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SubjectRe: [PATCH 2/2] drm/vkms: Add support for writeback
On Fri, Jun 07, 2019 at 02:17:20PM +0000, Brian Starkey wrote:
> Hi Rodrigo,
>
> On Thu, Jun 06, 2019 at 07:41:01PM -0300, 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.
> >
> > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> > ---
> > drivers/gpu/drm/vkms/Makefile | 9 +-
> > drivers/gpu/drm/vkms/vkms_crtc.c | 5 +
> > drivers/gpu/drm/vkms/vkms_drv.c | 10 ++
> > drivers/gpu/drm/vkms/vkms_drv.h | 12 ++
> > drivers/gpu/drm/vkms/vkms_output.c | 6 +
> > drivers/gpu/drm/vkms/vkms_writeback.c | 165 ++++++++++++++++++++++++++
> > 6 files changed, 206 insertions(+), 1 deletion(-)
> > 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 89f09bec7b23..90eb7acd618d 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_crc.o
> > +vkms-y := \
> > + vkms_drv.o \
> > + vkms_plane.o \
> > + vkms_output.o \
> > + vkms_crtc.o \
> > + vkms_gem.o \
> > + vkms_crc.o \
> > + vkms_writeback.o
> >
> > obj-$(CONFIG_DRM_VKMS) += vkms.o
> > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> > index 1bbe099b7db8..ce797e265b1b 100644
> > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > @@ -23,6 +23,11 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
> > if (!ret)
> > DRM_ERROR("vkms failure on handling vblank");
> >
> > + if (output->writeback_status == WB_START) {
> > + drm_writeback_signal_completion(&output->wb_connector, 0);
> > + output->writeback_status = WB_STOP;
> > + }
> > +
> > if (state && output->crc_enabled) {
> > u64 frame = drm_crtc_accurate_vblank_count(crtc);
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > index 92296bd8f623..d5917d5a45e3 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > @@ -29,6 +29,10 @@ bool enable_cursor;
> > module_param_named(enable_cursor, enable_cursor, bool, 0444);
> > MODULE_PARM_DESC(enable_cursor, "Enable/Disable cursor support");
> >
> > +int enable_writeback;
> > +module_param_named(enable_writeback, enable_writeback, int, 0444);
> > +MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector");
> > +
> > static const struct file_operations vkms_driver_fops = {
> > .owner = THIS_MODULE,
> > .open = drm_open,
> > @@ -123,6 +127,12 @@ static int __init vkms_init(void)
> > goto out_fini;
> > }
> >
> > + vkms_device->output.writeback_status = WB_DISABLED;
> > + if (enable_writeback) {
> > + vkms_device->output.writeback_status = WB_STOP;
> > + DRM_INFO("Writeback connector enabled");
> > + }
> > +
> > ret = vkms_modeset_init(vkms_device);
> > if (ret)
> > goto out_fini;
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index e81073dea154..ca1f9ee63ec8 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -7,6 +7,7 @@
> > #include <drm/drm.h>
> > #include <drm/drm_gem.h>
> > #include <drm/drm_encoder.h>
> > +#include <drm/drm_writeback.h>
> > #include <linux/hrtimer.h>
> >
> > #define XRES_MIN 20
> > @@ -60,14 +61,22 @@ struct vkms_crtc_state {
> > u64 frame_end;
> > };
> >
> > +enum wb_status {
> > + WB_DISABLED,
> > + WB_START,
> > + WB_STOP,
> > +};
> > +
> > 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;
> > bool crc_enabled;
> > + enum wb_status writeback_status;
> > /* ordered wq for crc_work */
> > struct workqueue_struct *crc_workq;
> > /* protects concurrent access to crc_data */
> > @@ -141,4 +150,7 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
> > size_t *values_cnt);
> > void vkms_crc_work_handle(struct work_struct *work);
> >
> > +/* Writeback */
> > +int 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 1442b447c707..1fc1d4e9585c 100644
> > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > @@ -91,6 +91,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > goto err_attach;
> > }
> >
> > + if (vkmsdev->output.writeback_status != WB_DISABLED) {
> > + ret = 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..f7b962ae5646
> > --- /dev/null
> > +++ b/drivers/gpu/drm/vkms/vkms_writeback.c
> > @@ -0,0 +1,165 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +
> > +#include "vkms_drv.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 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 != DRM_FORMAT_XRGB8888) {
> > + 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;
> > +
> > + if (!job->fb)
> > + return;
> > +
> > + gem_obj = drm_gem_fb_get_obj(job->fb, 0);
> > + vkms_gem_vunmap(gem_obj);
> > +}
> > +
> > +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;
> > + void *priv_data = conn_state->writeback_job->priv;
> > + struct vkms_crc_data *primary_data = NULL;
> > + struct drm_framebuffer *fb = NULL;
> > + struct vkms_gem_object *vkms_obj;
> > + struct drm_gem_object *gem_obj;
> > + struct drm_plane *plane;
> > +
> > + if (!conn_state)
> > + return;
> > +
> > + if (!conn_state->writeback_job || !conn_state->writeback_job->fb) {
> > + output->writeback_status = WB_STOP;
> > + DRM_DEBUG_DRIVER("Disable writeback\n");
> > + return;
> > + }
> > +
> > + drm_for_each_plane(plane, &vkmsdev->drm) {
> > + struct vkms_plane_state *vplane_state;
> > + struct vkms_crc_data *plane_data;
> > +
> > + vplane_state = to_vkms_plane_state(plane->state);
> > + plane_data = vplane_state->crc_data;
> > +
> > + if (drm_framebuffer_read_refcount(&plane_data->fb) == 0)
> > + continue;
> It's not really specific to this patch, but this looks kinda
> weird to me. You've got a copy of the fb struct in plane_data?
>
> It seems like that would break a bunch of refcounting if nothing else.
>
> Can't you use plane->state->fb directly, and just check if it's NULL?

It's complicated, and I'm working on some patches to fix that.
Prep/infrastructure work is now on the mailing list.
-Daniel

>
> > +
> > + if (plane->type == DRM_PLANE_TYPE_PRIMARY)
> > + primary_data = plane_data;
> > + }
> > +
> > + if (!primary_data)
> > + return;
> > +
> > + fb = &primary_data->fb;
> > + gem_obj = drm_gem_fb_get_obj(fb, 0);
> > + vkms_obj = drm_gem_to_vkms_gem(gem_obj);
> > +
> > + if (!vkms_obj->vaddr || !priv_data)
> > + return;
> > +
> > + memcpy(priv_data, vkms_obj->vaddr, vkms_obj->gem.size);
> > + drm_writeback_queue_job(wb_conn, state);
> > + output->writeback_status = WB_START;
>
> You probably don't need the deferred completion signaling. I'd expect
> this to work OK (and it matches the API semantics):
>
> drm_writeback_queue_job(wb_conn, state);
> memcpy(priv_data, vkms_obj->vaddr, vkms_obj->gem.size);
> drm_writeback_signal_completion(wb_conn, 0);
>
>
> Cheers,
> -Brian
>
> > +}
> > +
> > +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 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_formats,
> > + ARRAY_SIZE(vkms_formats));
> > +}
> > +
> > --
> > 2.21.0
>
>

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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