Automotive Ethernet PHY bring-up: lessons learned and debug tips
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Control flowTelematikExpert systemMaß <Mathematik>Task (computing)Band matrixInfotainmentSoftware testingCoprocessorArchitectureGame controllerTranslation (relic)ChecklistAddress spaceFile formatSource codeSlide rulePhysicsStandard deviationSet (mathematics)Analog-to-digital converterHypermediaAsynchronous Transfer ModeVirtual machineInstance (computer science)Workstation <Musikinstrument>MereologyAddress spaceData managementAsynchronous Transfer ModeGoodness of fitNormal (geometry)InternetworkingPosition operatorLevel (video gaming)CuboidDiscrete element methodEndliche ModelltheorieComputer fileBus (computing)Ordinary differential equationQueue (abstract data type)WordOpen setTablet computerKey (cryptography)Power (physics)Slide ruleWave packetSoftwareMultiplication signQuantum stateSymbol tableMoment (mathematics)Physical systemCASE <Informatik>Density of statesBeat (acoustics)Game controllerExecution unitSoftware testingExpected valueUniqueness quantificationWebsiteOpen sourceView (database)ChecklistDressing (medical)Right angleINTEGRALDistanceVery-high-bit-rate digital subscriber linePresentation of a groupFrame problemAreaInfotainmentFile formatSoftware developerCartesian coordinate systemConfiguration spaceCoprocessorCountingLocal area networkStandard deviationSource codeData conversionHypermediaIntegrated development environmentSet (mathematics)Computer architectureExpert systemCategory of beingTerm (mathematics)CAN busBand matrixBootstrap aggregatingBitLine (geometry)Task (computing)Personal identification numberWhiteboardComputer animation
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Transcript: English(auto-generated)
00:55
Hello everyone, my name is Jean-Louis TK Carra, and today I'm here to talk about the bring up of Automotiv eternal advice
01:05
quick self introduction I'm an embedded Linux engineer since 2010. I Started to work in Paris in a company called open wide which is an open source consulting company and
01:20
Then later in Paris drones Then I joined Valeo Telematics here in Frankfurt area to develop TCUs TCUs are basically boxes Which connect your car to the internet over 4G now 5G network and also give you
01:42
positioning solutions based on GNSS and dead reckoning for instance I'm myself not an automotive expert. I Just want to share with you my humble experience Here are the goals and expectations You should know the basics about Ethernet PHY
02:02
in our case we will talk about Automotive Ethernet PHY, but the work should be the same for the standard Ethernet PHY You will have an overview of what task you should expect when you bring up an Ethernet PHY in an embedded Linux environment I will share also with you with you some common bring up issues and so debug tips
02:26
And this presentation is by based on an internal presentation I already gave last year in Valeo Corp Here's an agenda So first a very small slide about why we are talking about Ethernet in the automotive world
02:44
Then to be sure we are on the same line. We will define some technical terms and describe the basic architecture Then we will list all The PHY configuration everything you should know about your PHY
03:01
Before starting the actual software implementation then the software implementation itself and then some debug tips and questions, so Why do we have Ethernet in our vehicles? It's simple because we there is a need for always more bandwidth
03:23
Not only Software update use case, but you can think about Any advanced driver assistance systems and use cases and also infotainment etcetera There is also a need for standardization. There are already a lot of
03:43
competing solutions Which give you more bandwidth than the old Traditional Network like CAN flex-ray which give you only a few megabits So there are more competing solution like most for instance, but there are proprietary solutions
04:05
Why do we use? Automotive Ethernet and not standard Ethernet because in the automotive world you need to pass very strict Electromagnetic compatibility test and Automotive Ethernet allow you to allow you to do that
04:24
Because it's using only one twisted pair most of the time unshielded and So it has a it's very lightweight and it has a lower cost compared to traditional
04:41
Category five six Ethernet cable. So let's talk about some Technical terms so the PHY itself in the blue box here This is basically a transceiver. This is translating or more precisely. This is modulating your
05:04
Your data which are on the PCB on one side to the external world, which is just this twisted pair The MAC itself, so it's an Ethernet controller. This is integrated into your application processor
05:26
and This This MAC is controlling The Ethernet PHY over a dedicated control bus which is called MDIO bus. This is a low-speed bus with a clock of a few megahertz
05:45
