[Xen-devel] [PATCH v3 0/4] Use no_vblank property for drivers without VBLANK

[Xen-devel] [PATCH v3 0/4] Use no_vblank property for drivers without VBLANK

[Thomas Zimmermann]

Instead of faking VBLANK events by themselves, drivers without VBLANK
support can enable drm_crtc_vblank.no_vblank and let DRM do the rest.
The patchset makes this official and converts over drivers.

The current implementation looks at the number of initialized CRTCs
wrt vblanking. If vblanking has been initialized for a CRTC, the driver
is responsible for sending out VBLANK events. Otherwise, DRM will send
out the event. The behaviour selected by initializing no_vblank as part
of drm_atomic_helper_check_modeset().

I went through all drivers, looking for those that call send out VBLANK
events but do not call drm_vblank_init(). These are converted to the new
semantics. This affects tiny drivers; drivers for virtual hardware; and
a few others, which do not support interrupts. Xen comes with its
own VBLANK logic and disables no_vblank explictly.

For now, I left out Hans' R-b on v2 of the series, as the patches changed
quite a bit.

v3:
	* reorder and squash patches
	* set no_vblank in drm_atomic_helper_check_modeset() for *all*
	  drivers (Daniel)
	* convert all drivers to new semnatics as necessary
v2:
	* document functionality (Daniel)
	* cleanup ast (Daniel)
	* let simple-kms handle no_vblank where possible

Thomas Zimmermann (4):
  drm: Add drm_crtc_has_vblank()
  drm: Initialize struct drm_crtc_state.no_vblank from device settings
  drm/ast: Don't set struct drm_crtc_state.no_vblank explictly
  drm/udl: Don't set struct drm_crtc_state.no_vblank explictly

 drivers/gpu/drm/arc/arcpgu_crtc.c        | 16 -------------
 drivers/gpu/drm/ast/ast_mode.c           |  2 --
 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             | 30 ++++++++++++++++++++++++
 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/udl/udl_modeset.c        | 11 ---------
 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 ++++--
 include/drm/drm_vblank.h                 |  1 +
 19 files changed, 78 insertions(+), 135 deletions(-)

--
2.24.1


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[Xen-devel] [PATCH v3 1/4] drm: Add drm_crtc_has_vblank()

[Thomas Zimmermann]

The new interface drm_crtc_has_vblank() return true if vblanking has
been initialized for a certain CRTC, or false otherwise. This function
will be useful for initializing CRTC state.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_vblank.c | 21 +++++++++++++++++++++
 include/drm/drm_vblank.h     |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 1659b13b178c..c20102899411 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -501,6 +501,27 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
 }
 EXPORT_SYMBOL(drm_vblank_init);
 
+/**
+ * drm_crtc_has_vblank - test if vblanking has been initialized for
+ *                       a CRTC
+ * @crtc: the CRTC
+ *
+ * Drivers may call this function to test if vblank support is
+ * initialized for a CRTC. For most hardware this means that vblanking
+ * can also be enabled on the CRTC.
+ *
+ * Returns:
+ * True if vblanking has been initialized for the given CRTC, false
+ * otherwise.
+ */
+bool drm_crtc_has_vblank(const struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+
+	return crtc->index < dev->num_crtcs;
+}
+EXPORT_SYMBOL(drm_crtc_has_vblank);
+
 /**
  * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
  * @crtc: which CRTC's vblank waitqueue to retrieve
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index c16c44052b3d..531a6bc12b7e 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -206,6 +206,7 @@ struct drm_vblank_crtc {
 };
 
 int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
+bool drm_crtc_has_vblank(const struct drm_crtc *crtc);
 u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
 u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
 				   ktime_t *vblanktime);
-- 
2.24.1


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[Xen-devel] [PATCH v3 2/4] drm: Initialize struct drm_crtc_state.no_vblank from device settings

[Thomas Zimmermann]

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

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 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;
 	}
 
 	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.
  *
  * 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
+	 * 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);
-- 
2.24.1


