Using PCIe® in Mobile Devices
Ofer Rosenberg
Senior Staff Engineer
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Used by PCI-SIG under license

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Disclaimer
Presentation Disclaimer: All opinions, judgments, recommendations,etc. that are presented herein are the opinions of the presenter of thematerial and do not necessarily reflect the opinions of the PCI-SIG®.

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Contents
 Introduction: PCIe® at Qualcomm Technologies Inc. (QTI)
 Case Study – PCIe in MDM

 QTI PCIe Perspective

Qualcomm Snapdragon is a product ofQualcomm Technologies Inc.

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PCIe Importance to QTIQTI ships around a Billion Application Processors each year Each has one or more PCIe Root Complexes Key interface for communicating with Modem/Wi-Fi devices

QTI ships XX Modem devices each year Connect as PCIe end-points
 Key interface for connecting the device to QTI or 3rd Party Application Processors

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4Motivation
 Few years ago, QTI identified the need for long-term solution for highspeed Chip-to-Chip (C2C) connection
 Modem, Wifi and Storage speeds increase Existing serial interfaces speed became a bottleneck Needed a long term, evolving, high speed interface which will meet future
speed increase
WCDMA

TPT(bps)802.11a802.11n(20MHz)802.11n(40MHz)802.11ac(wave1)802.11ac(wave2)

54M

300M

600M

1.3G

6.7G

HSPALTEHSPA+
CAT 3CAT 5

CAT 10Max DLrate (bps)

384K

14M

28M

100M

300M

450M

Max ULrate (bps)

128K

5.7M

11M

51M

75M

100M

 PCIe was chosen due to its extendibility, design philosophy, features andpower management capabilities
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PCIe at QTIQTI develops both Root-Complex and End-PointRoot Complex:
 Qualcomm® Snapdragon™ Application Processors provide
PCIe Root-Complex Port/s
 Qualcomm Server Chips will arrive with Multiple RootComplex PortsEnd-Point: Qualcomm® Gobi™ Modems connect as PCIe EP WLAN Devices connect using PCIe EP WiGig Devices connect using PCIe EP Other…

QTI Three Pillarsof PCIe use

High-End
C2C

Embedded/MobileC2C

High-End
ExpansionBus* Qualcomm® Gobi is a product of Qualcomm Technologies Inc.
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Mobile Device Chipset
PCIe
Audio
Codec

Modem
Application
Processor

Storage

Wi-Fi

CameraWiGig
Display

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Case Study – PCIe in Mobile
Data Modem (MDM) Chipset(at system level,including PCIe L1ss)

PCIe
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PCIe in Mobile Devices
Example for Common Usage:
 Application Processor connected to External Modem Samsung Galaxy Note 4

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“Smart” Devices Advantage
 PCIe devices are “smart”
 Access different entities inside the SoC (pending on access rights)
 Autonomously handle data transfers (reads and writes)
The Direct & Autonomous access has SoC power management advantages
 Access Modules & DDR without waking the CPU Access Modules with standalone memory without waking the DDR

DDR

Mem
Interface

Modem
ChipsetCPU

Module B

Module A
RAM

SMMU

PCIe
RC

PCIe
EP

Application Processor
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Typical LTE Activity
 LTE works in “Bursts” of 1mSec
 The device issues a burst of data write (downlink) and read(uplink), and then remains silent until next subframe Burst length depends on generation (CAT 1 - 10)
 Ideal for smart devices which know to handle power states …
subframe – 1mSec

#0

#1

#2

#3

…

#18

#19

Radio Frame – 10mSec

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CAT 1

CAT 2

CAT 3

CAT 5

CAT 10Max DLrate (bps)

10M

50M

100M

300M

450M

Max ULrate (bps)

5M

25M

51M

75M

100M

©2015 Qualcomm Technologies, Inc. All Rights Reserved.
Used by PCI-SIG under license11PCIe Power States
Link
Initialization

L3
Power ON
Power OFFActive
L0s

EIOS
FTS

Tx Idle

L0

L2/L3
Ready

PM Msgs.

WAKE#ASPM
Msgs.

Vaux

L2

Link
RecoveryL1(L1.0)
CLKREQ#
De-Assert
LTR < Threshold

PLL /PIPERX IdleDetectTx Comn
L1Mode

L0

On

On

On
Substates

L1.0

Off

On

On

L1.1

Off

Off

On

L1.2

Off

Off

Off

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CLKREQ#
De-Assert
LTR >= Threshold
CLKREQ#
Assert

L1.1

CLKREQ#
AssertL1.2©2015 Qualcomm Technologies, Inc. All Rights Reserved.
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12Race to Idle Philosophy
The Basics
 Resume
 Transmit as fast as possible(PCIe 1/2/3 …)
 Go back to low-power state

L0
L0àL1.0
L1.0
L1.0àL1.1

L1.2àL0

L1.1



L1.2

The Challenges
 Buffering UL/DL sync
 Correctly Select L1.1 / L1.2

1mSec

.

1mSec

.

1mSec

PCIe Link

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System Perspective
 PCIe Link inactivity
 Short intervals, such as 1mSec frames
 Longer intervals due to data link inactivity
Host & Device in
Low Power Power management is a joint HW-SW effort
 HW manages short interval transitions (L1ss – L0)
 Host / SW manages deeper transitions (D0 – D3/L2)

Host : Low Power
Device : Low Power
PCIe : D3cold / L2
Deviceenters/exists
Low power

Device in
Low Power

NormalOperation

Host inLow Power

Host : ON
Device : Low Power
PCIe : D0 / L1ss

Host : ON
Device : ON
PCIe : D0 / ASPM

Host : Low Power
Device : On
PCIe : D3cold / L2

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Deviceenters/exists
Low power

Hostenters/exists
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SUMMARY

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QTI PCIe Perspective
Full-Fledge PCIe topology
Host CPU

Application Processor

PCIe Root

PCIe Root

PCIe Root

PCIe Switch

PCIe
EndPoint

PCIe
EndPoint

PCIe
EndPoint

PCIe
EndPoint

PCIe Switch

PCIe
EndPoint

QTI Mobile typical usage

PCIeEndPoint

PCIe Bridge

PCIAdapter

PCIe
EndPoint

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PCI-XAdapter

 Single Bus/Device per RC
 (Very) Short links
 Frequent switch between
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QTI PCIe Perspective
 What do we like in PCIe ?
 Highly extendable interface, from 2.5 GT/s x1 to 8 GT/s x16
 Philosophy of “Smart” devices:– Initiate data transactions– Handle power state changes

 Advanced capabilities (TC, MSI, TPH, ATS, IOV and more… ) Low-Power States What would we like to enhance in PCIe ?
 Optimized behavior for Low-Power / Chip-to-Chip scenarios– Revisit Legacy features (such as ECAM)– Revisit LTSSM, up/down link time, etc.

 Enhanced support in interconnect fabrics– Example: Ordering Rules

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QTI Vision for PCIe
 Power States transitions cleanup (redundantstates, reduce min. duration)
 Improve Support in Advanced System Buses Optimize Chip-to-Chip scenarios
 Standardize handling of Host power states More…
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TIME FOR QUESTIONS…

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Disclaimer

Qualcomm Snapdragon™ and Gobi™ are trademarks ofQualcomm Incorporated, registered in the United States andother countries, used with permission.
Other product and brand names may be trademarks orregistered trademarks of their respective owners

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Thank you for attending thePCI-SIG Developers Conference
Israel 2015
For more information please go towww.pcisig.com
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