On Mon, Jan 20, 2020 at 01:20:49PM +0100, Thomas Zimmermann wrote:
> At the end of a commit, atomic helpers can generate a VBLANK event
> automatically. Originally implemented for writeback connectors, the
> functionality can be used by any driver and/or hardware without proper
> VBLANK interrupt.
>
> First of all, the patch updates the documentation to make this behaviour
> official: settings struct drm_crtc_state.no_vblank to true enables
> automatic VBLANK generation.
>
> Atomic modesetting helper set the initial value of no_vblank in
> drm_atomic_helper_check_modeset(). If vblanking has been initialized
> for a CRTC, no_blank is disabled. Otherwise it's enabled. Hence,
> atomic helpers will automatically send out VBLANK events with any
> driver that did not initialize vblanking.
>
> As drivers previously send out VBLANK events by themselves, all
> affected drivers have to be updated as well. Usually, deleting the
> driver's vblanking code is sufficient. Xen implements its own logic
> for generating events and therefore needs to override no_vblank
> with a value of false.
>
> v3:
> * squash all related changes patches into this patch
Hm, since the fall-back only happens when the driver hasn't sent out the
even I think it'd be safe to split the driver cleanups into a separate
patch. Makes the core/helper changes stand out more properly.
Even the xen hunk I think isn't strictly needed, since that pick up the
event correctly and clears state->event to NULL.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
> drivers/gpu/drm/arc/arcpgu_crtc.c | 16 --------------
> drivers/gpu/drm/bochs/bochs_kms.c | 9 --------
> drivers/gpu/drm/cirrus/cirrus.c | 8 -------
> drivers/gpu/drm/drm_atomic_helper.c | 10 ++++++++-
> drivers/gpu/drm/drm_mipi_dbi.c | 9 --------
> drivers/gpu/drm/drm_vblank.c | 9 ++++++++
> drivers/gpu/drm/qxl/qxl_display.c | 14 ------------
> drivers/gpu/drm/tiny/gm12u320.c | 9 --------
> drivers/gpu/drm/tiny/ili9225.c | 9 --------
> drivers/gpu/drm/tiny/repaper.c | 9 --------
> drivers/gpu/drm/tiny/st7586.c | 9 --------
> drivers/gpu/drm/vboxvideo/vbox_mode.c | 12 -----------
> drivers/gpu/drm/virtio/virtgpu_display.c | 8 -------
> drivers/gpu/drm/xen/xen_drm_front_kms.c | 13 ++++++++++++
> include/drm/drm_crtc.h | 27 ++++++++++++++++++------
> include/drm/drm_simple_kms_helper.h | 7 ++++--
> 16 files changed, 56 insertions(+), 122 deletions(-)
>
> diff --git a/drivers/gpu/drm/arc/arcpgu_crtc.c b/drivers/gpu/drm/arc/arcpgu_crtc.c
> index 8ae1e1f97a73..be7c29cec318 100644
> --- a/drivers/gpu/drm/arc/arcpgu_crtc.c
> +++ b/drivers/gpu/drm/arc/arcpgu_crtc.c
> @@ -9,7 +9,6 @@
> #include <drm/drm_device.h>
> #include <drm/drm_fb_cma_helper.h>
> #include <drm/drm_gem_cma_helper.h>
> -#include <drm/drm_vblank.h>
> #include <drm/drm_plane_helper.h>
> #include <drm/drm_probe_helper.h>
> #include <linux/clk.h>
> @@ -138,24 +137,9 @@ static void arc_pgu_crtc_atomic_disable(struct drm_crtc *crtc,
> ~ARCPGU_CTRL_ENABLE_MASK);
> }
>
> -static void arc_pgu_crtc_atomic_begin(struct drm_crtc *crtc,
> - struct drm_crtc_state *state)
> -{
> - struct drm_pending_vblank_event *event = crtc->state->event;
> -
> - if (event) {
> - crtc->state->event = NULL;
> -
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> - }
> -}
> -
> static const struct drm_crtc_helper_funcs arc_pgu_crtc_helper_funcs = {
> .mode_valid = arc_pgu_crtc_mode_valid,
> .mode_set_nofb = arc_pgu_crtc_mode_set_nofb,
> - .atomic_begin = arc_pgu_crtc_atomic_begin,
> .atomic_enable = arc_pgu_crtc_atomic_enable,
> .atomic_disable = arc_pgu_crtc_atomic_disable,
> };
> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
> index 3f0006c2470d..ff275faee88d 100644
> --- a/drivers/gpu/drm/bochs/bochs_kms.c
> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
> @@ -7,7 +7,6 @@
> #include <drm/drm_atomic_helper.h>
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>
> #include "bochs.h"
>
> @@ -57,16 +56,8 @@ static void bochs_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct bochs_device *bochs = pipe->crtc.dev->dev_private;