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[Xen-devel] [PATCH v3 3/4] drm/ast: Don't set struct drm_crtc_state.no_vblank explictly

[Thomas Zimmermann]

As ast does not initialize vblanking, atomic helpers initialize the
value of struct drm_crtc_state.no_vblank to be true. No need to set
it from within the driver.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/ast/ast_mode.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 34608f0499eb..7810a84e7e9e 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -833,8 +833,6 @@ static void ast_crtc_helper_atomic_flush(struct drm_crtc *crtc,
 	struct ast_vbios_mode_info *vbios_mode_info;
 	struct drm_display_mode *adjusted_mode;
 
-	crtc->state->no_vblank = true;
-
 	ast_state = to_ast_crtc_state(crtc->state);
 
 	format = ast_state->format;
-- 
2.24.1


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[Xen-devel] [PATCH v3 4/4] drm/udl: Don't set struct drm_crtc_state.no_vblank explictly

[Thomas Zimmermann]

As udl does not initialize vblanking, atomic helpers initialize the
value of struct drm_crtc_state.no_vblank to be true. No need to set
it from within the driver.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/udl/udl_modeset.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
index 22af17959053..d59ebac70b15 100644
--- a/drivers/gpu/drm/udl/udl_modeset.c
+++ b/drivers/gpu/drm/udl/udl_modeset.c
@@ -375,8 +375,6 @@ udl_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 	char *wrptr;
 	int color_depth = UDL_COLOR_DEPTH_16BPP;
 
-	crtc_state->no_vblank = true;
-
 	buf = (char *)udl->mode_buf;
 
 	/* This first section has to do with setting the base address on the
@@ -428,14 +426,6 @@ udl_simple_display_pipe_disable(struct drm_simple_display_pipe *pipe)
 	udl_submit_urb(dev, urb, buf - (char *)urb->transfer_buffer);
 }
 
-static int
-udl_simple_display_pipe_check(struct drm_simple_display_pipe *pipe,
-			      struct drm_plane_state *plane_state,
-			      struct drm_crtc_state *crtc_state)
-{
-	return 0;
-}
-
 static void
 udl_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 			       struct drm_plane_state *old_plane_state)
@@ -457,7 +447,6 @@ struct drm_simple_display_pipe_funcs udl_simple_display_pipe_funcs = {
 	.mode_valid = udl_simple_display_pipe_mode_valid,
 	.enable = udl_simple_display_pipe_enable,
 	.disable = udl_simple_display_pipe_disable,
-	.check = udl_simple_display_pipe_check,
 	.update = udl_simple_display_pipe_update,
 	.prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
 };
-- 
2.24.1


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Re: [Xen-devel] [PATCH v3 0/4] Use no_vblank property for drivers without VBLANK

[Gerd Hoffmann]

On Mon, Jan 20, 2020 at 01:20:47PM +0100, Thomas Zimmermann wrote:
> Instead of faking VBLANK events by themselves, drivers without VBLANK
> support can enable drm_crtc_vblank.no_vblank and let DRM do the rest.
> The patchset makes this official and converts over drivers.
> 
> The current implementation looks at the number of initialized CRTCs
> wrt vblanking. If vblanking has been initialized for a CRTC, the driver
> is responsible for sending out VBLANK events. Otherwise, DRM will send
> out the event. The behaviour selected by initializing no_vblank as part
> of drm_atomic_helper_check_modeset().
> 
> I went through all drivers, looking for those that call send out VBLANK
> events but do not call drm_vblank_init(). These are converted to the new
> semantics. This affects tiny drivers; drivers for virtual hardware; and
> a few others, which do not support interrupts. Xen comes with its
> own VBLANK logic and disables no_vblank explictly.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>


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Re: [Xen-devel] [PATCH v3 1/4] drm: Add drm_crtc_has_vblank()

[Daniel Vetter]

