules : 0xbf000000 - 0xc0000000   (  16 MB) [   0.000000]       .text : 0xc0008000 - 0xc0509000   (5124 kB) [   0.000000]       .init : 0xc0509000 - 0xc053e000   ( 212 kB) [   0.000000]       .data : 0xc053e000 - 0xc05887a0   ( 298 kB) [   0.000000]        .bss : 0xc05887c4 - 0xc05b4780   ( 176 kB)

= PSP Linux Drivers =

This section provides brief overview of the device drivers supported in the Linux PSP release.

Note: The constraints may vary across product releases. Please refer to the Release Notes accompanying the release for an updated list of constraints.

Device Driver List
The following table list the various device drivers supported and the device they are supported on. On detailed information on specific features or limitations of a pariticular driver, refer to the chapter catering to that driver in this document.

ALSA SoC Audio Driver
This section an overview of the ALSA SoC audio driver features along with the throughput and CPU load numbers.

Introduction
AM335x Audio driver complies to the Advanced Linux Sound Architecture (ALSA) System on Chip (SoC) framework (ASoC).

The ASoC framework splits an embedded audio system into three components:


 * Codec driver: The codec driver is generic and hardware independent code that configures the audio codec to provide audio capture and playback. It should contain no code that is specific to the target platform or machine.
 * Platform driver: The platform driver can be divided into audio DMA and SoC Digital Audio Interface (DAI) configuration and control. The platform driver only targets the SoC CPU and must have no board specific code.
 * Machine driver: The ASoC machine (or board) driver is the code that glues together the platform and codec drivers. It can contain codec and platform specific code. It registers the audio subsystem with the kernel as a platform device.

Following architecture diagram shows all the components and the interactions among them.

Driver Features
The driver supports the following features:


 * 1) Supports AIC3106 audio codec in ALSA SoC framework.
 * 2) Multiple sample rate support (8 KHz, 44.1 KHz and 48 KHz commonly used) for both capture and playback.
 * 3) Supports audio in stereo mode
 * 4) Supports simultaneous playback and record (full-duplex mode).
 * 5) Supports mixer interface for the audio codec

Features Not Supported

 * 1) OSS based applications, which use ALSA-OSS emulation layer, are not supported.
 * 2) Formats such as TDM, Left and Right Justified are currently not supported.
 * 3) Synthesizer and midi interfaces are not supported.

Constraints

 * 1) By default, codec is configured in master mode and McASP is used as slave. Testing of the audio sub-system is done in this configuration only.
 * 2) Sampling frequencies for playback and capture streams should be same.
 * 3) The audio driver does not allow opening the same stream (playback/capture) multiple times.

Supported System Calls
Refer ALSA project - the C library reference for API calls.

Performance and Benchmarks

 * 1) Access type - RW_INTERLEAVED
 * 2) Channels - 2
 * 3) Format - S16_LE
 * 4) Period size - 64

Ethernet Driver
This section provides an overview of the Ethernet driver features along with throughput and CPU load numbers. Ethernet driver follows standard Linux network interface architecture.

Introduction
The Ethernet driver supports the Linux netdev interface.

Driver Features
The driver supports the following features:


 * 1) 10/100/1000 Mbps mode of operation.
 * 2) Auto negotiation.
 * 3) Full duplex and half duplex mode of operation.
 * 4) Linux NAPI support
 * 5) Support for MII and RGMII interfaces to PHY
 * 6) CPSW Interrupt Pacing. This driver uses Timer 5 &amp; 6 for CPSW Interrupt Pacing. Re-using this timer for any other purpose will result in CPSW Interrupt Pacing not working correctly.

Features Not Supported

 * 1) Promiscuous mode of operation.
 * 2) Second switch port.
 * 3) IEEE 1588
 * 4) VLAN (Subscription common for all ports)
 * 5) Ethertool (Supports only Slave 0)
 * 6) Switch mode of operation

Supported System Calls
Supports the socket and related system calls in accordance with Linux architecture.