Actually, it's not directly the MAC which is controlling your PHY over this MDIO bus. There is another entity it's called the STA or SME station management entity and Into your application processor, you could have many MAC many Ethernet devices, but usually only one
06:07
Station management entity And you have also the data bus high-speed data bus which could be for instance a GMII or RGMII Oh, I didn't say that but it could happen that on some application processor
06:33
For instance, I know I'm aware at least about some Qualcomm
06:40
processor they have the Ethernet PHY already integrated into the MAC I will talk more about this case. I know I work mainly with IMX8 processor So PHY configuration checklist
07:02
What is the PHY address? so This address is used by the MAC to find the PHY on the MDIO bus and start to talk with it The IEEE standard sets Up to 32 PHY on the MDIO bus as you can see in this example of
07:25
frame format sent over the MDIO bus are only five bits dedicated to the PHY address This PHY address is bootstrapped at PHY power-up Bootstrap basically it means you have for instance some resistors to some dedicated pins and at power-up the PHY is reading out
07:49
voltage on these pins and then it decides its own address and this is already Normally documented in your PHY data sheet and you need to check just your board schematic
08:02
another item What is the PHY mode master or slave? Most of the time you want your TCO to be in slave mode because your other end point in the vehicle Which could be an internet switch is in master
08:22
in our test setup when you are developing and bringing up your PHY you have Normally a device called media converter Which allow your PC to be a part of the local network of your TCU and Then you need to put this media converter into master
08:46
You can as you can maybe see on the slide the media converter is just basically one microcontroller in on one side you have the Automotive Ethernet PHY to connect your TCU and on the other side you have a standard
09:02
Ethernet PHY and RG45 connectors on our connector to connect your PC and this mode is of course always bootstrapped And you should ask yourself as well if the rest of the bootstrap configuration is consistent with your use case You can select the bandwidth 100 versus 1000 megabit the MII mode
09:25
Sometimes you can enable some delay internal delay in the PHY Etc and it can happen that you could even change the voltage level in software In your PHY so you should pay attention to that
09:41
So in general most bootstrap parameter that can be overridden later over the MDR bus during the PHY initialization over for Not only for fast bringer But in all the cases it's really recommended to use as much as possible the bootstrap method if you use case are not changing
10:08
So what is the init sequence for the PHY? At the beginning the PHY requires proprietary and under NDA initialization sequence which consists of a list of write sequence on the MDR bus
10:23
So writes write call or function looks like that you have the register the value and You have something called the dev add in Which can translate to device address
10:41
Be careful, this is not the PHY address it just because To make it simple on modern PHY You have a lot lot of register much more than what allow you Register address space here So you have also we can say kind of virtual devices inside the PHY and this dev add parameter
11:06
Gives you an additional level of indirection to to access these internal devices There are historical reasons for this So here just an example you have a kernel function called PHY write and then
11:24
You have the dev add register value and you one could imagine you put all this PHY write enrolling in a loop and this is your init sequence It must be really carefully selected. It's a source of confusion You need to triple check this init sequence with your vendor. It must match exact revision
11:47
Even if you have different variant like engineering sample 1, 2 and then the mass production sample It could change over the life early life of your internet PHY
12:02
There are two places to start the software implementation The bootloader which could be uboot for instance And then the kernel unless you have a very specific use case and you need to have network Access from the bootloader you can implement only the kernel. This is what we do most of the time
12:28
Anyway, the kernel level implementation is always needed for obvious reasons And if you implement it only in the if you implement it at two places
12:41
Then when you have some software update maintenance, you need to update at both places. So Quick reminder the MDO bus is controlled by the MAC driver This is provided by the your vendor BSP and thus this MDO bus control should work out of the box
13:01
You are not expected to do any implementation on debug at this level About close 22 close 45 you have already you had already an overview of what frame look looks like on the MDO bus
13:22
I Will not cover this in this presentation, but there are references at the end that you can invite you to follow basically, there are PHYs which Understand only close 22 format. Although they are close 45, but this is backward compatible So you can talk to them in a special close 22 indirect mode
