AM335x-PSP 04.06.00.10 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= Read This First = '''  Content is no longer maintained and is being kept for reference only!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 Evaluation Module with ARM running at 720MHz and DDR2 configured at 266MHz unless otherwise specified.

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. 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.

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=256M" passed as boot argument, uses following Virtual Memory laout: [   0.000000] Memory: 256MB = 256MB total [   0.000000] Memory: 253436k/253436k available, 8708k 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]     vmalloc : 0xd0800000 - 0xff000000   ( 744 MB) [   0.000000]     lowmem  : 0xc0000000 - 0xd0000000   ( 256 MB) [   0.000000]     modules : 0xbf000000 - 0xc0000000   (  16 MB) [   0.000000]       .text : 0xc0008000 - 0xc057c000   (5584 kB) [   0.000000]       .init : 0xc057c000 - 0xc05b9000   ( 244 kB) [   0.000000]       .data : 0xc05ba000 - 0xc0617fc0   ( 376 kB) [   0.000000]        .bss : 0xc0617fe4 - 0xc0644d64   ( 180 kB)

Interrupt Latency Measurement
The following table gives interrupt latency measurements taken across 1001 measurement samples.

Boot-time Measurement
Boot-time measurement was done with kernel built using. U-Boot environment variable bootargs is set to. U-Boot  variable is set to 0. Time from reset to "Login:" prompt was measured to be 16.063s.

Complete boot log with timestamps follows:

[Tue Jul 31 11:35:39.422 2012] [Tue Jul 31 11:35:39.422 2012] U-Boot SPL 2011.09 (Jul 20 2012 - 14:58:05) [Tue Jul 31 11:35:39.422 2012] Texas Instruments Revision detection unimplemented [Tue Jul 31 11:35:39.907 2012] Found a daughter card connected [Tue Jul 31 11:35:40.610 2012] [Tue Jul 31 11:35:40.610 2012] [Tue Jul 31 11:35:40.610 2012] U-Boot 2011.09 (Jul 20 2012 - 14:30:09) [Tue Jul 31 11:35:40.610 2012] [Tue Jul 31 11:35:40.610 2012] I2C:  ready [Tue Jul 31 11:35:40.657 2012] DRAM: 256 MiB [Tue Jul 31 11:35:40.907 2012] WARNING: Caches not enabled [Tue Jul 31 11:35:41.016 2012] Found a daughter card connected [Tue Jul 31 11:35:41.094 2012] NAND: HW ECC Hamming Code selected [Tue Jul 31 11:35:41.094 2012] 256 MiB [Tue Jul 31 11:35:41.094 2012] MMC:  OMAP SD/MMC: 0, OMAP SD/MMC: 1 [Tue Jul 31 11:35:41.579 2012] Net:  cpsw [Tue Jul 31 11:35:41.594 2012] Hit any key to stop autoboot: 0 [Tue Jul 31 11:35:41.735 2012] SD/MMC found on device 0 [Tue Jul 31 11:35:41.735 2012] reading uEnv.txt [Tue Jul 31 11:35:41.751 2012] [Tue Jul 31 11:35:41.751 2012] ** Unable to read "uEnv.txt" from mmc 0:1 ** [Tue Jul 31 11:35:41.751 2012] reading uImage [Tue Jul 31 11:35:42.110 2012] [Tue Jul 31 11:35:42.110 2012] 3163680 bytes read [Tue Jul 31 11:35:42.126 2012] ## Booting kernel from Legacy Image at 80007fc0 ... [Tue Jul 31 11:35:42.126 2012]   Image Name:   Arago/3.2.0-psp04.06.00.08.sdk/a [Tue Jul 31 11:35:42.172 2012]   Image Type:   ARM Linux Kernel Image (uncompressed) [Tue Jul 31 11:35:42.188 2012]   Data Size:    3163616 Bytes = 3 MiB [Tue Jul 31 11:35:42.188 2012]   Load Address: 80008000 [Tue Jul 31 11:35:42.188 2012]   Entry Point:  80008000 [Tue Jul 31 11:35:42.188 2012]   Verifying Checksum ... OK [Tue Jul 31 11:35:43.063 2012]   XIP Kernel Image ... OK [Tue Jul 31 11:35:43.079 2012] OK [Tue Jul 31 11:35:43.079 2012] [Tue Jul 31 11:35:43.079 2012] Starting kernel ... [Tue Jul 31 11:35:43.094 2012] [Tue Jul 31 11:35:43.094 2012] Uncompressing Linux... done, booting the kernel. [Tue Jul 31 11:35:44.032 2012] [   0.337524] mtdoops: mtd device (mtddev=name/number) must be supplied [Tue Jul 31 11:35:44.235 2012] [   0.541198] smartreflex smartreflex: am33xx_sr_probe: Zero NValue read from EFUSE [Tue Jul 31 11:35:44.266 2012] [   0.549591] sr_init: platform driver register failed [Tue Jul 31 11:35:45.344 2012] INIT: version 2.86 booting [Tue Jul 31 11:35:45.563 2012] Please wait: booting... [Tue Jul 31 11:35:45.641 2012] Starting udev [Tue Jul 31 11:35:46.891 2012] Remounting root file system... [Tue Jul 31 11:35:47.079 2012] Caching udev devnodes [Tue Jul 31 11:35:47.407 2012] ALSA: Restoring mixer settings... [Tue Jul 31 11:35:47.501 2012] No state is present for card EVM [Tue Jul 31 11:35:47.516 2012] Found hardware: "AM335X_EVM" "" "" "" "" [Tue Jul 31 11:35:47.516 2012] Hardware is initialized using a generic method [Tue Jul 31 11:35:47.516 2012] No state is present for card EVM [Tue Jul 31 11:35:47.532 2012] Configuring network interfaces... udhcpc (v1.13.2) started [Tue Jul 31 11:35:47.657 2012] Sending discover... [Tue Jul 31 11:35:50.657 2012] Sending discover... [Tue Jul 31 11:35:53.657 2012] Sending discover... [Tue Jul 31 11:35:53.673 2012] Sending select for 158.218.103.110... [Tue Jul 31 11:35:53.688 2012] Lease of 158.218.103.110 obtained, lease time 28800 [Tue Jul 31 11:35:53.704 2012] adding dns 158.218.108.21 [Tue Jul 31 11:35:53.907 2012] adding dns 157.170.32.67 [Tue Jul 31 11:35:53.907 2012] done. [Tue Jul 31 11:35:53.907 2012] Setting up IP spoofing protection: rp_filter. [Tue Jul 31 11:35:53.907 2012] Tue Jun 26 22:09:00 UTC 2012 [Tue Jul 31 11:35:53.907 2012] INIT: Entering runlevel: 5 [Tue Jul 31 11:35:53.923 2012] Starting system message bus: dbus. [Tue Jul 31 11:35:53.985 2012] Starting telnet daemon. [Tue Jul 31 11:35:54.016 2012] Starting syslogd/klogd: done [Tue Jul 31 11:35:54.048 2012] Starting thttpd. [Tue Jul 31 11:35:55.423 2012] [Tue Jul 31 11:35:55.423 2012] _____                    _____           _         _ [Tue Jul 31 11:35:55.454 2012] | _  |___ ___ ___ ___   |  _  |___ ___  |_|___ ___| |_ [Tue Jul 31 11:35:55.454 2012] |    |  _| .'|. | . | |   __|  _| . | | | -_|  _|  _| [Tue Jul 31 11:35:55.469 2012] |__|__|_| |__,|_  |___|  |__|  |_| |___|_| |___|___|_| [Tue Jul 31 11:35:55.469 2012]              |___|                    |___| [Tue Jul 31 11:35:55.469 2012] [Tue Jul 31 11:35:55.469 2012] Arago Project http://arago-project.org am335x-evm ttyO0 [Tue Jul 31 11:35:55.469 2012] [Tue Jul 31 11:35:55.469 2012] Arago 2011.09 am335x-evm ttyO0 [Tue Jul 31 11:35:55.469 2012] [Tue Jul 31 11:35:55.485 2012] am335x-evm login:

= PSP Linux Drivers =

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

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.
 * 7) Operation of both external ports as independent network interfaces
 * 8) VLAN and ALE configuration support

Features Not Supported

 * 1) Promiscuous mode of operation.
 * 2) IEEE 1588

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

TCP Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

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

iperf -s iperf -c &lt;server ip&gt; -w &lt;window size&gt; -m -f M -d -t 60 ethtool -C eth0 rx-usecs 500
 * iperf version 2.0.5
 * On PC Host invoke iperf in the server mode.
 * On the DUT iperf is invoked in client mode  (bi-directional traffic for 60 seconds).
 * Interrupt pacing feature enabled with pacing interval set to 500usecs.
 * DUT is connected to a gigabit network.

UDP Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

iperf -s -u iperf -c &lt;server ip&gt; -b -f M -t 60
 * iperf version 2.0.5
 * For receive performance, on DUT, invoke iperf in server mode.
 * For transmit performance, on DUT, invoke iperf in client mode.

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
 * 6) Only 8-bit NAND is tested since EVM supports only a 8-bit 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.

Note: The above data are obtained on EVM1.5 running 800MHz

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.

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 Extreme 64G Class 10 SDXC card)
 * File System: ext2
 * Partition was mounted with async option
 * On EVM1.5 running 800MHz

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


 * SD Card (Sandisk Extreme 64G Class 10 SDXC card)
 * File System: vfat
 * Partition was mounted with async option
 * On EVM1.5 running 800MHz

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
 * 4) USB Host Video Class (UVC)
 * 5) USB Host Audio Class (UAC)
 * 6) USB CDC HOST (USBNET)

Gadget mode


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

OTG mode
 * 1) Host Negotiation Protocol (HNP)

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 : Western Digital 1TB (My Book Essential) USB hard disk is connected to usb0 port. File read/write performance data on usb0 port is captured. For detailed test setup refer to USB MSC host test setup

USB MSC (MUSB) Host mode EXT2 File System Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

USB MSC (MUSB) Host mode VFAT File System Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

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 using a file inside /dev/shm as storage gadget media exposed as removable media to an Ubuntu 10.04 host over USB. The storage media is formatted as vfat filesystem. 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 USB MSC device setup

Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

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

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

USB CDC-DMA Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

USB RNDIS-DMA Performance
Note: The above data are obtained on AM335x PG 2.0 EVM1.5 running 800MHz

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
All the measurements below were done on the AM335x EVM Rev 1.5b. The definition of idle at Linux prompt is as per the tables shown below

At each OPP
This section indicates the power measured for all power rails at various OPPs (selected via ). The measurements were done with the  created using. Measurements were taken while Linux was idle at command prompt. The measurements were done using EVM revision 1.2A.

When suspended
This section indicates the power measured for all power rails when system is in suspended state (via ). The measurements were done with the  created using. Two sets of measurements were done, one without and one with I/O pad optimizations

In Stand-by
This section indicates the power measured for all power rails when system is in Standby state. The measurements were done with the  created using.