Performance and Benchmarks
The performance numbers were captured using the iperf tool. Usage details are mentioned below:


 * iperf version 2.0.4
 * On PC Host invoke iperf in the server mode : # iperf -s 
 * On the DUT iperf is invoked in client mode : # iperf -c &lt;server ip&gt; -w &lt;window size&gt; -m -f M -d -t 60 . This starts bi-directional traffic to the server for a duration of 60 seconds
 * Interrupt pacing feature enabled with pacing interval set to 500usecs ( # ethtool -C eth0 rx-usecs 500 )
 * The transfers are measured over a duration of 60Secs
 * Cross cable is used to measure performance.
 * Speed is set to 1000Mbps

Graphical LCD (GLCD) Driver
This chapter describes the GLCD driver architecture, driver features and performance numbers (throughput and CPU load).

Introduction
GLCD driver is based on Fbdev framework and it reuses da8xx-fb used on AM18x device. The LCDC IP on AM335x is an upgraded version of that found on AM18x SoC.

Driver Features
The driver supports the following features:


 * 1) Supports WVGA display through Fbdev framework.
 * 2) Supports display of ARGB:8888 images at max resolution 2048*2048, but pixel clock can be driven Max 150MHz.
 * 3) Supports getting and setting the variable screen information.
 * 4) Supports retrieving the fixed screen information.

Features Not Supported

 * 1) Brightness and color control ioctls not supported.

Constraints

 * 1) There is limit on Max pixel clock of 150MHz.

Supported System Calls
open, close, read, mmap, ioctl

Performance Benchmarks
Performance and Benchmarks not available in this release.

NAND Driver
This section provides an overview of the NAND flash driver features along with throughput and CPU load numbers.

Introduction
The NAND driver is implemented as a character and block driver, compliant with the Linux MTD subsystem interface. It supports various NAND Flash chips (see file  in Linux kernel sources). The NAND driver creates the device nodes for user space access (, ,  ,   and so on.).

This figure illustrates the stack diagram of NAND flash driver in Linux.

Driver Features
The driver supports the following features:


 * 1) BCH8 with Hardware Error Correction is supported
 * 2) Supports Read, Write and Erase
 * 3) Bad Block Management
 * 4) Polled Prefetch mode of transfer (enabled by default)
 * 5) SLC NAND

Features Not Supported

 * 1) DMA Mode of operation

Supported System Calls
Supports the system call support proivided by Linux MTD interface viz. open, close, read, write, ioctl

Performance Benchmarks
Please refer MTD Test Setup before proceeding.

SPI Flash Driver
This chapter describes the SPI flash driver architecture, driver features and performance numbers (throughput and CPU load).

Introduction
SPI Flash driver is implemented as block driver and compliant with standard MTD driver. It supports various flash devices. The SPI flash driver creates device node for user space access (example, /dev/mtd1).

Driver Features
The driver supports the following features:


 * 1) PIO and DMA Mode of Operation are supported.

Supported System Calls
Supports the system call support proivided by MTD interface viz. open, close, read, write, ioctl

Performance Benchmarks
Test setup is available here.

 NOTE  Over all SPI performance is low because we can only do a 24MHz clock on the board against the theoretical max of 48 MHz. Also high CPU load on write is expected because the SPI flash driver does a write every page size (256 bytes) resulting in high interrupt load.

MMC/SD Driver
This chapter provides details on MMC/SD driver along with throughput and CPU load numbers.

Introduction
The MMC controller provides an interface to external MMC cards that follow the MMC specification v4.0. The MMC driver is implemented as a block driver. Block device nodes(such as /dev/mmcblockp1, /dev/mmcblockp2) are created for user space access.

Driver Features
The driver supports the following features:


 * 1) MMC/SD native protocol command/response set
 * 2) Single/multiple block data transfers
 * 3) Linux file system and generic MMC layer abstract details of block devices (MMC)
 * 4) High-speed (SDv1.1) and High Capacity (SDv2.0) cards
 * 5) Support for 4 bit modes
 * 6) Support for card detect and Write protect features
 * 7) DMA and polled mode for data transfer operations

Features Not Supported

 * 1) Support for 1-bit, 8-bit mode of operation.
 * 2) SPI mode of operation
 * 3) PIO mode of operation

Constraints

 * 1) MMC/SD cards should not be removed when the mount operation is in progress. If done so, data integrity cannot be guaranteed.

Supported System Calls
open,close,read,write

Performance and Benchmarks
IMPORTANT The performance numbers can be severely affected if the media is mounted in sync mode. Hot plug scripts in the filesystem mount removable media in sync mode to ensure data integrity. For performance sensitive applications, umount the auto-mounted filesystem and re-mount in async mode. Please refer MMC/SD Test Setup before proceeding.