> - struct drm_crtc *crtc = &pipe->crtc;
>
> bochs_plane_update(bochs, pipe->plane.state);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - crtc->state->event = NULL;
> - spin_unlock_irq(&crtc->dev->event_lock);
> - }
> }
>
> static const struct drm_simple_display_pipe_funcs bochs_pipe_funcs = {
> diff --git a/drivers/gpu/drm/cirrus/cirrus.c b/drivers/gpu/drm/cirrus/cirrus.c
> index 248c9f765c45..a91fb0d7282c 100644
> --- a/drivers/gpu/drm/cirrus/cirrus.c
> +++ b/drivers/gpu/drm/cirrus/cirrus.c
> @@ -38,7 +38,6 @@
> #include <drm/drm_modeset_helper_vtables.h>
> #include <drm/drm_probe_helper.h>
> #include <drm/drm_simple_kms_helper.h>
> -#include <drm/drm_vblank.h>
>
> #define DRIVER_NAME "cirrus"
> #define DRIVER_DESC "qemu cirrus vga"
> @@ -434,13 +433,6 @@ static void cirrus_pipe_update(struct drm_simple_display_pipe *pipe,
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> cirrus_fb_blit_rect(pipe->plane.state->fb, &rect);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - crtc->state->event = NULL;
> - spin_unlock_irq(&crtc->dev->event_lock);
> - }
> }
>
> static const struct drm_simple_display_pipe_funcs cirrus_pipe_funcs = {
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 4511c2e07bb9..6e9c730a8919 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -583,6 +583,7 @@ mode_valid(struct drm_atomic_state *state)
> * &drm_crtc_state.connectors_changed is set when a connector is added or
> * removed from the CRTC. &drm_crtc_state.active_changed is set when
> * &drm_crtc_state.active changes, which is used for DPMS.
> + * &drm_crtc_state.no_vblank is set from the result of drm_crtc_has_vblank().
> * See also: drm_atomic_crtc_needs_modeset()
> *
> * IMPORTANT:
> @@ -649,6 +650,11 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
>
> return -EINVAL;
> }
> +
> + if (drm_crtc_has_vblank(crtc))
> + new_crtc_state->no_vblank = false;
> + else
> + new_crtc_state->no_vblank = true;
Yeah this looks much better than my hack :-)
> }
>
> ret = handle_conflicting_encoders(state, false);
> @@ -2215,7 +2221,9 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_dependencies);
> * when a job is queued, and any change to the pipeline that does not touch the
> * connector is leading to timeouts when calling
> * drm_atomic_helper_wait_for_vblanks() or
> - * drm_atomic_helper_wait_for_flip_done().
> + * drm_atomic_helper_wait_for_flip_done(). In addition to writeback
> + * connectors, this function can also fake VBLANK events for CRTCs without
> + * VBLANK interrupt.
I still think we should reword this entire paragraph to make the "hw has
no vblank" the main use-case, with writeback connectors as the "Also used
for ..." special case.
> *
> * This is part of the atomic helper support for nonblocking commits, see
> * drm_atomic_helper_setup_commit() for an overview.
> diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
> index 16bff1be4b8a..13b753cb3f67 100644
> --- a/drivers/gpu/drm/drm_mipi_dbi.c
> +++ b/drivers/gpu/drm/drm_mipi_dbi.c
> @@ -24,7 +24,6 @@
> #include <drm/drm_modes.h>
> #include <drm/drm_probe_helper.h>
> #include <drm/drm_rect.h>
> -#include <drm/drm_vblank.h>
> #include <video/mipi_display.h>
>
> #define MIPI_DBI_MAX_SPI_READ_SPEED 2000000 /* 2MHz */
> @@ -299,18 +298,10 @@ void mipi_dbi_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct drm_plane_state *state = pipe->plane.state;
> - struct drm_crtc *crtc = &pipe->crtc;
> struct drm_rect rect;
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> mipi_dbi_fb_dirty(state->fb, &rect);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> - crtc->state->event = NULL;
> - }
> }
> EXPORT_SYMBOL(mipi_dbi_pipe_update);
>
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index c20102899411..d1d39ae47b0e 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -69,6 +69,12 @@
> * &drm_driver.max_vblank_count. In that case the vblank core only disables the
> * vblanks after a timer has expired, which can be configured through the
> * ``vblankoffdelay`` module parameter.