13:45
It depends on your PHY Most of the time is state-of-the-art today that if your MAC can only talk in close 22, you can always somehow Find your way to talk to the Ethernet PHY. So let's list the remaining work
14:05
First step you need to adapt your board hardware description on device 3 in the Linux world You need to adapt an existing PHY driver or write your own PHY driver Then check that the PHY is detected and your drivers correctly loaded and finally check and debug
14:24
Your link which needs to be up, of course to start to do actual communication so for instance if we take an example here This is based on MX8. You have a block describing your
14:43
Your MAC device so it could be called FEC in MX world but Qualcomm processor, it could be EMAC for instance, of course needs to be activated Then the PHY mode attribute needs to be correct Here you can notice it's not only RGMIi versus AGMIi or just MI
15:05
You have kind of variance suffixes here in this case This suffix is telling the MAC to not put any delay inside because I'm already managing myself the delay in hardware in the PHY itself
15:22
for instance After that you have another block here which is describing your PHY and You have also Most of the time as far as I know there is only one PHY for one MAC you have this PHY handle which is pointing at
15:43
this PHY Here you need to check that the PHY address is correct so this is a reg attribute here and my physical address is 10 and For more details, of course, you have the documentation of the device tree itself
16:01
And so Ethernet PHY and so you have of course the documentation of your own MAC driver After that you need to locate the PHY driver there in driver net PHY What is recommended because
16:22
unfortunately most of the time the new your new Shiny automotives are net PHY driver is it's not Existing in the main line. So what is recommended even by our chip manufacturer is to locate one
16:40
Existing driver Which looks like the most to your to the drive to the PHY you want to to implement One effective way to locate Similar PHY would be to to grab the PHY ID which is a unique identifier of your PHY which is
17:05
Stored inside the PHY itself in the standard register 2 and 3 And then when you find a good candidate, you can start to use it. So you can if possible reuse Sometimes you can reuse existing function
17:22
If you don't find any Anything you can open a new new file or just modify your driver form at least the same brand
17:40
So when you open your PHY driver You need to define the PHY ID you have the PHY mask and so which helps you to map to map and to to match basically the PHY ID you are finding on the bus and You have also You need to give a name which is then later
18:02
displayed in the kernel messages, so you are you are sure your driver is actually Loaded and then you have what we can call primitives Routines which are used by the standard PHY Framework or by your Mac driver, sorry and
18:23
For instance you have some primitives like config init that need always to be rewritten Config init is a good place where you can put your PHY init sequence for instance You can reuse other which are very standard for instance soft reset here
18:40
it's using a already Define a PHY reset routine here, but behind that it's it could only Set one standard bit to reset the PHY And then you don't you don't have any specific soft specific specific PHY reset sequence
19:03
Because it's very generic and most of the PHYs they respect the standard About config init, this is called immediately after reset. And so this is where you put your init sequence. You can put also any other parameter enforcement like master, slave for instance or the custom parameter
19:24
so one effective way to do so is to put your init sequence in an array of strict and Providing the fact that all of this Register and value right there on the same dev addy you can put them in loop like that and that's it you have your init sequence
19:51
About config auto-negotiation in my experience In our own use cases We are not using auto-negotiation
20:02
By the way, this is Defined in the IEEE standard as optional in automotive, isn't it? This is optional some PHYs they don't even implement auto-negotiation Some claims they support auto-negotiation, but it doesn't work also. So one effective implementation
20:24
Is just to set this one line code You set the speed of your PHY device To one gigabit for instance, and that's it. You have you have you have it
20:41
For Other primitive like suspend resume, soft-relate etc unless Your PHY team leader has a really explicitly defined routine. For a PHY's bring up, it's safe to not implement them There in the PHY driver framework, there are generic implementations that are automatically used
21:01
Normally to get PHY up and to have your first link up Correct init sequence is all you need For Better detailed description of all the primitives. I invite you to check this header PHY to include Linux PHY.h