EXT2 file system
The performance numbers were captured using the following:


 * SD Card (Sandisk, MicroSDHC, Class 4, 8GB)
 * File System: ext2
 * Partition was mounted with async option

VFAT file system
The performance numbers were captured using the following:


 * SD Card (Sandisk, MicroSDHC, Class 4, 8GB)
 * File System: vfat
 * Partition was mounted with async option

UART Driver
This chapter provides details on UART driver.

Introduction
The UART driver is implemented as a serial driver, and can be accessed from user space as /dev/ttyOX(X=0-5)

Features Not Supported

 * Hardware Flow Control

Supported System Calls
open,close,read,write,ioctl

Performance and Benchmarks
Performance and Benchmarks not available in this release.

I2C Driver
This chapter provides details on I2C driver.

Introduction
The I2C peripheral is compliant with the Philips Semiconductor I2C-bus specification version 2.1. The I2C driver is implemented as a serial driver. The I2C driver can be accessed from the user space as /dev/i2c/0.

Driver Features
The driver supports the following features:


 * 1) 7-bit addressing mode
 * 2) Fast mode
 * 3) Interrupt mode

Features Not Supported

 * 1) 7-bit and 10-bit addressing combined format is not supported
 * 2) DMA mode is not supported

Supported System Calls
open,close,read,write,ioctl

Performance and Benchmarks
Performance and Benchmarks not available in this release.

EDMA Driver
This chapter provides details on EDMA driver along with throughput and CPU load numbers.

Introduction
The EDMA controller handles all data transfers between the level-two (L2) cache/memory controller and the device peripherals. On AM335x EDMA has has one instance of Channel controller. Each EDMA instance supports up to 32-dma channels and 8 QDMA channels. The EDMA consists of a scalable Parameter RAM (PaRAM) that supports flexible ping-pong, circular buffering, channel-chaining, auto-reloading, and memory protection. The EDMA allows movement of data to/from any addressable memory spaces, including internal memory (L2 SRAM), peripherals, and external memory.

The EDMA driver exposes only the kernel level API's. This driver is used as a utility by other drivers for data transfer.

Driver Features
The driver supports the following features:


 * 1) Request and Free DMA channel
 * 2) Programs DMA channel
 * 3) Start and Synchronize with DMA transfers
 * 4) Provides DMA transaction completion callback to applications
 * 5) Multiple instances of EDMA driver on a single processor

Features Not Supported

 * 1) QDMA is not supported.
 * 2) Reservation of resources (channels and PaRAMs) for usage from other masters is not supported.

Introduction
Touchscreen controller on AM335x is an 8 channel general purpose ADC, with optional support for interleaving Touch Screen conversions for a 4-wire, 5-wire, or 8-wire resistive panel. A resistive touchscreen operates by applying a volatge across a resistive network and measuring the change in resistance at a given point on the matrix where the screen is touched by an input (stylus or finger). The change in the resistance ratio marks the location on the touchscreen.

Driver Features
The driver supports the following features:


 * Resistive touchscreen
 * Hardware synchronized one shot mode
 * Programmable Open delay/Sampling delay before sampling each channel
 * Programmable averaging of input samples - 16
 * Support for servicing FIFOs via CPU.
 * ADC sampled data is 12-bit wide.
 * Pressure(z) measurements.

Features Not Supported

 * DMA Request event.

Watchdog(WDT) Driver
This chapter provides details on Watchdog timer driver.

Introduction
AM335x has a 32-bit watchdog timer which can be used to reset the hardware in case of a software fault. Once the /dev/watchdog is opened, it will reboot the system unless a user space daemon resets the timer at regular intervals within a certain timeout period. If watchdog device node is closed before timeout also reboot won't happen. The WDT driver is registered as a misc device. Default timeout of this driver is 60 seconds.

Driver Features
The driver supports the following features:


 * 1) Supports IOCTLs to set/get the timeout value, ping the watchdog &amp; query the watchdog structure info.
 * 2) Driver can be built as a loadable module and inserted dynamically.

Supported System Calls
open, close, write, ioctl, read

USB Driver
This chapter provides details on MUSB drivers along with throughput and CPU load numbers.

This chapter describes the MUSB driver architecture, features supported/not supported, constraints and performance numbers.

