Raspberry Pi Forums

LdB

You don't have the core in baremetal at all, you need to stop referring to it as such. It's idling in linux with no tasks being scheduled to the core via affinity is all that is happening. The task switcher is clearly still active and the 1ms interrrupt is the reschedule tick. I just pulled up isolc...

LdB

Heater you still seem somewhat confused 1.) You need to understand how Interrupts work on linux can I recommend https://www.oreilly.com/library/view/linux-device-drivers/0596005903/ch10.html The irq signal itself and the processing of that irq are divorced in linux and you really need to understand ...

LdB

You are after a boot loader/manager they just install themselves in the master boot record and control things from there.. there are a truckload of them Wiki has a small list of what will be a very large list https://en.wikipedia.org/wiki/Comparison_of_boot_loaders The more modern way is UEFI https:...

LdB

I don't use linux a lot but according to the linux manual on boot parameters, so I apologize if wrong 'nosmp' and 'maxcpus=N' (Only when __SMP__ is defined.) A command-line option of 'nosmp' or 'maxcpus=0' will disable SMP activation entirely; an option 'maxcpus=N' limits the maximum number of CPUs ...

LdB

You obviously know how linux interrupts work so even if it routed to your baremetal core just take the interrupt ignore it and return, a few clock cycles. You control the core VBAR register so linux can go whistle dixie even if it did route you the interrupt. You usually have to provide coverage tab...

LdB

Sorry heater I missed that initial bit about the linux on the other cores, I just read the last couple of posts which were all baremetal and thought you were down the wrong path. But I suppose the main thing is not that so much removing any delays due to Linux but ensuring they don't affect the audi...

LdB

It will be always positive no matter if it is 32 or 64 bits. Label __code_start comes after virt_start hence it is placed at a higher address than virt_start that's what I understand from it. I will agree to disagree it isn't worth worrying about because I would do it that way never, so I really do...

LdB

Not tried it but I would imagine the official ARM pre-compiled should do the trick
https://developer.arm.com/tools-and-sof ... /downloads
Right hand side download the linux 64 bit version

LdB

Not following that heater.. what does any of that have to do with a Pi4 under baremetal (aka there is no liunx)?

LdB

I don't think it's correct. Checkout the kernel map file here (80009000 T __code_start) I had to sit and work that out and it works because the offset is a 32 bit integer and 0x80000000 is minus 2,147,483,648 That is why it's a subtraction minus a negative becomes a positive :-) So your section sta...

LdB

Can 3 cores run 64bit and one run 32bit? Yes but that would be rare and sort of silly given any Core in 64 bit can run a 32bit O/S or APP anyhow Same as on an Intel any 686, Pentium or whatever can still run old 386 code. It can even get more sophisticated than that https://en.wikichip.org/w/images...

LdB

I can add you do get hit occasionally by the "out of order execution" and you have WTF is that bug moments :-) The fun part is Disassembling https://static.raspberrypi.org/files/rpi-boot-eeprom-recovery-2019-05-10.zip The modified bootstub for the BC2711 is up in case anyone missed it https://github...

LdB

I can't make sense of some of what or why you want to do some things but i will answer what I can ttbr0 and ttbr1 have to be physical addresses they are the start point for locating the virtual tables. At assembler level the address of __code_start is simply something like ldr r0, =__code_start I am...

LdB

Yep so you have an original Pi3B not the newer Pi3B+.

So you can only flash onboard LED's thru mailbox if you want to use GPIO you have to have an actual LED on a GPIO port.

LdB

I am with what heater said if you really were going to mess around with this you might as well go for VS-CODE which is pretty dam amazing. If you want a web only solution go to VS-CODE start point the monaco editor. https://microsoft.github.io/monaco-editor/ Scott Hanselman has the script for VSCODE...

LdB

I started reading your posts from top ... you tried compiling for 64bit I take it you are on a Pi3 and you assembler has an address 0x3f200000 This is specifically Pi1, PiZero only ... it tells you on the text read it https://github.com/dwelch67/raspberrypi/tree/master/blinker01 If you open blinker0...

LdB

Problem bl main Main does no exist anywhere in your code. You have a notmain which is probably where you wanted to go (that is very David Welch he tends to use that rather than main like most). Change one or the other so it makes sense. You GPIO set routine is also fundementally flawed .. look at th...

LdB

Can we stop the confusion ... OpenGL and GLES are standards they say nothing for how you implement. https://en.wikipedia.org/wiki/OpenGL The OpenGL specification describes an abstract API for drawing 2D and 3D graphics. Although it is possible for the API to be implemented entirely in software , it ...

LdB

The ARM8 prefers natural alignment 8 bits can be any byte aligned 16bits it wants 16 bit alignment ( 2 byte) ... half word opcodes 32 bits it wants 32 bit alignment 64 bit can be 32 but it prefers 64 for speed Function arguments that are structs are padded to multiples of 8 bytes It can store and lo...

LdB

Code doesn't seem to do anything wrong on real Pi3, I get the message "made it this far" etc

What exactly goes wrong?

LdB

Can I send you some other stuff on videocore to document

... really nice writeup I can never make the time or effort.

I have worked out a pile of stuff with the Pi4 that I really need to do that sort of thing with but I am lazy.

LdB

Looks right now ... mine aren't much different bool gpio_output (unsigned int gpio, bool on) { if (gpio < MAX_GPIO_NUM) // Check GPIO pin number valid { volatile uint32_t* p; uint32_t bit = 1 << (gpio % 32); // Create mask bit p = (on) ? &GPIO->GPSET[0] : &GPIO->GPCLR[0]; // Set pointer depending on...

LdB

I think 0x200 is simply the vector table address you add the VBAR to it ... let me have a look Probably try moving where you set the VBAR down to when you have switched to EL1 rather than up in EL2 just in case QEMU has a bug. That is just a random thought I will take a look tonight. VBAR_ELn + 0x00...

LdB

No you can store a 64 bit register directly in memory so anywhere outside the peripheral bus is fine. The only things hard set 32bit is the peripheral bus specifically on the Pi3 anything between 0x3f000000-0x40010000 That is all the peripherals on this datasheet https://www.raspberrypi.org/app/uplo...

LdB

I would assume so but your write and read have same C pointer bug did you fix them?
Basically anywhere you used this "BYTEDIFF" is bugged

Yes this makes more sense

Code: Select all

if (pin > GPIO_PIN_LAST)

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