Re: [PATCH v5 3/3] drm/vkms: Add support for writeback

[Melissa Wen]

On Tue, Aug 25, 2020 at 12:45 PM Melissa Wen <melissa.srw@xxxxxxxxx> wrote:
>
> On 08/24, Rodrigo Siqueira wrote:
> > This patch implements the necessary functions to add writeback support
> > for vkms. This feature is useful for testing compositors if you don't
> > have hardware with writeback support.
> >
> > Change in V4 (Emil and Melissa):
> > - Move signal completion above drm_crtc_add_crc_entry()
> > - Make writeback always available
> > - Use appropriate namespace
> > - Drop fb check in vkms_wb_atomic_commit
> > - Make vkms_set_composer visible for writeback code
> > - Enable composer operation on prepare_job and disable it on cleanup_job
> >
> > Change in V3 (Daniel):
> > - If writeback is enabled, compose everything into the writeback buffer
> > instead of CRC private buffer
> > - Guarantees that the CRC will match exactly what we have in the
> > writeback buffer.
> >
> > Change in V2:
> > - Rework signal completion (Brian)
> > - Integrates writeback with active_planes (Daniel)
> > - Compose cursor (Daniel)
> >
> > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
> > ---
> >  drivers/gpu/drm/vkms/Makefile         |   9 +-
> >  drivers/gpu/drm/vkms/vkms_composer.c  |  21 +++-
> >  drivers/gpu/drm/vkms/vkms_drv.h       |  11 +-
> >  drivers/gpu/drm/vkms/vkms_output.c    |   4 +
> >  drivers/gpu/drm/vkms/vkms_writeback.c | 143 ++++++++++++++++++++++++++
> >  5 files changed, 181 insertions(+), 7 deletions(-)
> >  create mode 100644 drivers/gpu/drm/vkms/vkms_writeback.c
> >
> > diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> > index 0b767d7efa24..333d3cead0e3 100644
> > --- a/drivers/gpu/drm/vkms/Makefile
> > +++ b/drivers/gpu/drm/vkms/Makefile
> > @@ -1,4 +1,11 @@
> >  # SPDX-License-Identifier: GPL-2.0-only
> > -vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_composer.o
> > +vkms-y := \
> > +     vkms_drv.o \
> > +     vkms_plane.o \
> > +     vkms_output.o \
> > +     vkms_crtc.o \
> > +     vkms_gem.o \
> > +     vkms_composer.o \
> > +     vkms_writeback.o
> >
> >  obj-$(CONFIG_DRM_VKMS) += vkms.o
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index 387b0690a64a..656085c4ebf3 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -163,16 +163,17 @@ void vkms_composer_worker(struct work_struct *work)
> >       struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> >       struct vkms_composer *primary_composer = NULL;
> >       struct vkms_composer *cursor_composer = NULL;
> > +     bool crc_pending, wb_pending;
> >       void *vaddr_out = NULL;
> >       u32 crc32 = 0;
> >       u64 frame_start, frame_end;
> > -     bool crc_pending;
> >       int ret;
> >
> >       spin_lock_irq(&out->composer_lock);
> >       frame_start = crtc_state->frame_start;
> >       frame_end = crtc_state->frame_end;
> >       crc_pending = crtc_state->crc_pending;
> > +     wb_pending = crtc_state->wb_pending;
> >       crtc_state->frame_start = 0;
> >       crtc_state->frame_end = 0;
> >       crtc_state->crc_pending = false;
> > @@ -194,22 +195,32 @@ void vkms_composer_worker(struct work_struct *work)
> >       if (!primary_composer)
> >               return;
> >
> > +     if (wb_pending)
> > +             vaddr_out = crtc_state->active_writeback;
> > +
> >       ret = compose_planes(&vaddr_out, primary_composer, cursor_composer);
> >       if (ret) {
> > -             if (ret == -EINVAL)
> > +             if (ret == -EINVAL && !wb_pending)
> >                       kfree(vaddr_out);
> >               return;
> >       }
> >
> >       crc32 = compute_crc(vaddr_out, primary_composer);
> >
> > +     if (wb_pending) {
> > +             drm_writeback_signal_completion(&out->wb_connector, 0);
> > +             spin_lock_irq(&out->composer_lock);
> > +             crtc_state->wb_pending = false;
> > +             spin_unlock_irq(&out->composer_lock);
> > +     } else {
> > +             kfree(vaddr_out);
> > +     }
> > +
> >       /*
> >        * The worker can fall behind the vblank hrtimer, make sure we catch up.