On Mon, Jan 20, 2020 at 01:20:48PM +0100, Thomas Zimmermann wrote:
> The new interface drm_crtc_has_vblank() return true if vblanking has
> been initialized for a certain CRTC, or false otherwise. This function
> will be useful for initializing CRTC state.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_vblank.c | 21 +++++++++++++++++++++
>  include/drm/drm_vblank.h     |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 1659b13b178c..c20102899411 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -501,6 +501,27 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
>  }
>  EXPORT_SYMBOL(drm_vblank_init);
>  
> +/**
> + * drm_crtc_has_vblank - test if vblanking has been initialized for
> + *                       a CRTC
> + * @crtc: the CRTC
> + *
> + * Drivers may call this function to test if vblank support is
> + * initialized for a CRTC. For most hardware this means that vblanking
> + * can also be enabled on the CRTC.
> + *
> + * Returns:
> + * True if vblanking has been initialized for the given CRTC, false
> + * otherwise.
> + */
> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc)

So making this specific to a CRTC sounds like a good idea. But it's not
the reality, drm_vblank.c assumes that either everything or nothing
supports vblanks.

The reason for dev->num_crtcs is historical baggage, it predates kms by a
few years. For kms drivers the only two valid values are either 0 or
dev->mode_config.num_crtcs. Yes that's an entire different can of worms
that's been irking me since forever (ideally drm_vblank_init would somehow
loose the num_crtcs argument for kms drivers, but some drivers call this
before they've done all the drm_crtc_init calls so it's complicated).

Hence drm_dev_has_vblank as I suggested. That would also allow you to
replace a bunch of if (dev->num_crtcs) checks in drm_vblank.c, which
should help quite a bit in code readability.

Cheers, Daniel

> +{
> +	struct drm_device *dev = crtc->dev;
> +
> +	return crtc->index < dev->num_crtcs;
> +}
> +EXPORT_SYMBOL(drm_crtc_has_vblank);
> +
>  /**
>   * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
>   * @crtc: which CRTC's vblank waitqueue to retrieve
> diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
> index c16c44052b3d..531a6bc12b7e 100644
> --- a/include/drm/drm_vblank.h
> +++ b/include/drm/drm_vblank.h
> @@ -206,6 +206,7 @@ struct drm_vblank_crtc {
>  };
>  
>  int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc);
>  u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
>  u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
>  				   ktime_t *vblanktime);
> -- 
> 2.24.1
> 

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

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Re: [Xen-devel] [PATCH v3 2/4] drm: Initialize struct drm_crtc_state.no_vblank from device settings

[Daniel Vetter]

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@suse.de>
> ---
>  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@ffwll.ch>
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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Re: [Xen-devel] [PATCH v3 1/4] drm: Add drm_crtc_has_vblank()

[Thomas Zimmermann]

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Hi

Am 22.01.20 um 09:31 schrieb Daniel Vetter:
> On Mon, Jan 20, 2020 at 01:20:48PM +0100, Thomas Zimmermann wrote:
>> The new interface drm_crtc_has_vblank() return true if vblanking has
>> been initialized for a certain CRTC, or false otherwise. This function
>> will be useful for initializing CRTC state.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>  drivers/gpu/drm/drm_vblank.c | 21 +++++++++++++++++++++
>>  include/drm/drm_vblank.h     |  1 +
>>  2 files changed, 22 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
>> index 1659b13b178c..c20102899411 100644
>> --- a/drivers/gpu/drm/drm_vblank.c
>> +++ b/drivers/gpu/drm/drm_vblank.c
>> @@ -501,6 +501,27 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
>>  }
>>  EXPORT_SYMBOL(drm_vblank_init);
>>  
>> +/**
>> + * drm_crtc_has_vblank - test if vblanking has been initialized for
>> + *                       a CRTC
>> + * @crtc: the CRTC
>> + *
>> + * Drivers may call this function to test if vblank support is
>> + * initialized for a CRTC. For most hardware this means that vblanking
>> + * can also be enabled on the CRTC.
>> + *
>> + * Returns:
>> + * True if vblanking has been initialized for the given CRTC, false
>> + * otherwise.
>> + */
>> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc)
> 
> So making this specific to a CRTC sounds like a good idea. But it's not
> the reality, drm_vblank.c assumes that either everything or nothing
> supports vblanks.
> 
> The reason for dev->num_crtcs is historical baggage, it predates kms by a
> few years. For kms drivers the only two valid values are either 0 or
> dev->mode_config.num_crtcs. Yes that's an entire different can of worms
> that's been irking me since forever (ideally drm_vblank_init would somehow
> loose the num_crtcs argument for kms drivers, but some drivers call this
> before they've done all the drm_crtc_init calls so it's complicated).