> + *
> + * Drivers for hardware without support for vertical-blanking interrupts
> + * must not call drm_vblank_init(). For such drivers, atomic helpers will
> + * automatically generate vblank events as part of the display update. This
> + * functionality also can be controlled by the driver by enabling and disabling
> + * struct drm_crtc_state.no_vblank.
> */
>
> /* Retry timestamp calculation up to 3 times to satisfy
> @@ -510,6 +516,9 @@ EXPORT_SYMBOL(drm_vblank_init);
> * initialized for a CRTC. For most hardware this means that vblanking
> * can also be enabled on the CRTC.
> *
> + * Atomic helpers use this function to initialize
> + * &drm_crtc_state.no_vblank. See also drm_atomic_helper_check_modeset().
> + *
> * Returns:
> * True if vblanking has been initialized for the given CRTC, false
> * otherwise.
> diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
> index 16d73b22f3f5..ab4f8dd00400 100644
> --- a/drivers/gpu/drm/qxl/qxl_display.c
> +++ b/drivers/gpu/drm/qxl/qxl_display.c
> @@ -31,7 +31,6 @@
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_plane_helper.h>
> #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>
> #include "qxl_drv.h"
> #include "qxl_object.h"
> @@ -372,19 +371,6 @@ static void qxl_crtc_update_monitors_config(struct drm_crtc *crtc,
> static void qxl_crtc_atomic_flush(struct drm_crtc *crtc,
> struct drm_crtc_state *old_crtc_state)
> {
> - struct drm_device *dev = crtc->dev;
> - struct drm_pending_vblank_event *event;
> - unsigned long flags;
> -
> - if (crtc->state && crtc->state->event) {
> - event = crtc->state->event;
> - crtc->state->event = NULL;
> -
> - spin_lock_irqsave(&dev->event_lock, flags);
> - drm_crtc_send_vblank_event(crtc, event);
> - spin_unlock_irqrestore(&dev->event_lock, flags);
> - }
> -
> qxl_crtc_update_monitors_config(crtc, "flush");
> }
>
> diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c
> index 94fb1f593564..a48173441ae0 100644
> --- a/drivers/gpu/drm/tiny/gm12u320.c
> +++ b/drivers/gpu/drm/tiny/gm12u320.c
> @@ -22,7 +22,6 @@
> #include <drm/drm_modeset_helper_vtables.h>
> #include <drm/drm_probe_helper.h>
> #include <drm/drm_simple_kms_helper.h>
> -#include <drm/drm_vblank.h>
>
> static bool eco_mode;
> module_param(eco_mode, bool, 0644);
> @@ -610,18 +609,10 @@ static void gm12u320_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct drm_plane_state *state = pipe->plane.state;
> - struct drm_crtc *crtc = &pipe->crtc;
> struct drm_rect rect;
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> gm12u320_fb_mark_dirty(pipe->plane.state->fb, &rect);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - crtc->state->event = NULL;
> - spin_unlock_irq(&crtc->dev->event_lock);
> - }
> }
>
> static const struct drm_simple_display_pipe_funcs gm12u320_pipe_funcs = {
> diff --git a/drivers/gpu/drm/tiny/ili9225.c b/drivers/gpu/drm/tiny/ili9225.c
> index c66acc566c2b..802fb8dde1b6 100644
> --- a/drivers/gpu/drm/tiny/ili9225.c
> +++ b/drivers/gpu/drm/tiny/ili9225.c
> @@ -26,7 +26,6 @@
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_mipi_dbi.h>
> #include <drm/drm_rect.h>
> -#include <drm/drm_vblank.h>
>
> #define ILI9225_DRIVER_READ_CODE 0x00
> #define ILI9225_DRIVER_OUTPUT_CONTROL 0x01
> @@ -165,18 +164,10 @@ static void ili9225_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct drm_plane_state *state = pipe->plane.state;
> - struct drm_crtc *crtc = &pipe->crtc;
> struct drm_rect rect;
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> ili9225_fb_dirty(state->fb, &rect);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> - crtc->state->event = NULL;
> - }
> }
>
> static void ili9225_pipe_enable(struct drm_simple_display_pipe *pipe,
> diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/repaper.c
> index 76d179200775..183484595aea 100644
> --- a/drivers/gpu/drm/tiny/repaper.c
> +++ b/drivers/gpu/drm/tiny/repaper.c
> @@ -33,7 +33,6 @@
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_modes.h>
> #include <drm/drm_rect.h>
> -#include <drm/drm_vblank.h>
> #include <drm/drm_probe_helper.h>
