linux-kernel - Re: [PATCH v3] drm/vc4: Add a debugfs entry to disable/enable the load tracker

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Date:   Tue, 11 Dec 2018 14:12:33 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3] drm/vc4: Add a debugfs entry to disable/enable the
 load tracker

On Fri,  7 Dec 2018 14:47:57 +0100
Paul Kocialkowski <paul.kocialkowski@...tlin.com> wrote:


> diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
> index f3fd34faa812..e80b1ad5c938 100644
> --- a/drivers/gpu/drm/vc4/vc4_kms.c
> +++ b/drivers/gpu/drm/vc4/vc4_kms.c
> @@ -479,6 +479,7 @@ static const struct drm_private_state_funcs vc4_load_tracker_state_funcs = {
>  static int
>  vc4_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
>  {
> +	struct vc4_dev *vc4 = to_vc4_dev(dev);
>  	int ret;
>  
>  	ret = vc4_ctm_atomic_check(dev, state);
> @@ -489,7 +490,10 @@ vc4_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
>  	if (ret)
>  		return ret;
>  
> -	return vc4_load_tracker_atomic_check(state);
> +	if (vc4->load_tracker_enabled)
> +		return vc4_load_tracker_atomic_check(state);

Even if we don't return an error when ->load_tracker_enabled is false,
we should keep updating the ->{hvs,membus}_load state, otherwise those
fields will contain bad values if we activate the load tracker after
the planes have been enabled.

I suggest moving this test in vc4_load_tracker_atomic_check() just
before

	if (load_state->membus_load > SZ_1G + SZ_512M)