[Intel-gfx] enabling forcewake from userspace

[Chris Wilson]

On Sat, 26 Mar 2011 08:46:25 -0700, Ben Widawsky <ben at bwidawsk.net> wrote:
> I think I won't bother trying to upstream my solution. But I'm also
> thinking we should make intel_reg_read/write print a warning/error if
> it's running on GEN6? What do you think?

Adding a code comment or an
if (IS_GEN6 && reg < 0x40000 && FORCE_WAKE == 0) printf("Muppet!\n");
is about as far as I would go. Certainly don't remind us on every
invocation.

> By the way, I do think the patch is beneficial just for kernel usage.
> Right now it doesn't matter, but as more users of the interface pop up,
> particularly in any time sensitive code... wouldn't it be awful if the
> GPU could powerdown while we're servicing an interrupt?

The GPU is definitely allowed to be powered down whilst the CPU is
servicing an interrupt. ;-) I take your point though that the current
method is not interrupt safe. However, we should not be doing such work
from an interrupt handler - if need be all the actual work is kicked off
from a workqueue.

Something we need to keep an eye on, but not a problem today. *touch wood*
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre