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by mrvn
Sat Jan 19, 2013 11:52 pm
Forum: Bare metal, Assembly language
Topic: VideoCore mailboxes
Replies: 16
Views: 3784

Re: VideoCore mailboxes

phil95 wrote: MemoryBarrier(), DataCacheFlush() are the classicals fu,ctions
Philippe
Would you mind sharing them?

MfG
Mrvn
by mrvn
Sat Jan 19, 2013 10:44 am
Forum: Bare metal, Assembly language
Topic: Do MMIO registers have to be read/written as 32bit?
Replies: 8
Views: 2330

Re: Do MMIO registers have to be read/written as 32bit?

I ment an example where gcc does the wrong thing. I vaguely remember something in the C standard that should prevent that and some quick tests show that access to parts/bits of an "unsigned long long" do get optimized into smaller reads but "volatile unsigned long long" sticks with reading the whole...
by mrvn
Sat Jan 19, 2013 12:00 am
Forum: Bare metal, Assembly language
Topic: Do MMIO registers have to be read/written as 32bit?
Replies: 8
Views: 2330

Re: Do MMIO registers have to be read/written as 32bit?

dwelch67 wrote:You most certainly and will find many examples that use volatile uint32_t*. My examples dont and I have here and there stated the reasons (I have many times gotten gcc (and others) to fail to properly generate the right instruction for volatile uint32_t solutions).
Can you give an example?
by mrvn
Fri Jan 18, 2013 9:31 pm
Forum: Bare metal, Assembly language
Topic: Do MMIO registers have to be read/written as 32bit?
Replies: 8
Views: 2330

Do MMIO registers have to be read/written as 32bit?

I noticed that all MMIO registers (like the UART) in examples are declared as 32bit and read/written through a special asm function or inline asm. What is the reasoning behind that? Why not simply declare them as volatile uint32_t? Also do I always have to read/write them as 32bit values? Since many...
by mrvn
Fri Jan 18, 2013 9:22 pm
Forum: Bare metal, Assembly language
Topic: Bare metal: What is the power on environment?
Replies: 21
Views: 6321

Re: Bare metal: What is the power on environment?

How about the video output? Will the GPU have activate and configured that already at that point? Do I just need to find the ATAG, look for the ATAG_VIDEOLFB and have all the settings there? Or do I need to mess around with the mailboxes first to get the GPU to initialize video output? ATAG_VIDEOLF...
by mrvn
Thu Jan 17, 2013 1:54 pm
Forum: Bare metal, Assembly language
Topic: Bare metal: What is the power on environment?
Replies: 21
Views: 6321

Re: Bare metal: What is the power on environment?

Thanks dwelch67 for that long reply. I had already found you treasure trove of examples but they sometimes lack a bit of documentation. For example the atags code says just: Derived from bootloader05. This is to demonstrate the contents of the r0, r1, and r2 registers when kernel.img is entered... R...
by mrvn
Wed Jan 16, 2013 6:27 pm
Forum: Bare metal, Assembly language
Topic: Bare metal: What is the power on environment?
Replies: 21
Views: 6321

Bare metal: What is the power on environment?

Hi, I'm completly new to arm and just recently got my RPi so please excuse my ignorance and feel free to throw any urls at me to read. What I'm wondering is what environment is defined when you turn on the RPi and your bare metal kernel gets control. So far I know the following (correct me if I get ...
by mrvn
Wed Jan 09, 2013 7:05 pm
Forum: Beginners
Topic: Does RPi support resolution of 2560x1440?
Replies: 5
Views: 40611

Re: Does RPi support resolution of 2560x1440?

We also have a pixels/second limit which is [email protected] which that monitor is likely to exceed.
How approximate is that? Does [email protected] work or not?

MfG
Mrvn

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