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    SubjectRe: [PATCHv3 3/8] drm/omap: add support for manually updated displays
    On Fri, Apr 20, 2018 at 10:09:38AM +0300, Tomi Valkeinen wrote:
    > Hi Sebastian,
    >
    > On 30/03/18 20:18, Sebastian Reichel wrote:
    > > This adds the required infrastructure for manually
    > > updated displays, such as DSI command mode panels.
    > >
    > > While those panels often support partial updates
    > > we currently always do a full refresh. Display
    > > will be refreshed when something calls the dirty
    > > callback, such as libdrm's drmModeDirtyFB().
    > >
    > > This is currently being implemented for the kernel
    > > console and for Xorg. Weston currently does not
    > > implement this and is known not to work on manually
    > > updated displays.
    > >
    > > Tested-by: Tony Lindgren <tony@atomide.com>
    > > Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
    > > ---
    > > drivers/gpu/drm/omapdrm/omap_crtc.c | 107 +++++++++++++++++++++++++++++++++---
    > > drivers/gpu/drm/omapdrm/omap_crtc.h | 1 +
    > > drivers/gpu/drm/omapdrm/omap_fb.c | 20 +++++++
    > > 3 files changed, 120 insertions(+), 8 deletions(-)
    > >
    > > diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c b/drivers/gpu/drm/omapdrm/omap_crtc.c
    > > index b893985e4efb..1b91bff5bac6 100644
    > > --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
    > > +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
    > > @@ -51,6 +51,7 @@ struct omap_crtc {
    > > bool pending;
    > > wait_queue_head_t pending_wait;
    > > struct drm_pending_vblank_event *event;
    > > + struct delayed_work update_work;
    > >
    > > void (*framedone_handler)(void *);
    > > void *framedone_handler_data;
    > > @@ -146,6 +147,25 @@ static void omap_crtc_dss_disconnect(struct omap_drm_private *priv,
    > > static void omap_crtc_dss_start_update(struct omap_drm_private *priv,
    > > enum omap_channel channel)
    > > {
    > > + priv->dispc_ops->mgr_enable(priv->dispc, channel, true);
    > > +}
    > > +
    > > +static bool omap_crtc_is_manually_updated(struct drm_crtc *crtc)
    > > +{
    > > + struct drm_connector *connector;
    > > + struct drm_connector_list_iter conn_iter;
    > > + bool result = false;
    > > +
    > > + drm_connector_list_iter_begin(crtc->dev, &conn_iter);
    > > + drm_for_each_connector_iter(connector, &conn_iter) {
    > > + if (connector->state->crtc != crtc)
    > > + continue;
    > > + result = omap_connector_get_manually_updated(connector);
    > > + break;
    > > + }
    > > + drm_connector_list_iter_end(&conn_iter);
    >
    > It would be much nicer if the is-manual flag was somehow conveyed from
    > connector/encoder to the crtc when doing modesetting. I don't know how
    > or where, so just thinking out loud. However, if we need to do such loop
    > as above, I think we should just do it once, perhaps in
    > omap_crtc_atomic_enable, and store the value in omap_crtc's private data.

    Do it in your atomic_check code, and store it as a omap private bit in
    omap_crtc_state. That guarantees you that it's always up-to-date, and will
    never change (except when you get a completely new state).

    Recomputing derived state like this as part of your atomic_commit code
    isn't recommended much.
    -Daniel

    >
    > > +
    > > + return result;
    > > }
    > >
    > > /* Called only from the encoder enable/disable and suspend/resume handlers. */
    > > @@ -157,12 +177,17 @@ static void omap_crtc_set_enabled(struct drm_crtc *crtc, bool enable)
    > > enum omap_channel channel = omap_crtc->channel;
    > > struct omap_irq_wait *wait;
    > > u32 framedone_irq, vsync_irq;
    > > + bool is_manual = omap_crtc_is_manually_updated(crtc);
    > > + enum omap_display_type type = omap_crtc_output[channel]->output_type;
    > > int ret;
    > >
    > > if (WARN_ON(omap_crtc->enabled == enable))
    > > return;
    > >
    > > - if (omap_crtc_output[channel]->output_type == OMAP_DISPLAY_TYPE_HDMI) {
    > > + if (is_manual)
    > > + omap_irq_enable_framedone(crtc, enable);
    > > +
    > > + if (is_manual || type == OMAP_DISPLAY_TYPE_HDMI) {
    > > priv->dispc_ops->mgr_enable(priv->dispc, channel, enable);
    > > omap_crtc->enabled = enable;
    > > return;
    >
    > This doesn't look correct, omap_crtc_dss_start_update() already sets the
    > enable bit for manual update displays. And you don't want to set the
    > enable to false with manual update displays.
    >
    > HDMI handling here is already a special case due to HW issues, so I'd
    > rather see the manual update handled separately from the HDMI.
    >
    > > @@ -214,7 +239,6 @@ static void omap_crtc_set_enabled(struct drm_crtc *crtc, bool enable)
    > > }
    > > }
    > >
    > > -
    > > static int omap_crtc_dss_enable(struct omap_drm_private *priv,
    > > enum omap_channel channel)
    > > {
    > > @@ -378,6 +402,53 @@ void omap_crtc_framedone_irq(struct drm_crtc *crtc, uint32_t irqstatus)
    > > wake_up(&omap_crtc->pending_wait);
    > > }
    > >
    > > +void omap_crtc_flush(struct drm_crtc *crtc)
    > > +{
    > > + struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
    > > +
    > > + if (!omap_crtc_is_manually_updated(crtc))
    > > + return;
    > > +
    > > + if (!delayed_work_pending(&omap_crtc->update_work))
    > > + schedule_delayed_work(&omap_crtc->update_work, 0);
    > > +}
    >
    > Why delayed work here?
    >
    > It's actually not quite clear to me how manual update displays work with
    > DRM...
    >
    > As far as I see, we have essentially two cases: 1) single buffering,
    > where the userspace must set an area in the fb dirty, which then
    > triggers the update, 2) multi buffering, which doesn't need fb dirty,
    > but just a page flip which triggers the update.
    >
    > In the 2) case (which I think is the optimal case which all the modern
    > apps should use), there's no need for delayed work or any work, and the
    > code flow should be very similar to the auto-update model.
    >
    > Also, as Daniel mentioned in "drm/omapdrm: Nuke
    > omap_framebuffer_get_next_connector()" thread, the dirtying mechanism in
    > the series is not valid.
    >
    > Tomi
    >
    > --
    > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
    > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
    > _______________________________________________
    > dri-devel mailing list
    > dri-devel@lists.freedesktop.org
    > https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

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