> #include <drm/drm_simple_kms_helper.h>
>
> @@ -856,18 +855,10 @@ static void repaper_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct drm_plane_state *state = pipe->plane.state;
> - struct drm_crtc *crtc = &pipe->crtc;
> struct drm_rect rect;
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> repaper_fb_dirty(state->fb);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> - crtc->state->event = NULL;
> - }
> }
>
> static const struct drm_simple_display_pipe_funcs repaper_pipe_funcs = {
> diff --git a/drivers/gpu/drm/tiny/st7586.c b/drivers/gpu/drm/tiny/st7586.c
> index 060cc756194f..9ef559dd3191 100644
> --- a/drivers/gpu/drm/tiny/st7586.c
> +++ b/drivers/gpu/drm/tiny/st7586.c
> @@ -23,7 +23,6 @@
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_mipi_dbi.h>
> #include <drm/drm_rect.h>
> -#include <drm/drm_vblank.h>
>
> /* controller-specific commands */
> #define ST7586_DISP_MODE_GRAY 0x38
> @@ -159,18 +158,10 @@ static void st7586_pipe_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_state)
> {
> struct drm_plane_state *state = pipe->plane.state;
> - struct drm_crtc *crtc = &pipe->crtc;
> struct drm_rect rect;
>
> if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> st7586_fb_dirty(state->fb, &rect);
> -
> - if (crtc->state->event) {
> - spin_lock_irq(&crtc->dev->event_lock);
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> - crtc->state->event = NULL;
> - }
> }
>
> static void st7586_pipe_enable(struct drm_simple_display_pipe *pipe,
> diff --git a/drivers/gpu/drm/vboxvideo/vbox_mode.c b/drivers/gpu/drm/vboxvideo/vbox_mode.c
> index 19612132c8a3..8b7f005c4d20 100644
> --- a/drivers/gpu/drm/vboxvideo/vbox_mode.c
> +++ b/drivers/gpu/drm/vboxvideo/vbox_mode.c
> @@ -18,7 +18,6 @@
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_plane_helper.h>
> #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>
> #include "hgsmi_channels.h"
> #include "vbox_drv.h"
> @@ -226,17 +225,6 @@ static void vbox_crtc_atomic_disable(struct drm_crtc *crtc,
> static void vbox_crtc_atomic_flush(struct drm_crtc *crtc,
> struct drm_crtc_state *old_crtc_state)
> {
> - struct drm_pending_vblank_event *event;
> - unsigned long flags;
> -
> - if (crtc->state && crtc->state->event) {
> - event = crtc->state->event;
> - crtc->state->event = NULL;
> -
> - spin_lock_irqsave(&crtc->dev->event_lock, flags);
> - drm_crtc_send_vblank_event(crtc, event);
> - spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
> - }
> }
>
> static const struct drm_crtc_helper_funcs vbox_crtc_helper_funcs = {
> diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c
> index 0966208ec30d..ecf4ba7cc32b 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_display.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_display.c
> @@ -30,7 +30,6 @@
> #include <drm/drm_fourcc.h>
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>
> #include "virtgpu_drv.h"
>
> @@ -121,13 +120,6 @@ static int virtio_gpu_crtc_atomic_check(struct drm_crtc *crtc,
> static void virtio_gpu_crtc_atomic_flush(struct drm_crtc *crtc,
> struct drm_crtc_state *old_state)
> {
> - unsigned long flags;
> -
> - spin_lock_irqsave(&crtc->dev->event_lock, flags);
> - if (crtc->state->event)
> - drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - crtc->state->event = NULL;
> - spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
> }
>
> static const struct drm_crtc_helper_funcs virtio_gpu_crtc_helper_funcs = {
> diff --git a/drivers/gpu/drm/xen/xen_drm_front_kms.c b/drivers/gpu/drm/xen/xen_drm_front_kms.c
> index 4f34c5208180..efde4561836f 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front_kms.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front_kms.c
> @@ -220,6 +220,18 @@ static bool display_send_page_flip(struct drm_simple_display_pipe *pipe,
> return false;
> }
>
> +static int display_check(struct drm_simple_display_pipe *pipe,
> + struct drm_plane_state *plane_state,
> + struct drm_crtc_state *crtc_state)
> +{
> + /* Make sure that DRM helpers don't send VBLANK events
> + * automatically. Xen has it's own logic to do so.