> >        */
> >       while (frame_start <= frame_end)
> >               drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
> > -
> > -     kfree(vaddr_out);
> >  }
> >
> >  static const char * const pipe_crc_sources[] = {"auto"};
> > @@ -252,7 +263,7 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
> >       return 0;
> >  }
> >
> > -static void vkms_set_composer(struct vkms_output *out, bool enabled)
> > +void vkms_set_composer(struct vkms_output *out, bool enabled)
> >  {
> >       bool old_enabled;
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index f4036bb0b9a8..641d8bc52a3a 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -8,6 +8,7 @@
> >  #include <drm/drm.h>
> >  #include <drm/drm_gem.h>
> >  #include <drm/drm_encoder.h>
> > +#include <drm/drm_writeback.h>
> >
> >  #define XRES_MIN    20
> >  #define YRES_MIN    20
> > @@ -19,6 +20,7 @@
> >  #define YRES_MAX  8192
> >
> >  extern bool enable_cursor;
> > +extern bool enable_writeback;
> >
> >  struct vkms_composer {
> >       struct drm_framebuffer fb;
> > @@ -52,9 +54,11 @@ struct vkms_crtc_state {
> >       int num_active_planes;
> >       /* stack of active planes for crc computation, should be in z order */
> >       struct vkms_plane_state **active_planes;
> > +     void *active_writeback;
> >
> > -     /* below three are protected by vkms_output.composer_lock */
> > +     /* below four are protected by vkms_output.composer_lock */
> >       bool crc_pending;
> > +     bool wb_pending;
> >       u64 frame_start;
> >       u64 frame_end;
> >  };
> > @@ -63,6 +67,7 @@ struct vkms_output {
> >       struct drm_crtc crtc;
> >       struct drm_encoder encoder;
> >       struct drm_connector connector;
> > +     struct drm_writeback_connector wb_connector;
> >       struct hrtimer vblank_hrtimer;
> >       ktime_t period_ns;
> >       struct drm_pending_vblank_event *event;
> > @@ -143,5 +148,9 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
> >
> >  /* Composer Support */
> >  void vkms_composer_worker(struct work_struct *work);
> > +void vkms_set_composer(struct vkms_output *out, bool enabled);
> > +
> > +/* Writeback */
> > +int vkms_enable_writeback_connector(struct vkms_device *vkmsdev);
> >
> >  #endif /* _VKMS_DRV_H_ */
> > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > index 85afb77e97f0..4a1848b0318f 100644
> > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > @@ -80,6 +80,10 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> >               goto err_attach;
> >       }
> >
> > +     ret = vkms_enable_writeback_connector(vkmsdev);
> > +     if (ret)
> > +             DRM_ERROR("Failed to init writeback connector\n");
> > +
> >       drm_mode_config_reset(dev);
> >
> >       return 0;
> > diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c
> > new file mode 100644
> > index 000000000000..ddcd5ad0d7aa
> > --- /dev/null
> > +++ b/drivers/gpu/drm/vkms/vkms_writeback.c
> > @@ -0,0 +1,143 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +
> > +#include "vkms_drv.h"
> > +#include <drm/drm_fourcc.h>
> > +#include <drm/drm_writeback.h>
> > +#include <drm/drm_probe_helper.h>
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_gem_framebuffer_helper.h>
> > +
> > +static const u32 vkms_wb_formats[] = {
> > +     DRM_FORMAT_XRGB8888,
> > +};
> > +
> > +static const struct drm_connector_funcs vkms_wb_connector_funcs = {
> > +     .fill_modes = drm_helper_probe_single_connector_modes,
> > +     .destroy = drm_connector_cleanup,
> > +     .reset = drm_atomic_helper_connector_reset,
> > +     .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> > +     .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > +};
> > +
> > +static int vkms_wb_encoder_atomic_check(struct drm_encoder *encoder,
> > +                                     struct drm_crtc_state *crtc_state,
> > +                                     struct drm_connector_state *conn_state)
> > +{
> > +     struct drm_framebuffer *fb;
> > +     const struct drm_display_mode *mode = &crtc_state->mode;
> > +
> > +     if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
> > +             return 0;
> > +
> > +     fb = conn_state->writeback_job->fb;
> > +     if (fb->width != mode->hdisplay || fb->height != mode->vdisplay) {