Maybe as a first step, drm_vblank_init() could use
dev->mode_config.num_crtcs if the supplied number of CRTCs is zero.

> 
> Hence drm_dev_has_vblank as I suggested. That would also allow you to
> replace a bunch of if (dev->num_crtcs) checks in drm_vblank.c, which
> should help quite a bit in code readability.

OK, but I still don't understand why this interface is better overall.
We don't loose anything by passing in the crtc instead of the device
structure. And if there's ever a per-crtc vblank initialization, we'd
have the interface in place already. The tests with "if
(dev->num_crtcs)" could probably be removed in most places in any case.

We should also consider forking the vblank code for non-KMS drivers.
While working in this, I found the support for legacy drivers is getting
in the way at times. With such a fork, legacy drivers could continue
using struct drm_vblank_crtc, while modern drivers could maybe store
vblank state directly in struct drm_crtc.

Anyway, all this is for another patch. Unless you change your mind, I'll
replace drm_crtc_has_vblank() with drm_dev_has_vblank() for the
patchset's next iteration.

Best regards
Thomas

> 
> Cheers, Daniel
> 
>> +{
>> +	struct drm_device *dev = crtc->dev;
>> +
>> +	return crtc->index < dev->num_crtcs;
>> +}
>> +EXPORT_SYMBOL(drm_crtc_has_vblank);
>> +
>>  /**
>>   * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
>>   * @crtc: which CRTC's vblank waitqueue to retrieve
>> diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
>> index c16c44052b3d..531a6bc12b7e 100644
>> --- a/include/drm/drm_vblank.h
>> +++ b/include/drm/drm_vblank.h
>> @@ -206,6 +206,7 @@ struct drm_vblank_crtc {
>>  };
>>  
>>  int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
>> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc);
>>  u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
>>  u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
>>  				   ktime_t *vblanktime);
>> -- 
>> 2.24.1
>>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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Re: [Xen-devel] [PATCH v3 1/4] drm: Add drm_crtc_has_vblank()

[Daniel Vetter]