Description
The MUSB driver is implemented on top of Mentor OTG IP version 2.0 which supports all the speeds (High, Full and Low (host mode only)). On AM335x, MUSB uses CPPI 4.1 DMA for all the transfers.

Driver Features
The driver supports the following features:

Host Mode


 * 1) Human Interface Class (HID)
 * 2) Mass Storage Class (MSC)
 * 3) Hub Class

Gadget mode


 * 1) Mass Storage Class (MSC)
 * 2) USB Networking - RNDIS/CDC

Features Not Supported

 * 1) OTG
 * 2) USB Host Video Class (UVC)
 * 3) USB Host Audio Class (UAC)
 * 4) USB CDC HOST (USBNET)

Driver Features
The driver supports the following features:


 * 1) DMA mode
 * 2) PIO mode

Supported System Calls
open, close, read, write, ioctl

Performance Benchmarks
IMPORTANT For Mass-storage applications, the performance numbers can be severely affected if the media is mounted in sync mode. Hot plug scripts in the filesystem mount removable media in sync mode to ensure data integrity. For performance sensitive applications, umount the auto-mounted filesystem and re-mount in async mode.

Setup : WesternDigital HDD (500GB) is connected to usb0 port. File read/write performance data on usb0 port (WDD HDD) is captured. For detailed test setup refer to USB MSC host test setup

Description
This figure illustrates the stack diagram of the system with USB File Storage Gadget driver

Driver Features
The driver supports the following features:


 * 1) DMA mode
 * 2) PIO mode
 * 3) File backed storage driver was tested with SD media as the storage medium

Performance Benchmarks
The performance numbers are captured in DMA/PIO Mode using a file inside /dev/shm as storage gadget media exposing as removable media to Windows-XP over USB. The storage media is formatted using the NTFS on Windows-XP. Storage gadget media file is created using the command:


 * 1) dd if=/dev/zero of=/dev/shm/50M bs=1M count=50"

Insert the USB mass storage gadget with  as the backing storage:


 * 1) insmod g_mass_storage.ko file=/dev/shm/50M

For test setup details refer to msc-device setup

Description
The CDC RNDIS gadget driver that is used to send standard Ethernet frames using USB. The driver will create an Ethernet device by the name usb0.

Driver Features
The driver supports the following features:


 * 1) DMA mode
 * 2) PIO mode
 * 3) 10/100 Mbps speed.

Supported System Calls
open, close, read, write, ioctl</tt>

Performance Benchmarks
Performance benchmarks were collected using the Iperf tool and default options were used to collect the throughput numbers.

Description
The event sub system creates /dev/input/event* devices with the help of mdev.

Driver Features
The driver supports the following features:


 * 1) DMA mode
 * 2) PIO mode
 * 3) USB Mouse and Keyboards that conform to the USB HID specifications

DCAN Driver
This section provides details on DCAN driver.

Introduction
The CAN (DCAN) driver supports the Linux netdev interface. CAN driver supports transmitting and receiving in-order packets, processing happens at various bit rates.

Driver Features
The driver supports the following features:


 * 1) SocketCAN networking framework
 * 2) Linux NAPI support for Rx operations
 * 3) Local loopback of sent frames (IFF_ECHO)
 * 4) Standard CAN bus bit-rates namely 10K, 20K, 50K, 100K, 125K, 250K, 500K &amp; 1M

Features Not Supported

 * 1) ID filtering / Acceptance masks - since Linux infrastructure does not support this the driver cannot provide the feature

Supported System Calls
Supports the  and related system calls in accordance with Linux architecture. Refer to  under   folder

Introduction
AM335x devices provides a rich set of power management features. The features include clock control at module level, multiple power and voltage domains etc.

This section provides an overview of power management features supported and steps to enable these features in the kernel configuration. It also provides the typical power consumption measurement observed for different scenarios.

cpuidle
When idle loop is executed, kernel is not doing any useful 'work'. This is an opportunity to save power. The  framework helps in saving power during the idle state.

cpufreq
CPU is not loaded evenly during execution. This provides an opportunity to save power by adjusting/scaling voltage and frequency based on the current cpu load.

Power Measurements
The measurements in this section were done on AM335x EVM.

At each OPP
This section indicates the voltages measured for VDD_MPU and VDD_CORE at various OPPs (selected via ). The measurements were done with the  created using.