Re: [PATCH] [RFC] drm/i915: Warning when reads or writes are dropped

[Chris Wilson <chris@chris-wilson.co.uk>]

On Tue, 17 Jan 2012 12:08:57 +0100, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Fri, Nov 04, 2011 at 05:03:54PM -0700, Ben Widawsky wrote:
> > The GTFIFODBG register gives us 3 error types when the fifo is accessed
> > and full. Whenever we do a forcewake_put we can check this register to
> > see if any of the CPU related errors occurred.
> > 
> > Of more interest is perhaps the bit I am not checking which tells when
> > some other part of the chip makes a request and the FIFO is full. I
> > couldn't really decide on a good place to put that check.
> > 
> > This patch seems to have value to me, but I'm not sure it's worth the
> > cost of the extra MMIO read`. (I've yet to see this occur, but I haven't
> > actually been running with it for very long).
> > 
> 
> This looks like a nice little patch here. Care to update it for
> spinlocked and multithreaded forcewake and maybe also check the other
> errors? And also add it to the error_state output (just base it on top of
> danvet/my-next to avoid conflicts with the oustanding error_state
> cleanup).

The advantage of placing the warning in _put is that we could identify
the sequence of register writes that trigger the error, so a stack trace
would be more useful i.e. a WARN instead.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre