MHarrop678
Posts: 51
Joined: Thu Nov 27, 2014 8:36 pm
Location: Ipswich, UK

Baremetal document understanding

Sun Oct 30, 2016 11:37 am

I am attempting to get a better understanding of the documentation for the Raspberry Pi (More specifically the BCM 2835 document and the Videocore IV Architecture guide) but am having trouble.

I have followed the Raspberry Pi Cambridge bare metal lessons and have finished them, so now I would like to get to grips with how the author came to the conclusions he came to - With regards to GPU mailboxes, clocks and timers ect.

To give a specific example:
The author dictates that the base GPU mailbox address (Or read address) is 0x2000B880. From this we can derive all the other mailbox addresses. Where in the documentation is he able to derive this address from and how does he arrive at this conclusion?

I apologise if this seems like an odd question (Or if its been asked before) I would just like to gain a better knowledge in how to read this type of documentation so that I can derive my own answers in the future and ask (and answer) questions in a more informed way

piras77
Posts: 147
Joined: Mon Jun 13, 2016 11:39 am

Re: Baremetal document understanding

Sun Oct 30, 2016 10:38 pm

You may want to take a look at https://github.com/raspberrypi/firmware ... -mailboxes and linked pages.

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Ultibo
Posts: 161
Joined: Wed Sep 30, 2015 10:29 am
Location: Australia
Contact: Website

Re: Baremetal document understanding

Mon Oct 31, 2016 12:28 am

MHarrop678 wrote:The author dictates that the base GPU mailbox address (Or read address) is 0x2000B880. From this we can derive all the other mailbox addresses. Where in the documentation is he able to derive this address from and how does he arrive at this conclusion?
This particular case is probably not a good example because the mailboxes are not documented in the BCM2835 document. In this case the author of the Cambridge course gained that information from somewhere else, it is documented in the Linux source code here https://github.com/raspberrypi/linux/bl ... platform.h but not in the official Broadcom document.

That doesn't mean that your other questions are the same, it just means that sometimes the information comes from many different sources. This is one of the reasons we created the Ultibo project, so these things don't remain so mysterious to people starting their bare metal journey.
Ultibo.org | Make something amazing
https://ultibo.org

Threads, multi-core, OpenGL, Camera, FAT, NTFS, TCP/IP, USB and more in 3MB with 2 second boot!

MHarrop678
Posts: 51
Joined: Thu Nov 27, 2014 8:36 pm
Location: Ipswich, UK

Re: Baremetal document understanding

Tue Nov 01, 2016 2:43 pm

Cool, Thanks for your replies!

I really struggle to decipher the language that is used in the documents, they're not very straight forward. I guess it comes from my lack of experience with them and that I don't get to play with it day in, day out. I'm going to keep plugging at it though - I want to get this right.

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