21:26
so Check the PHY's detected So if everything works, you have an attached PHY driver message and the name the string of the PHY name you put in the driver
21:41
If you have an hardware failure or just a bad PHY address you will have MDA device At address 10 is missing for instance and unable to connect to PHY Sometimes the PHY is found on the on the bus But your PHY driver is not loaded because for instance of an incorrect PHY ID. In this case
22:03
There is a generic PHY driver, which is loaded. In my experience, you cannot do much with this generic PHY Then You need to check the link is up Of course, you can check on your media converter or with IP command on Linux
22:21
Command source of link issues Your PHY init sequence is incorrect. In this case, it's not so easy to debug But you can always contact your FIE The other endpoint is not in master when the PHY is in slave or the other way around and
22:48
You have a delay issue You can you can put a delay, internal delay in the PHY or in the MAC But never at both side
23:00
I bought usually but never this is what has been recommended by our chip manufacturer as well and And I'm not a specialist of this topic, but you should ask your you know, prefer the automotive hardware engineer
23:22
You could have an hardware issue on the physical channel itself or just after Just after your PHY and before the connector, you have some components which are there to to help basically to pass the Electromagnetic compatibility test and so on
23:42
for instance You have a component called CMC command mode shock, which could be Which could not work broken just broken physical channel Let's talk about some U-Boot patch
24:01
When you are using a MX8 and you have a gigabit file You need to make sure you have this define set if you see quick in that MAC Otherwise you have one specific bit which is not being set correctly In the MAC, in one of the MAC registers
24:22
This define is by default already set in some board configuration in U-Boot it include config.h But it can it could be that you don't have that in your own board or the board you are describing or writing yourself so actually
24:41
recently since last year This patch, this define is now set one level above in one of the top level MX8 header So you should have no worries Unless you are using You know that on in the MX8 world you are using a fork from U-Boot
25:02
U-Boot dash MX8, no U-Boot dash MX, which is managed by by NXP and it's host on code Aurora So you might not have always the latest U-Boot coming with your MX8 BSP Sometime you you could have a file that needs your custom reset procedure
25:25
I forgot to say that about the init sequence sometimes Some File manufacturer give you just a PDF file with all the register that you need to write yourself Some other manufacturer, it was the case for me from Marvel, they give you directly a C source code file
25:42
Which can be easily integrated And in this case I had a I talked already about this use case in Linux, but at U-Boot, it's a generic file reset routine
26:01
it gets unconditionally called and I bought a small patch to allow to write your own custom file reset and By the time you see this video, maybe it will not be already proposed upstream but close for T5 support At
26:20
First when I asked for it, NXP told me they didn't want to support it officially But finally a little bit later I Observed that they push the support at Linux level only, so it's not in U-Boot in the meantime, they gave me
26:40
An official patch that I tested at U-Boot level and it worked so I plan to To Upstream it If possible in the near future At the next level, nothing special, as I said Close45 if you want to use it
27:00
It's already in the kernel since 2019 Some debug tips There is a very useful command line called phytool Here an example Where I'm reading the standard register to entry to check the PHY ID for instance
27:25
so first parameter is your PHY device name, sorry, is on a device name, then you have the Address physical address of your PHY and then the register PHY tool is using the MAC driver and it is functional only when the PHY is correctly detected
27:46
When you have such an error to connect to PHY It's not usable, so you can use it to debug some link issue But not for PHY detection itself One alternative you want to send arbitrary command on the MDAO bus, one alternative that I'm aware of
28:06
Maybe there are more, is to use the U-Boot environment where you have MDAO MII test command It requires of course a minimum of BSP integration, if you do everything at Linux level and you have the bare minimum at U-Boot For your board, it could not work out of the box
28:29
Another debug tip If you have no clue about what's happening and you really want to check that your PHY chip is alive Normally as soon as it's programmed up
28:43
In RGMII mode for instance, this is the one I debug the most Your PHY is supposed to produce automatically a RX clock at 25 MHz Or 125 MHz depending on your speed
29:04
You should check also the clock symmetry, you could have a clock asymmetry The RX clock which is produced by your PHY should be the same as the DX clock produced by the MAC So 25, 25, 100, 25, 100, 25 If you have a doubt and you want to check that the MDAO bus is currently managed by your MAC
29:27
With the scope, it's very easy. As I said, it's a 2 MHz By default, in my case it was maybe 2, 3 MHz and I think the standard set it up to 12 MHz And here you can observe the first frame on the scope
29:41
In this case, for instance, it's one of the first time I try to talk with a Close45 MAC PHY and I try to talk with it using Close22 and not the indirect mode The compatibility mode So after the turnaround time, the PHY did response 0
30:04
So sometimes it doesn't response It will release a line and sometimes it responds 0 So that can happen when you are talking to a Close45 PHY using Close22 Just an example
30:24
And something really useful is that at the beginning, you can see the start bit which differ between 22 and 45 So you can immediately check that your MAC is talking the correct frame format Another debug tip
30:43
I talked already about media converter to connect your developer PC to the local network of your TCU Sometimes it's better to use a PHY evaluation kit from the achievement door, which is also itself a media converter
31:02
But at least it's using exactly the same PHY, the same revision that the one you are trying to bring up Why? Because some early sample like engineering sample you might use during bring up phase They are not always immediately fully compliant with the standard, the open-alien standard for Automated Ethernet
31:25
And they are not interoperable with each other So for early bring up, you might ask or just use directly if you can take a PHY evaluation kit from the achievement door, if you can
31:45
Here are some reference links about the MDIO Close22 45 Very useful invite you to read them And if you want a generic Ethernet PHY introduction, more kernel-level oriented You can find this file in the documentation of the kernel
32:05
documentation-networking-phy.txt And that's it I hope you enjoyed the presentation and that it will help you to bring your own PHY Thank you
32:35
That people can ask questions and get responses from you
32:41
Unfortunately, it looks like so that so far we don't have any questions yet We still have plenty of time
33:05
I see one question from Luca Yes, okay So you mentioned the RXTX delays that the PHY or the MAC can add How do you know the delay values? Is there any auto-tuning, auto-training feature? A standard procedure to measure the required delay?
33:23
I'm not aware of any auto-tuning or auto-training feature that we can imagine To be honest I didn't really, I cannot really answer that question I managed to do it without any delay, but normally it's your hardware engineer which is designing your PCB
33:45
We can answer that question, but I know that in software, you know, you need absolutely To not put a delay at both sides. That's what I know I'm sorry Let's thank for the question
34:04
Yeah, in my experience that it's usually It doesn't work well at full speed if the delay is wrong, but Apart from that, it depends on the PCB layout Yeah, exactly
34:52
You're welcome Fabien
35:29
I don't know if it's visible in the in the stream that will be recorded, but TPWAT
35:44
TPWAT I don't think the chat will be available in the recording. So it's always a good idea to repeat questions
37:24
Okay, one question from Teresa Since there are no other questions, can I ask if automotive internet is changing and how closely do you monitor standards, communication standards? I worked in auto years ago and remain an IEEE member
37:43
So even if you are not part of If you are not a member of IEEE, there is another Committee, it's called Open Alliance And here in my component value My colleague Which is a hardware engineer is
38:03
Actively following all the news and coming out of this Open Alliance Committee We are already I think ourselves part of this committee and this is a way for us to to stay close to all the news
38:21
So the answer is basically be part of the Open Alliance
41:40
Gert, what should we do? It seems there is no other question
41:44
Well, we still have the room until 2 30 Okay And even after that here we can continue in a private room, but I don't think there will be a need for that Okay
42:37
Ankur wonders if ethernet has a future in automobile because all
42:42
He sees is that there was CAN, FlexRay and LIN I think it's going slow in a sector like automobile. CAN itself is already quite old Yes, I think they are all prisons on this on the buses
43:00
But for the for ethernet, I don't I don't remember if I said if I said it but it already Went into a mass production, I think in 2008 in BMW car Luxury car, but now I think it's it's It's coming everywhere
43:21
Yeah, usually this thing starts in the high-end cars first, yeah exactly looks like a car but Like CAN, Dr. Poirier was first in the Mercedes S-class if I remember correctly Was it in the end of the 80s or something like that?