On Wed, Jan 22, 2020 at 09:53:42AM +0100, Thomas Zimmermann wrote:
> Hi
> 
> Am 22.01.20 um 09:31 schrieb Daniel Vetter:
> > On Mon, Jan 20, 2020 at 01:20:48PM +0100, Thomas Zimmermann wrote:
> >> The new interface drm_crtc_has_vblank() return true if vblanking has
> >> been initialized for a certain CRTC, or false otherwise. This function
> >> will be useful for initializing CRTC state.
> >>
> >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> >> ---
> >>  drivers/gpu/drm/drm_vblank.c | 21 +++++++++++++++++++++
> >>  include/drm/drm_vblank.h     |  1 +
> >>  2 files changed, 22 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> >> index 1659b13b178c..c20102899411 100644
> >> --- a/drivers/gpu/drm/drm_vblank.c
> >> +++ b/drivers/gpu/drm/drm_vblank.c
> >> @@ -501,6 +501,27 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
> >>  }
> >>  EXPORT_SYMBOL(drm_vblank_init);
> >>  
> >> +/**
> >> + * drm_crtc_has_vblank - test if vblanking has been initialized for
> >> + *                       a CRTC
> >> + * @crtc: the CRTC
> >> + *
> >> + * Drivers may call this function to test if vblank support is
> >> + * initialized for a CRTC. For most hardware this means that vblanking
> >> + * can also be enabled on the CRTC.
> >> + *
> >> + * Returns:
> >> + * True if vblanking has been initialized for the given CRTC, false
> >> + * otherwise.
> >> + */
> >> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc)
> > 
> > So making this specific to a CRTC sounds like a good idea. But it's not
> > the reality, drm_vblank.c assumes that either everything or nothing
> > supports vblanks.
> > 
> > The reason for dev->num_crtcs is historical baggage, it predates kms by a
> > few years. For kms drivers the only two valid values are either 0 or
> > dev->mode_config.num_crtcs. Yes that's an entire different can of worms
> > that's been irking me since forever (ideally drm_vblank_init would somehow
> > loose the num_crtcs argument for kms drivers, but some drivers call this
> > before they've done all the drm_crtc_init calls so it's complicated).
> 
> Maybe as a first step, drm_vblank_init() could use
> dev->mode_config.num_crtcs if the supplied number of CRTCs is zero.
> 
> > 
> > Hence drm_dev_has_vblank as I suggested. That would also allow you to
> > replace a bunch of if (dev->num_crtcs) checks in drm_vblank.c, which
> > should help quite a bit in code readability.
> 
> OK, but I still don't understand why this interface is better overall.
> We don't loose anything by passing in the crtc instead of the device
> structure. And if there's ever a per-crtc vblank initialization, we'd
> have the interface in place already. The tests with "if
> (dev->num_crtcs)" could probably be removed in most places in any case.

You can't use it in drm_vblank.c code, because we only have the
drm_device, not the drm_crtc (in most places at least). Your other patch
series to deprecate the drm_device callbacks for vblanks is a huge step
into the direction to fix that, but still more work needed: We'd
essentially need to copypaste drm_vblank.c into drm_crtc_vblank.c for kms
drivers, and in that copy switch from (dev, pipe) to crtc everywhere. Plus
then move the drm_vblank structure into struct drm_crtc.

Wrt removing the check: In a pile of cases it changes the return value,
which matters both for vblank usage in helper code and the ioctl itself.
From a quick look most of the checks that don't matter are already wrapped
in a WARN.

> We should also consider forking the vblank code for non-KMS drivers.
> While working in this, I found the support for legacy drivers is getting
> in the way at times. With such a fork, legacy drivers could continue
> using struct drm_vblank_crtc, while modern drivers could maybe store
> vblank state directly in struct drm_crtc.

Hm if you want to do all that then the drm_crtc_has_vblank makes sense.
But only after we've done the full split. So maybe make the public
function drm_crtc_has_vblank, which calls the internal-only
drm_has_vblank, and use that internally in drm_vblank.c?

btw I still think a sub-struct for vblank stuff in drm_crtc makes sense,
and drm_vblank_crtc seems to mostly fit the bill.

That way we're at least not adding the the conversion pain of switching
the vblank code over to drm_crtc fully.

Thoughts?
-Daniel

> Anyway, all this is for another patch. Unless you change your mind, I'll
> replace drm_crtc_has_vblank() with drm_dev_has_vblank() for the
> patchset's next iteration.
> 
> Best regards
> Thomas
> 
> > 
> > Cheers, Daniel
> > 
> >> +{
> >> +	struct drm_device *dev = crtc->dev;
> >> +
> >> +	return crtc->index < dev->num_crtcs;
> >> +}
> >> +EXPORT_SYMBOL(drm_crtc_has_vblank);
> >> +
> >>  /**
> >>   * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
> >>   * @crtc: which CRTC's vblank waitqueue to retrieve
> >> diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
> >> index c16c44052b3d..531a6bc12b7e 100644
> >> --- a/include/drm/drm_vblank.h
> >> +++ b/include/drm/drm_vblank.h
> >> @@ -206,6 +206,7 @@ struct drm_vblank_crtc {
> >>  };
> >>  
> >>  int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
> >> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc);
> >>  u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
> >>  u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
> >>  				   ktime_t *vblanktime);
> >> -- 
> >> 2.24.1
> >>
> > 
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
> 




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

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Re: [Xen-devel] [PATCH v3 1/4] drm: Add drm_crtc_has_vblank()

[Thomas Zimmermann]

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Hi

Am 22.01.20 um 10:04 schrieb Daniel Vetter:
> On Wed, Jan 22, 2020 at 09:53:42AM +0100, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 22.01.20 um 09:31 schrieb Daniel Vetter:
>>> On Mon, Jan 20, 2020 at 01:20:48PM +0100, Thomas Zimmermann wrote:
>>>> The new interface drm_crtc_has_vblank() return true if vblanking has
>>>> been initialized for a certain CRTC, or false otherwise. This function
>>>> will be useful for initializing CRTC state.
>>>>
>>>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>>>> ---
>>>>  drivers/gpu/drm/drm_vblank.c | 21 +++++++++++++++++++++
>>>>  include/drm/drm_vblank.h     |  1 +
>>>>  2 files changed, 22 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
>>>> index 1659b13b178c..c20102899411 100644
>>>> --- a/drivers/gpu/drm/drm_vblank.c
>>>> +++ b/drivers/gpu/drm/drm_vblank.c
>>>> @@ -501,6 +501,27 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
>>>>  }
>>>>  EXPORT_SYMBOL(drm_vblank_init);
>>>>  
>>>> +/**
>>>> + * drm_crtc_has_vblank - test if vblanking has been initialized for
>>>> + *                       a CRTC
>>>> + * @crtc: the CRTC
>>>> + *
>>>> + * Drivers may call this function to test if vblank support is
>>>> + * initialized for a CRTC. For most hardware this means that vblanking
>>>> + * can also be enabled on the CRTC.
>>>> + *
>>>> + * Returns:
>>>> + * True if vblanking has been initialized for the given CRTC, false
>>>> + * otherwise.
>>>> + */
>>>> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc)
>>>
>>> So making this specific to a CRTC sounds like a good idea. But it's not
>>> the reality, drm_vblank.c assumes that either everything or nothing
>>> supports vblanks.
>>>
>>> The reason for dev->num_crtcs is historical baggage, it predates kms by a
>>> few years. For kms drivers the only two valid values are either 0 or
>>> dev->mode_config.num_crtcs. Yes that's an entire different can of worms
>>> that's been irking me since forever (ideally drm_vblank_init would somehow
>>> loose the num_crtcs argument for kms drivers, but some drivers call this
>>> before they've done all the drm_crtc_init calls so it's complicated).
>>
>> Maybe as a first step, drm_vblank_init() could use
>> dev->mode_config.num_crtcs if the supplied number of CRTCs is zero.
>>
>>>
>>> Hence drm_dev_has_vblank as I suggested. That would also allow you to
>>> replace a bunch of if (dev->num_crtcs) checks in drm_vblank.c, which
>>> should help quite a bit in code readability.
>>
>> OK, but I still don't understand why this interface is better overall.
>> We don't loose anything by passing in the crtc instead of the device
>> structure. And if there's ever a per-crtc vblank initialization, we'd
>> have the interface in place already. The tests with "if
>> (dev->num_crtcs)" could probably be removed in most places in any case.
> 
> You can't use it in drm_vblank.c code, because we only have the
> drm_device, not the drm_crtc (in most places at least). Your other patch
> series to deprecate the drm_device callbacks for vblanks is a huge step
> into the direction to fix that, but still more work needed: We'd
> essentially need to copypaste drm_vblank.c into drm_crtc_vblank.c for kms
> drivers, and in that copy switch from (dev, pipe) to crtc everywhere. Plus
> then move the drm_vblank structure into struct drm_crtc.
> 
> Wrt removing the check: In a pile of cases it changes the return value,
> which matters both for vblank usage in helper code and the ioctl itself.
> From a quick look most of the checks that don't matter are already wrapped
> in a WARN.
> 
>> We should also consider forking the vblank code for non-KMS drivers.
>> While working in this, I found the support for legacy drivers is getting
>> in the way at times. With such a fork, legacy drivers could continue
>> using struct drm_vblank_crtc, while modern drivers could maybe store
>> vblank state directly in struct drm_crtc.
> 
> Hm if you want to do all that then the drm_crtc_has_vblank makes sense.
> But only after we've done the full split. So maybe make the public
> function drm_crtc_has_vblank, which calls the internal-only
> drm_has_vblank, and use that internally in drm_vblank.c?
> 
> btw I still think a sub-struct for vblank stuff in drm_crtc makes sense,
> and drm_vblank_crtc seems to mostly fit the bill.
> 
> That way we're at least not adding the the conversion pain of switching
> the vblank code over to drm_crtc fully.
> 
> Thoughts?

That all sounds good. Using struct drm_vblank_crtc with legacy and
modern vblank functions, might allow us to continue to share some of the
implementation.

Wrt the current interface, drm_dev_has_vblank() is only called in a
single place, so switching to drm_crtc_has_vblank() later would not be hard.

Best regards
Thomas

> -Daniel
> 
>> Anyway, all this is for another patch. Unless you change your mind, I'll
>> replace drm_crtc_has_vblank() with drm_dev_has_vblank() for the
>> patchset's next iteration.
>>
>> Best regards
>> Thomas
>>
>>>
>>> Cheers, Daniel
>>>
>>>> +{
>>>> +	struct drm_device *dev = crtc->dev;
>>>> +
>>>> +	return crtc->index < dev->num_crtcs;
>>>> +}
>>>> +EXPORT_SYMBOL(drm_crtc_has_vblank);
>>>> +
>>>>  /**
>>>>   * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
>>>>   * @crtc: which CRTC's vblank waitqueue to retrieve
>>>> diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
>>>> index c16c44052b3d..531a6bc12b7e 100644
>>>> --- a/include/drm/drm_vblank.h
>>>> +++ b/include/drm/drm_vblank.h
>>>> @@ -206,6 +206,7 @@ struct drm_vblank_crtc {
>>>>  };
>>>>  
>>>>  int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
>>>> +bool drm_crtc_has_vblank(const struct drm_crtc *crtc);
>>>>  u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
>>>>  u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
>>>>  				   ktime_t *vblanktime);
>>>> -- 
>>>> 2.24.1
>>>>
>>>
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Felix Imendörffer
>>
> 
> 
> 
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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Re: [Xen-devel] [PATCH v3 0/4] Use no_vblank property for drivers without VBLANK

[Thomas Zimmermann]

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Hi

Am 21.01.20 um 10:36 schrieb Gerd Hoffmann:
> On Mon, Jan 20, 2020 at 01:20:47PM +0100, Thomas Zimmermann wrote:
>> Instead of faking VBLANK events by themselves, drivers without VBLANK
>> support can enable drm_crtc_vblank.no_vblank and let DRM do the rest.
>> The patchset makes this official and converts over drivers.
>>
>> The current implementation looks at the number of initialized CRTCs
>> wrt vblanking. If vblanking has been initialized for a CRTC, the driver
>> is responsible for sending out VBLANK events. Otherwise, DRM will send
>> out the event. The behaviour selected by initializing no_vblank as part
>> of drm_atomic_helper_check_modeset().
>>
>> I went through all drivers, looking for those that call send out VBLANK
>> events but do not call drm_vblank_init(). These are converted to the new
>> semantics. This affects tiny drivers; drivers for virtual hardware; and
>> a few others, which do not support interrupts. Xen comes with its
>> own VBLANK logic and disables no_vblank explictly.
> 
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>

Thanks a lot. v4 will mostly reorganize the patches so I'll keep your A-b.

Best regards
Thomas

> 
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> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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