> > +             DRM_DEBUG_KMS("Invalid framebuffer size %ux%u\n",
> > +                           fb->width, fb->height);
> > +             return -EINVAL;
> > +     }
> > +
> > +     if (fb->format->format != vkms_wb_formats[0]) {
> > +             struct drm_format_name_buf format_name;
> > +
> > +             DRM_DEBUG_KMS("Invalid pixel format %s\n",
> > +                           drm_get_format_name(fb->format->format,
> > +                                               &format_name));
> > +             return -EINVAL;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct drm_encoder_helper_funcs vkms_wb_encoder_helper_funcs = {
> > +     .atomic_check = vkms_wb_encoder_atomic_check,
> > +};
> > +
> > +static int vkms_wb_connector_get_modes(struct drm_connector *connector)
> > +{
> > +     struct drm_device *dev = connector->dev;
> > +
> > +     return drm_add_modes_noedid(connector, dev->mode_config.max_width,
> > +                                 dev->mode_config.max_height);
> > +}
> > +
> > +static int vkms_wb_prepare_job(struct drm_writeback_connector *wb_connector,
> > +                            struct drm_writeback_job *job)
> > +{
> > +     struct vkms_gem_object *vkms_obj;
> > +     struct drm_gem_object *gem_obj;
> > +     int ret;
> > +
> > +     if (!job->fb)
> > +             return 0;
> > +
> > +     gem_obj = drm_gem_fb_get_obj(job->fb, 0);
> > +     ret = vkms_gem_vmap(gem_obj);
> > +     if (ret) {
> > +             DRM_ERROR("vmap failed: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     vkms_obj = drm_gem_to_vkms_gem(gem_obj);
> > +     job->priv = vkms_obj->vaddr;
> > +
> > +     return 0;
> > +}
> > +
> > +static void vkms_wb_cleanup_job(struct drm_writeback_connector *connector,
> > +                             struct drm_writeback_job *job)
> > +{
> > +     struct drm_gem_object *gem_obj;
> > +     struct vkms_device *vkmsdev;
> > +
> > +     if (!job->fb)
> > +             return;
> > +
> > +     gem_obj = drm_gem_fb_get_obj(job->fb, 0);
> > +     vkms_gem_vunmap(gem_obj);
> > +
> > +     vkmsdev = drm_device_to_vkms_device(gem_obj->dev);
> > +     vkms_set_composer(&vkmsdev->output, false);
> > +}
> > +
> > +static void vkms_wb_atomic_commit(struct drm_connector *conn,
> > +                               struct drm_connector_state *state)
> > +{
> > +     struct vkms_device *vkmsdev = drm_device_to_vkms_device(conn->dev);
> > +     struct vkms_output *output = &vkmsdev->output;
> > +     struct drm_writeback_connector *wb_conn = &output->wb_connector;
> > +     struct drm_connector_state *conn_state = wb_conn->base.state;
> > +     struct vkms_crtc_state *crtc_state = output->composer_state;
> > +
> > +     if (!conn_state)
> > +             return;
> > +
> > +     vkms_set_composer(&vkmsdev->output, true);
> > +
> > +     spin_lock_irq(&output->composer_lock);
> > +     crtc_state->active_writeback = conn_state->writeback_job->priv;
> > +     crtc_state->wb_pending = true;
> > +     spin_unlock_irq(&output->composer_lock);
> > +     drm_writeback_queue_job(wb_conn, state);
> > +}
> > +
> > +static const struct drm_connector_helper_funcs vkms_wb_conn_helper_funcs = {
> > +     .get_modes = vkms_wb_connector_get_modes,
> > +     .prepare_writeback_job = vkms_wb_prepare_job,
> > +     .cleanup_writeback_job = vkms_wb_cleanup_job,
> > +     .atomic_commit = vkms_wb_atomic_commit,
> > +};
> > +
> > +int vkms_enable_writeback_connector(struct vkms_device *vkmsdev)
> > +{
> > +     struct drm_writeback_connector *wb = &vkmsdev->output.wb_connector;
> > +
> > +     vkmsdev->output.wb_connector.encoder.possible_crtcs = 1;
> > +     drm_connector_helper_add(&wb->base, &vkms_wb_conn_helper_funcs);
> > +
> > +     return drm_writeback_connector_init(&vkmsdev->drm, wb,
> > +                                         &vkms_wb_connector_funcs,
> > +                                         &vkms_wb_encoder_helper_funcs,
> > +                                         vkms_wb_formats,
> > +                                         ARRAY_SIZE(vkms_wb_formats));
> > +}
> > +
> Another small fix: there is an extra line above.
> > --
> > 2.28.0
> >
Tested-by: Melissa Wen <melissa.srw@xxxxxxxxx>