Re: [PATCH 3/3] alpha, drm: Add Alpha support to Radeon DRM code

Hi, Dave,

It is the explanation that is inaccurate; I was still thinking about mmap when
the new paradigm is to do the mapping when the VM faults.

I believe the code that requires this patch is: ttm/ttm_bo_vm.c: ttm_bo_vm_fault(),
specifically:

    for (i = 0; i < TTM_BO_VM_NUM_PREFAULT; ++i) {
        if (bo->mem.bus.is_iomem)
            pfn = ((bo->mem.bus.base + bo->mem.bus.offset) >> PAGE_SHIFT) + page_offset;
        else {

The "pfn" needs to reflect the correct system bus address to get to the VRAM
on the graphics card.

I will rework the commentary and resend.

Thanks for the feedback.

Jay


On 06/13/2011 07:35 PM, Dave Airlie wrote:

On Fri, Jun 10, 2011 at 8:20 AM, Jay Estabrook [off-list ref] wrote:

quoted

Alpha needs to have the system bus address for the device's local
memory available, so that it can be returned to user-level, where
it may be used in an mmap(). So, we make bus.addr hold the ioremap()
return for kernel use, and then we can modify bus.base appropriately.

I don't get this. why is mmap passing in an address? we don't do that anymore.

When you mmap the device node it passes back a hashed offset in the
table, that the
kernel then translates into a proper address and sets up the page tables.

So I really don't get what this patch is doing, either the
explaination of what it is doing is wrong
or it is wrong.

Dave.