44:02
There's another question from Teresa About what's the difference between auto and computer communications? What's the coolest component you use? well As I said If I'm only it's a generic question or only on ethernet question because on ethernet question as I said
44:24
It's a physical medium standard, which is different basically 10,000 base T1 or TX or T And so on but they're all ethernet and then the physical medium change This is how many is the difference but behind that it's always an ethernet
44:43
Auto-call, okay but then If it's a more general question, maybe you can elaborate Teresa It's communication inside the car itself or between car for instance
45:15
Okay, I will answer first. What's the coolest component you use? What's the
45:24
Newest components that we have in automobile communication are basically v-tweaks, vehicle to everything which is using as a As a layer radio layer it can use the wi-fi or mobile network
45:46
And you have also yes 5g modem that are the coolest component Our very precise GNSS module so we have now which allow you to have a centimeter resolution
46:06
Speaking about ethernet specifically I find this automotive very interesting because it manages to do With just the two wires. Yes And i'm wondering whether that will Show up in other areas as well
46:21
In buildings, it's probably Not going to happen that soon because they're already equipped with the eight wire Cable infrastructure anyway I wonder myself also the same question. Why do we not have uh, the automotive also internet
46:43
In the building and so on One of the one of the first answer is that uh, you are not allowed to have a so long cable using uh, automotive Basically, it's around 15 meters But you don't care in the automotive to to use a 100 meter long cable
47:04
Yeah, I don't think I have that long cables in my house Yes, but then you need to uh, yes Then you need to have a media converter in your house It's like people who are using a fiber optical for their land network. They need also to put everywhere
47:23
transceiver And uh, Teresa is asking another question, but uh, I'm afraid they cannot answer all of them So What is the wildest, uh
47:41
specification crazy current weird package our electric vehicle requiring Many for different parts than ic Um She's remembering, uh An igbt. I don't know. What is it for 55? 25 amp ampere
48:01
And the break unit in merced in breakthrough Good I'm, I'm not so specialist in automotive as I said, uh, i'm here in vallejo since three years And the mati has another question for you if automotive and software
48:23
They always bring safety and bureaucracy to my mind. Is this visible at your work, too? Well
48:40
Yes, yes, there is one thing, uh Which is If I feel it correctly and understood it correctly In automotive world you have the car manufacturer they are leading the way they are the master The king of the world and then you have the tier one tier two. I mean the different
49:03
Car equipment manufacturer and what I know is that they are driving some very strict standard Uh, it's um Uh, it's basically not bureaucracy, but it's just uh, uh project
49:21
Very strict project management standard with requirement and so on and so on Risk management, etc So yes, it is visible in my work. I am myself most of the time working, uh, not directly with uh,
49:41
A project which are already in mass production. I'm at uh some rnd level so I have more Freedom let's say and uh I don't feel this, uh pressure on my shoulder all the time But when i'm working also from time to time to help mass mass production, uh
50:03
And uh project project then yes, it's visible
53:02
So Luca has another question about uh A to b automotive audiobus and he's wondering whether it's gaining adoption on real world automotive Uh, yes, so luca, uh At least I I saw a to b, uh components on uh on uh
53:22
On some pcb. Uh, I saw on some schematic. I didn't work personally with it. But uh recently yes, I saw it Uh in some project so yes, it's gaining a traction I think it's also part of some requirements from some car manufacturer even if i'm not working directly
53:42
During the rfq phases I know it's gaining adoption Yes
55:02
Either has a question about the reference clock Which is an input to both the mac and the phi And he's wondering if you've ever seen a device that generates the clock Uh And either if you do you mean that it's a clock, uh,
55:21
clock signal, uh for the Rgmi, uh, data bits I I never saw any other device that generates the clock. There is a mac and the phi On one side and the other but no, I never seen a device that generates the clock Uh, i'm aware of the eric's clock and tx clock when using lgmi
55:43
When using sgmi, I think there is no such Uh clock i'm not sure um No About that The fact that I don't I never seen uh, I never seen a device that you know had such clock. I don't know
56:08
Yes 15 Uh So, yeah, i'm not very familiar with mii I don't know if it's still uh widely used So I assume it's it's what it's just uh, one and one megabit maybe sorry
58:52
You are mute get You are mute So What he has a final question about automated drivers assistance and internet and safety with linux
59:09
Oh, yes Once that be safety concern as far as I know We are not We are not using a specific real-time linux or something else in our tcu and it's not