> + */
> + crtc_state->no_vblank = false;
> +
> + return 0;
> +}
> +
> static void display_update(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_plane_state)
> {
> @@ -284,6 +296,7 @@ static const struct drm_simple_display_pipe_funcs display_funcs = {
> .enable = display_enable,
> .disable = display_disable,
> .prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
> + .check = display_check,
> .update = display_update,
> };
>
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 5e9b15a0e8c5..5363e31c9abe 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -174,12 +174,22 @@ struct drm_crtc_state {
> * @no_vblank:
> *
> * Reflects the ability of a CRTC to send VBLANK events. This state
> - * usually depends on the pipeline configuration, and the main usuage
> - * is CRTCs feeding a writeback connector operating in oneshot mode.
> - * In this case the VBLANK event is only generated when a job is queued
> - * to the writeback connector, and we want the core to fake VBLANK
> - * events when this part of the pipeline hasn't changed but others had
> - * or when the CRTC and connectors are being disabled.
> + * usually depends on the pipeline configuration. If set to true, DRM
> + * atomic helpers will sendout a fake VBLANK event during display
> + * updates.
> + *
> + * One usage is for drivers and/or hardware without support for VBLANK
> + * interrupts. Such drivers typically do not initialize vblanking
> + * (i.e., call drm_vblank_init() wit the number of CRTCs). For CRTCs
> + * without initialized vblanking, the field is initialized to true and
... is initialized to true in the atomic helpers by calling
drm_atomic_helper_check_modeset() and ...
Just to clarify that this isn't done for everyone by default, but a helper
thing.
> + * a VBLANK event will be send out on each update of the display
> + * pipeline.
> + *
> + * Another usage is CRTCs feeding a writeback connector operating in
> + * oneshot mode. In this case the VBLANK event is only generated when
> + * a job is queued to the writeback connector, and we want the core
> + * to fake VBLANK events when this part of the pipeline hasn't changed
> + * but others had or when the CRTC and connectors are being disabled.
> *
> * __drm_atomic_helper_crtc_duplicate_state() will not reset the value
> * from the current state, the CRTC driver is then responsible for
> @@ -335,7 +345,10 @@ struct drm_crtc_state {
> * - Events for disabled CRTCs are not allowed, and drivers can ignore
> * that case.
> *
> - * This can be handled by the drm_crtc_send_vblank_event() function,
> + * For very simple hardware without VBLANK interrupt, enabling
> + * &struct drm_crtc_state.no_vblank makes DRM's atomic commit helpers
> + * send the event at an appropriate time. For more complex hardware this
> + * can be handled by the drm_crtc_send_vblank_event() function,
> * which the driver should call on the provided event upon completion of
> * the atomic commit. Note that if the driver supports vblank signalling
> * and timestamping the vblank counters and timestamps must agree with
> diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
> index 15afee9cf049..e253ba7bea9d 100644
> --- a/include/drm/drm_simple_kms_helper.h
> +++ b/include/drm/drm_simple_kms_helper.h
> @@ -100,8 +100,11 @@ struct drm_simple_display_pipe_funcs {
> * This is the function drivers should submit the
> * &drm_pending_vblank_event from. Using either
> * drm_crtc_arm_vblank_event(), when the driver supports vblank
> - * interrupt handling, or drm_crtc_send_vblank_event() directly in case
> - * the hardware lacks vblank support entirely.
> + * interrupt handling, or drm_crtc_send_vblank_event() for more
> + * complex case. In case the hardware lacks vblank support entirely,
> + * drivers can set &struct drm_crtc_state.no_vblank in
> + * &struct drm_simple_display_pipe_funcs.check and let DRM's
> + * atomic helper fake a vblank event.
> */
> void (*update)(struct drm_simple_display_pipe *pipe,
> struct drm_plane_state *old_plane_state);
With the kerneldoc fixed, for the core parts of this patch (driver changes
all split out):
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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