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From: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Haneen Mohammed <hamohammed.sa@gmail.com>
Subject: Re: [PATCH 09/10] drm/vkms: totally reworked crc data tracking
Date: Wed, 12 Jun 2019 10:46:28 -0300	[thread overview]
Message-ID: <CADKXj+7UK0Y=6rOb2hNW380mNCfjojsWTPcpEhuKEybxvw_rTQ@mail.gmail.com> (raw)
In-Reply-To: <20190606222751.32567-10-daniel.vetter@ffwll.ch>

On Thu, Jun 6, 2019 at 7:28 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> The crc computation worker needs to be able to get at some data
> structures and framebuffer mappings, while potentially more atomic
> updates are going on. The solution thus far is to copy relevant bits
> around, but that's very tedious.
>
> Here's a new approach, which tries to be more clever, but relies on a
> few not-so-obvious things:
> - crtc_state is always updated when a plane_state changes. Therefore
>   we can just stuff plane_state pointers into a crtc_state. That
>   solves the problem of easily getting at the needed plane_states.

Just for curiosity, where exactly the crct_state is updated? If
possible, could you elaborate a little bit about this?

> - with the flushing changes from previous patches the above also holds
>   without races due to the next atomic update being a bit eager with
>   cleaning up pending work - we always wait for all crc work items to
>   complete before unmapping framebuffers.
> - we also need to make sure that the hrtimer fires off the right
>   worker. Keep a new distinct crc_state pointer, under the
>   vkms_output->lock protection for this. Note that crtc->state is
>   updated very early in the atomic commit, way before we arm the
>   vblank event - the vblank event should always match the buffers we
>   use to compute the crc. This also solves an issue in the hrtimer,
>   where we've accessed drm_crtc->state without holding the right locks
>   (we held none - oops).
> - in the worker itself we can then just access the plane states we
>   need, again solving a bunch of ordering and locking issues.
>   Accessing plane->state requires locks, accessing the private
>   vkms_crtc_state->active_planes pointer only requires that the memory
>   doesn't get freed too early.
>
> The idea behind vkms_crtc_state->active_planes is that this would
> contain all visible planes, in z-order, as a first step towards a more
> generic blending implementation.
>
> Note that this patch also fixes races between prepare_fb/cleanup_fb
> and the crc worker accessing ->vaddr.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
>  drivers/gpu/drm/vkms/vkms_crc.c  | 21 +++--------
>  drivers/gpu/drm/vkms/vkms_crtc.c | 60 +++++++++++++++++++++++++++++---
>  drivers/gpu/drm/vkms/vkms_drv.h  |  9 ++++-
>  3 files changed, 67 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c
> index 9d15e5e85830..0d31cfc32042 100644
> --- a/drivers/gpu/drm/vkms/vkms_crc.c
> +++ b/drivers/gpu/drm/vkms/vkms_crc.c
> @@ -159,11 +159,8 @@ void vkms_crc_work_handle(struct work_struct *work)
>                                                 crc_work);
>         struct drm_crtc *crtc = crtc_state->base.crtc;
>         struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> -       struct vkms_device *vdev = container_of(out, struct vkms_device,
> -                                               output);
>         struct vkms_crc_data *primary_crc = NULL;
>         struct vkms_crc_data *cursor_crc = NULL;
> -       struct drm_plane *plane;
>         u32 crc32 = 0;
>         u64 frame_start, frame_end;
>         bool crc_pending;
> @@ -184,21 +181,11 @@ void vkms_crc_work_handle(struct work_struct *work)
>         if (!crc_pending)
>                 return;
>
> -       drm_for_each_plane(plane, &vdev->drm) {
> -               struct vkms_plane_state *vplane_state;
> -               struct vkms_crc_data *crc_data;
> +       if (crtc_state->num_active_planes >= 1)
> +               primary_crc = crtc_state->active_planes[0]->crc_data;
>
> -               vplane_state = to_vkms_plane_state(plane->state);
> -               crc_data = vplane_state->crc_data;
> -
> -               if (drm_framebuffer_read_refcount(&crc_data->fb) == 0)
> -                       continue;
> -
> -               if (plane->type == DRM_PLANE_TYPE_PRIMARY)
> -                       primary_crc = crc_data;
> -               else
> -                       cursor_crc = crc_data;
> -       }
> +       if (crtc_state->num_active_planes == 2)
> +               cursor_crc = crtc_state->active_planes[1]->crc_data;
>
>         if (primary_crc)
>                 crc32 = _vkms_get_crc(primary_crc, cursor_crc);
> diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> index 48a793ba4030..14156ed70415 100644
> --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0+
>
>  #include "vkms_drv.h"
> +#include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_probe_helper.h>
>
> @@ -9,7 +10,7 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
>         struct vkms_output *output = container_of(timer, struct vkms_output,
>                                                   vblank_hrtimer);
>         struct drm_crtc *crtc = &output->crtc;
> -       struct vkms_crtc_state *state = to_vkms_crtc_state(crtc->state);
> +       struct vkms_crtc_state *state;
>         u64 ret_overrun;
>         bool ret;
>
> @@ -23,6 +24,7 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
>         if (!ret)
>                 DRM_ERROR("vkms failure on handling vblank");
>
> +       state = output->crc_state;
>         if (state && output->crc_enabled) {
>                 u64 frame = drm_crtc_accurate_vblank_count(crtc);
>
> @@ -124,10 +126,9 @@ static void vkms_atomic_crtc_destroy_state(struct drm_crtc *crtc,
>
>         __drm_atomic_helper_crtc_destroy_state(state);
>
> -       if (vkms_state) {
> -               WARN_ON(work_pending(&vkms_state->crc_work));
> -               kfree(vkms_state);
> -       }
> +       WARN_ON(work_pending(&vkms_state->crc_work));
> +       kfree(vkms_state->active_planes);
> +       kfree(vkms_state);
>  }
>
>  static void vkms_atomic_crtc_reset(struct drm_crtc *crtc)
> @@ -156,6 +157,52 @@ static const struct drm_crtc_funcs vkms_crtc_funcs = {
>         .verify_crc_source      = vkms_verify_crc_source,
>  };
>
> +static int vkms_crtc_atomic_check(struct drm_crtc *crtc,
> +                                  struct drm_crtc_state *state)
> +{
> +       struct vkms_crtc_state *vkms_state = to_vkms_crtc_state(state);
> +       struct drm_plane *plane;
> +       struct drm_plane_state *plane_state;
> +       int i = 0, ret;
> +
> +       if (vkms_state->active_planes)
> +               return 0;
> +
> +       ret = drm_atomic_add_affected_planes(state->state, crtc);
> +       if (ret < 0)
> +               return ret;
> +
> +       drm_for_each_plane_mask(plane, crtc->dev, state->plane_mask) {

In the drm_for_each_plane_mask documentation says: “ Iterate over all
planes specified by bitmask”. I did not understand what it means by
“specified by bitmask” and the use of this macro in this context. I
tried to replace it for drm_for_each_plane, but the test just break.
Could you explain a little bit the magic behind
drm_for_each_plane_mask?

> +               plane_state = drm_atomic_get_existing_plane_state(state->state,
> +                                                                 plane);
> +               WARN_ON(!plane_state);
> +
> +               if (!plane_state->visible)
> +                       continue;
> +
> +               i++;
> +       }
> +
> +       vkms_state->active_planes = kcalloc(i, sizeof(plane), GFP_KERNEL);
> +       if (!vkms_state->active_planes)
> +               return -ENOMEM;
> +       vkms_state->num_active_planes = i;
> +
> +       i = 0;
> +       drm_for_each_plane_mask(plane, crtc->dev, state->plane_mask) {
> +               plane_state = drm_atomic_get_existing_plane_state(state->state,
> +                                                                 plane);
> +
> +               if (!plane_state->visible)
> +                       continue;
> +
> +               vkms_state->active_planes[i++] =
> +                       to_vkms_plane_state(plane_state);
> +       }
> +
> +       return 0;
> +}
> +
>  static void vkms_crtc_atomic_enable(struct drm_crtc *crtc,
>                                     struct drm_crtc_state *old_state)
>  {
> @@ -197,10 +244,13 @@ static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
>                 crtc->state->event = NULL;
>         }
>
> +       vkms_output->crc_state = to_vkms_crtc_state(crtc->state);
> +
>         spin_unlock_irq(&vkms_output->lock);
>  }
>
>  static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
> +       .atomic_check   = vkms_crtc_atomic_check,
>         .atomic_begin   = vkms_crtc_atomic_begin,
>         .atomic_flush   = vkms_crtc_atomic_flush,
>         .atomic_enable  = vkms_crtc_atomic_enable,
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index 2a35299bfb89..4e7450111d45 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -49,6 +49,10 @@ struct vkms_crtc_state {
>         struct drm_crtc_state base;
>         struct work_struct crc_work;
>
> +       int num_active_planes;
> +       /* stack of active planes for crc computation, should be in z order */
> +       struct vkms_plane_state **active_planes;
> +
>         /* below three are protected by vkms_output.crc_lock */
>         bool crc_pending;
>         u64 frame_start;
> @@ -62,12 +66,15 @@ struct vkms_output {
>         struct hrtimer vblank_hrtimer;
>         ktime_t period_ns;
>         struct drm_pending_vblank_event *event;
> -       bool crc_enabled;
>         /* ordered wq for crc_work */
>         struct workqueue_struct *crc_workq;
>         /* protects concurrent access to crc_data */
>         spinlock_t lock;
>
> +       /* protected by @lock */
> +       bool crc_enabled;
> +       struct vkms_crtc_state *crc_state;
> +
>         spinlock_t crc_lock;
>  };
>
> --
> 2.20.1
>


