[Intel-gfx] 830GM still woes

[Chris Wilson]

On Fri, May 16, 2014 at 04:02:48PM +0200, Thomas Richter wrote:
> It's not that I haven't had a patch for it. Really trivial. I wonder
> what keeps you from adding this to the kernel and just make things
> working?

You mean this patch?

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index f671aca..3981898 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -944,7 +944,7 @@ static const struct intel_watermark_params i915_wm_info = {
 static const struct intel_watermark_params i830_wm_info = {
        I855GM_FIFO_SIZE,
        I915_MAX_WM,
-       1,
+       8,
        2,
        I830_FIFO_LINE_SIZE
 };
@@ -1001,7 +1001,7 @@ static unsigned long intel_calculate_wm(unsigned long clock_in_khz,
        /* Don't promote wm_size to unsigned... */
        if (wm_size > (long)wm->max_wm)
                wm_size = wm->max_wm;
-       if (wm_size <= 0)
+       if (wm_size < (long)wm->default_wm)
                wm_size = wm->default_wm;
        return wm_size;
 }

I haven't spotted any explanation as to why that is, but a rough guess
would be that we program it to read in blocks of 8 superwords and that
it tries and fails to read from memory when the fifo only has room for 1
superword.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre