Re: [PATCH] drm/i915: hold forcewake around ring hw init

[Eugeni Dodonov <eugeni.dodonov@linux.intel.com>]

On 06/04/2012 06:18 AM, Daniel Vetter wrote:
> Empirical evidence suggests that we need to: On at least one ivb
> machine when running the hangman i-g-t test, the rings don't properly
> initialize properly - the RING_START registers seems to be stuck at
> all zeros.
>
> Holding forcewake around this register init sequences makes chip reset
> reliable again. Note that this is not the first such issue:
>
> commit f01db988ef6f6c70a6cc36ee71e4a98a68901229
> Author: Sean Paul<seanpaul@chromium.org>
> Date:   Fri Mar 16 12:43:22 2012 -0400
>
>      drm/i915: Add wait_for in init_ring_common
>
> added delay loops to make RING_START and RING_CTL initialization
> reliable on the blt ring at boot-up. So I guess it won't hurt if we do
> this unconditionally for all force_wake needing gpus.
>
> To avoid copy&pasting of the HAS_FORCE_WAKE check I've added a new
> intel_info bit for that.
>
> v2: Fixup missing commas in static struct and properly handling the
> error case in init_ring_common, both noticed by Jani Nikula.
>
> Cc: stable@vger.kernel.org
> Reported-by: Yang Guang<guang.a.yang@intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50522
> Signed-Off-by: Daniel Vetter<daniel.vetter@ffwll.ch>

The new .has_forcewake looks nice! Just one very tiny bikeshed below :).

Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>

> @@ -285,6 +285,7 @@ struct intel_device_info {
>   	u8 is_ivybridge:1;
>   	u8 is_valleyview:1;
>   	u8 has_pch_split:1;
> +	u8 has_force_wake:1;
>   	u8 is_haswell:1;
>   	u8 has_fbc:1;
>   	u8 has_pipe_cxsr:1;

While you are on it, maybe it would make sense to move is_haswell up, so 
all the 'is_*' and 'has_*' flags would stay together?

It is partly may fault though, due to the has_pch_split which ended up 
in wrong place, but as you are touching those fields anyway, perhaps we 
could rectify it for the future? :)

Eugeni