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Using PCIe® in Mobile Devices
Jim Panian
Director, Technical Standards
Qualcomm Technologies, Inc.
©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.
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Disclaimer
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Presentation Disclaimer: All opinions, judgments, recommendations,
etc. that are presented herein are the opinions of the presenter of the
material and do not necessarily reflect the opinions of the PCI-SIG®.
©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.
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Introduction: PCIe® at Qualcomm Technologies Inc. (QTI)
Case Study – PCIe in MDM
QTI PCIe Perspective
Contents
Qualcomm Snapdragon is a product of
Qualcomm Technologies Inc.
©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.
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PCIe Importance to QTI
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QTI ships around a Billion Application Processors (AP) each year
APs have 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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Few years ago, QTI identified the need for long-term solution for high-speed 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
PCIe was chosen due to its extendibility, design philosophy, features and power management capabilities
Motivation
WCDMA HSPA HSPA+ LTE
CAT 3 CAT 5 CAT 10
Max DL
rate (bps)384K 14M 28M 100M 300M 450M
Max UL
rate (bps)128K 5.7M 11M 51M 75M 100M
802.11a 802.11n
(20MHz)
802.11n
(40MHz)
802.11ac
(wave1)
802.11ac
(wave2)
TPT
(bps)54M 300M 600M 1.3G 6.7G
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QTI develops both Root-Complex and End-Point
PCIe at QTI
QTI Three Pillars
of PCIe use
Root Complex:
Qualcomm® Snapdragon™ Application Processors provide PCIe Root-Complex Port/s
Qualcomm Server Chips will arrive with Multiple Root Complex Ports
End-Point:
Qualcomm® Gobi™ Modems connect as PCIe EP
WLAN Devices connect using PCIe EP
WiGig Devices connect using PCIe EP
Other…
* Qualcomm® Gobi is a product of Qualcomm Technologies Inc.
©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.
Embedded/Mobile
C2C
High-End Expansion
Bus
High-End C2C
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Mobile Device Chipset
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Application
Processor
Modem
Wi-Fi
Audio
Codec
PCIe
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Camera
Display
Storage
WiGig
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Case Study – PCIe in Mobile Data Modem (MDM) Chipset
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PCIe
(at system level,
including PCIe L1ss)
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Example for Common Usage:
Application Processor connected to External Modem
Samsung Galaxy Note 4
PCIe in Mobile Devices
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Example for Common Usage:
Application Processor connected to M.2 card embedded in a notebook or tablet
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PCIe in Mobile Devices
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M.2 Card
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PCIe “Smart” Devices Advantage
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Application Processor
Modem
Chipset
SMMUModule AModule B
CPUMem
InterfaceDDR
RAM PCIe
RC
PCIe
EP
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
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PCIe Low Power Advantage
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 …
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CAT 1 CAT 2 CAT 3 CAT 5 CAT 10
Max DL
rate
(bps)
10M 50M 100M 300M 450M
Max UL
rate
(bps)
5M 25M 51M 75M 100M
#0 #1 #2 #3 #18 #19…
LTE Radio Frame – 10mSec
subframe – 1mSec
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PCIe Link
1mSec . 1mSec . 1mSec
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PCIe Power States
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L1Substates
L1.2
L1(L1.0)
CLKREQ#Assert
L1.1
CLKREQ#Assert
L0L0sL2/L3 Ready
L3
L2
Power OFF
Vaux
PM Msgs.
Power ON
WAKE#
EIOS
FTS
Active
ASPMMsgs.
LinkRecovery
Tx Idle
LinkInitialization
CLKREQ#De-AssertLTR >= Threshold
CLKREQ#De-Assert
LTR < Threshold
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PLL /
PIPE
RX Idle
Detect
Tx Comn
Mode
L0 On On On
L1.0 Off On On
L1.1 Off Off On
L1.2 Off Off Off
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Race to Idle Philosophy The Basics
Resume
Transmit as fast as possible (PCIe 1/2/3 …)
Go back to low-power state
The Challenges
Buffering
UL/DL sync
Correctly Select L1.1 / L1.2
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PCIe Link
1mSec . 1mSec . 1mSec
L1.2
L1.2 à L1
L1
L1 à L0
L0
L0 à L1
L1
L1 à L1.2
L1.2
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System Perspective
PCIe Link inactivity
Short intervals, such as 1mSec frames
Longer intervals due to data link inactivity
Power management is a joint HW-SW effort
HW manages short interval transitions (L1ss – L0)
Host / SW manages deeper transitions (D0 – D3/L2)
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Normal
Operation
Host : ON
Device : ON
PCIe : D0 / ASPM
Device in
Low Power
Host : ON
Device : Low Power
PCIe : D0 / L1ss
Host in
Low Power
Host : Low Power
Device : On
PCIe : D3cold / L2
Host & Device in
Low Power
Host : Low Power
Device : Low Power
PCIe : D3cold / L2
Device
enters/exits
Low power
Host
enters/exits
Low power
Device
enters/exits
Low power
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SUMMARY
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QTI PCIe Perspective
Full-Fledge PCIe topology QTI Mobile typical usage
Single Bus/Device per RC
(Very) Short links
Frequent switch between Active & Low-Power
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Host CPU
PCIe Root
PCIe Switch
PCIe
EndPoint
PCIe
EndPoint
PCIe Switch
PCIe
EndPoint
PCIe
EndPoint
PCIe
EndPoint
PCIe Bridge
PCI
AdapterPCI-X
Adapter
Application Processor
PCIe Root
PCIe
EndPoint
PCIe Root
PCIe
EndPoint
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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 (3.0)
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
Enhanced support in interconnect fabrics
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PCI-SIG under license.
1718
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TIME FOR QUESTIONS…
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PCI-SIG under license.
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Disclaimer
Qualcomm Snapdragon™ and Gobi™ are trademarks of Qualcomm Incorporated, registered in the United States and
other countries, used with permission.
Other product and brand names may be trademarks or registered trademarks of their respective owners
20©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.
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Thank you for attending the PCI-SIG Developers Conference 2015.
For more information please go to www.pcisig.com
©2015 Qualcomm Technologies, Inc. All Rights Reserved. Used by
PCI-SIG under license.