-- 

Rodrigo Siqueira
https://siqueira.tech
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  reply	other threads:[~2019-06-12 13:46 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-06 22:27 [PATCH 00/10] drm/vkms: rework crc worker Daniel Vetter
2019-06-06 22:27 ` [PATCH 01/10] drm/vkms: Fix crc worker races Daniel Vetter
2019-06-12 13:33   ` Rodrigo Siqueira
2019-06-12 14:48     ` Daniel Vetter
2019-06-18  2:39       ` Rodrigo Siqueira
2019-06-18  8:49         ` Daniel Vetter
2019-06-06 22:27 ` [PATCH 02/10] drm/vkms: Use spin_lock_irq in process context Daniel Vetter
2019-06-12 13:34   ` Rodrigo Siqueira
2019-06-12 14:54     ` Daniel Vetter
2019-06-06 22:27 ` [PATCH 03/10] drm/vkms: Rename vkms_output.state_lock to crc_lock Daniel Vetter
2019-06-12 13:38   ` Rodrigo Siqueira
2019-06-13  7:48     ` Daniel Vetter
2019-06-06 22:27 ` [PATCH 04/10] drm/vkms: Move format arrays to vkms_plane.c Daniel Vetter
2019-06-12 13:39   ` Rodrigo Siqueira
2019-06-19  2:12   ` Rodrigo Siqueira
2019-06-06 22:27 ` [PATCH 05/10] drm/vkms: Add our own commit_tail Daniel Vetter
2019-06-06 22:27 ` [PATCH 06/10] drm/vkms: flush crc workers earlier in commit flow Daniel Vetter
2019-06-12 13:42   ` Rodrigo Siqueira
2019-06-13  7:53     ` Daniel Vetter
2019-06-13  7:55       ` Daniel Vetter
2019-06-18  2:31       ` Rodrigo Siqueira
2019-06-06 22:27 ` [PATCH 07/10] drm/vkms: Dont flush crc worker when we change crc status Daniel Vetter
2019-06-19  2:17   ` Rodrigo Siqueira
2019-06-19  7:47     ` Daniel Vetter
2019-06-06 22:27 ` [PATCH 08/10] drm/vkms: No _irqsave within spin_lock_irq needed Daniel Vetter
2019-06-12 13:43   ` Rodrigo Siqueira
2019-06-06 22:27 ` [PATCH 09/10] drm/vkms: totally reworked crc data tracking Daniel Vetter
2019-06-12 13:46   ` Rodrigo Siqueira [this message]
2019-06-13  7:59     ` Daniel Vetter
2019-06-06 22:27 ` [PATCH 10/10] drm/vkms: No need for ->pages_lock in crc work anymore Daniel Vetter
2019-06-12 13:47   ` Rodrigo Siqueira
2019-06-12 13:28 ` [PATCH 00/10] drm/vkms: rework crc worker Rodrigo Siqueira
2019-06-12 14:42   ` Daniel Vetter
2019-06-18  2:49     ` Rodrigo Siqueira
2019-06-18  8:56       ` Daniel Vetter
2019-06-18 21:54         ` Rodrigo Siqueira
2019-06-18 22:06           ` Daniel Vetter
2019-06-18 22:07             ` Daniel Vetter
2019-06-18 22:25               ` Rodrigo Siqueira
2019-06-18 22:39                 ` Daniel Vetter
2019-06-26  1:44             ` Rodrigo Siqueira
2019-06-26  7:54               ` Daniel Vetter
2019-06-26 13:46                 ` Rodrigo Siqueira
2019-07-01  3:30                 ` Rodrigo Siqueira

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