VRAM initialization for E4690 card

[alphabetagamma]

Hi
I am working on driver development of graphics card ATI Radeon E4690 having RV730 GPU.

I am able to register the device successfully on PCI. (read the device id correctly)

Just to test if I am able to write some chunk on VRAM, i tried something like this:
*(some_vram_addr)=someval;

However when I debug and try to see at the address, someval is not getting written. What I am missing here.
I am not even sure VRAM can be accessed this way.

Thanks

[bridgman]

I guess the two main questions are:

1. how much device initialization have you done? (if card is primary then VBIOS post may be sufficient, otherwise you can use the radeon kernel driver source as reference)

2. have you mapped the VRAM BAR so that you can access it (ie is "some_vram_addr" the location where you mapped it ?)

[alphabetagamma]

Thanks for the reply. I have not configured the DMA in my system.

Yes VRAM BAR is initialized properly. (I ve read it from 0x10 BAR 0 and I ve got the address at 0x60000000)

Is VRAM only accessible through DMA?

[bridgman]

The HDP (Host Data Port) allows the CPU to access a portion of the VRAM through the VRAM BAR, typically a 256MB window. If you see references to "visible VRAM" in the driver code that refers to the subset of VRAM which is CPU-accessible via the BAR.

Have you walked through the initialization code in the radeon kernel driver yet ? IIRC you will need pretty much everything it contains in your driver as well.

[agd5f]

If the card has not been posted (either by UEFI/legacy bios or driver), I don't think vram access will work.