Re: [Intel-gfx] [PATCH 4/9] drm/i915/ddi: Track power reference taken for encoder DDI IO use

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Imre Deak <imre.deak@intel.com>, intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 4/9] drm/i915/ddi: Track power reference taken for encoder DDI IO use
Date: Mon, 30 Nov 2020 22:00:33 +0000	[thread overview]
Message-ID: <160677363371.12351.7483170084025008582@build.alporthouse.com> (raw)
In-Reply-To: <20201130212200.2811939-5-imre.deak@intel.com>

Quoting Imre Deak (2020-11-30 21:21:55)
> Add wakeref tracking for the DDI encoders' DDI_IO display power domain
> references.
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c      | 38 ++++++++++++-------
>  .../drm/i915/display/intel_display_types.h    |  1 +
>  2 files changed, 25 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 92940a0c5ef8..9518d298b0f7 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -2285,9 +2285,11 @@ static void intel_ddi_get_power_domains(struct intel_encoder *encoder,
>         dig_port = enc_to_dig_port(encoder);
>  
>         if (!intel_phy_is_tc(dev_priv, phy) ||
> -           dig_port->tc_mode != TC_PORT_TBT_ALT)
> -               intel_display_power_get(dev_priv,
> -                                       dig_port->ddi_io_power_domain);
> +           dig_port->tc_mode != TC_PORT_TBT_ALT) {
> +               drm_WARN_ON(&dev_priv->drm, dig_port->ddi_io_wakeref);
> +               dig_port->ddi_io_wakeref = intel_display_power_get(dev_priv,
> +                                                                  dig_port->ddi_io_power_domain);
> +       }

> @@ -3958,8 +3967,9 @@ static void intel_ddi_post_disable_hdmi(struct intel_atomic_state *state,
>  
>         intel_disable_ddi_buf(encoder, old_crtc_state);
>  
> -       intel_display_power_put_unchecked(dev_priv,
> -                                         dig_port->ddi_io_power_domain);
> +       intel_display_power_put(dev_priv,
> +                               dig_port->ddi_io_power_domain,
> +                               fetch_and_zero(&dig_port->ddi_io_wakeref));

I remember that once we had trouble with this being a macro and not
evaluating the fetch_and_zero() when used as an argument.

Looks like we still have the same trouble with

#if !IS_ENABLED(CONFIG_DRM_I915_DEBUG_RUNTIME_PM)
static inline void
intel_display_power_put(struct drm_i915_private *i915,
                        enum intel_display_power_domain domain,
                        intel_wakeref_t wakeref)
{
        intel_display_power_put_unchecked(i915, domain);
}
#endif

will cause the ddi_io_wakeref to not be cleared, and the warn on to be
hit in non-debug builds.
-Chris
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