[PATCH V4 2/2] drm/vkms: Add support for virtual hardware mode

[Sumera Priyadarsini]

Add a virtual hardware or vblank-less mode as a module to
enable VKMS to emulate virtual graphic drivers.

Add a new drm_crtc_helper_funcs struct,
vkms_virtual_crtc_helper_funcs() which holds the atomic helpers
for virtual hardware mode. Change the existing
vkms_crtc_helper_funcs struct to vkms_vblank_crtc_helper_funcs
which holds atomic helpers for the vblank mode.
This makes the code flow clearer and easier to test
virtual hardware mode.

The first patch of this patchset added the function vkms_crtc_composer()
for plane composition which is used in case of vblank-less mode and
is directly called in the atomic hook in vkms_crtc_atomic_begin().
However, some crc captures still use vblanks which causes the crc-based
igt tests to crash. Currently, I am unsure about how to approach the
one-shot implementation of crc reads so I am still working on that.

This patchset has been tested with the igt tests- kms_writeback, kms_atomic,
kms_lease, kms_flip, kms_pipe_get_crc and preserves results except for
subtests related to crc reads and skips tests that rely on vertical
blanking. This patchset must be tested after incorporating the
igt-tests patch:
https://lists.freedesktop.org/archives/igt-dev/2021-February/029355.html .

The patch is based on Rodrigo Siqueira's
patch(https://patchwork.freedesktop.org/patch/316851/?series=48469&rev=3)
and the ensuing review.

Signed-off-by: Sumera Priyadarsini <sylphrenadin@xxxxxxxxx>
---
Changes in V3:
- Refactor patchset(Melissa)
Changes in V2:
- Add atomic helper functions in a separate struct for virtual hardware
mode (Daniel)
- Remove spinlock across 'vkms_output->lock' in vkms_crtc.c(Daniel)
- Add vkms_composer_common() (Daniel)
---
 drivers/gpu/drm/vkms/vkms_crtc.c | 51 +++++++++++++++++++++++---------
 drivers/gpu/drm/vkms/vkms_drv.c  | 18 +++++++----
 drivers/gpu/drm/vkms/vkms_drv.h  |  1 +
 3 files changed, 51 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index 57bbd32e9beb..e6286f98d5b6 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -222,20 +222,20 @@ static int vkms_crtc_atomic_check(struct drm_crtc *crtc,
 	return 0;
 }
 
-static void vkms_crtc_atomic_enable(struct drm_crtc *crtc,
-				    struct drm_atomic_state *state)
+static void vkms_vblank_crtc_atomic_enable(struct drm_crtc *crtc,
+					   struct drm_atomic_state *state)
 {
 	drm_crtc_vblank_on(crtc);
 }
 
-static void vkms_crtc_atomic_disable(struct drm_crtc *crtc,
-				     struct drm_atomic_state *state)
+static void vkms_vblank_crtc_atomic_disable(struct drm_crtc *crtc,
+		struct drm_atomic_state *state)
 {
 	drm_crtc_vblank_off(crtc);
 }
 
-static void vkms_crtc_atomic_begin(struct drm_crtc *crtc,
-				   struct drm_atomic_state *state)
+static void vkms_vblank_crtc_atomic_begin(struct drm_crtc *crtc,
+		struct drm_atomic_state *state)
 {
 	struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
 
@@ -245,8 +245,8 @@ static void vkms_crtc_atomic_begin(struct drm_crtc *crtc,
 	spin_lock_irq(&vkms_output->lock);
 }
 
-static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
-				   struct drm_atomic_state *state)
+static void vkms_vblank_crtc_atomic_flush(struct drm_crtc *crtc,
+		struct drm_atomic_state *state)
 {
 	struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
 
@@ -268,18 +268,38 @@ static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
 	spin_unlock_irq(&vkms_output->lock);
 }
 
-static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
+/*
+ * Crtc functions for virtual hardware/vblankless mode
+ */
+static void vkms_virtual_crtc_atomic_flush(struct drm_crtc *crtc,
+		struct drm_atomic_state *state)
+{
+	struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
+	struct vkms_crtc_state *vkms_state = to_vkms_crtc_state(crtc->state);
+
+	vkms_crtc_composer(vkms_state);
+
+	vkms_output->composer_state = to_vkms_crtc_state(crtc->state);
+}
+
+static const struct drm_crtc_helper_funcs vkms_vblank_crtc_helper_funcs = {
 	.atomic_check	= vkms_crtc_atomic_check,
-	.atomic_begin	= vkms_crtc_atomic_begin,
-	.atomic_flush	= vkms_crtc_atomic_flush,
-	.atomic_enable	= vkms_crtc_atomic_enable,
-	.atomic_disable	= vkms_crtc_atomic_disable,
+	.atomic_begin	= vkms_vblank_crtc_atomic_begin,
+	.atomic_flush	= vkms_vblank_crtc_atomic_flush,
+	.atomic_enable	= vkms_vblank_crtc_atomic_enable,
+	.atomic_disable	= vkms_vblank_crtc_atomic_disable,
+};
+
+static const struct drm_crtc_helper_funcs vkms_virtual_crtc_helper_funcs = {
+	.atomic_check	= vkms_crtc_atomic_check,
+	.atomic_flush	= vkms_virtual_crtc_atomic_flush,
 };
 
 int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
 		   struct drm_plane *primary, struct drm_plane *cursor)
 {
 	struct vkms_output *vkms_out = drm_crtc_to_vkms_output(crtc);
+	struct vkms_device *vkmsdev = drm_device_to_vkms_device(dev);
 	int ret;
 
 	ret = drm_crtc_init_with_planes(dev, crtc, primary, cursor,
@@ -289,7 +309,10 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
 		return ret;
 	}
 
-	drm_crtc_helper_add(crtc, &vkms_crtc_helper_funcs);
+	if (vkmsdev->config->virtual_hw)
+		drm_crtc_helper_add(crtc, &vkms_virtual_crtc_helper_funcs);
+	else
+		drm_crtc_helper_add(crtc, &vkms_vblank_crtc_helper_funcs);
 
 	spin_lock_init(&vkms_out->lock);
 	spin_lock_init(&vkms_out->composer_lock);
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 2173b82606f6..945c4495d62a 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -44,6 +44,11 @@ static bool enable_writeback = true;
 module_param_named(enable_writeback, enable_writeback, bool, 0444);
 MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector support");
 
+static bool enable_virtual_hw = false;
+module_param_named(enable_virtual_hw, enable_virtual_hw, bool, 0444);
+MODULE_PARM_DESC(enable_virtual_hw, "Enable/Disable virtual hardware mode(virtual \
+hardware mode disables vblank interrupts)");
+
 DEFINE_DRM_GEM_FOPS(vkms_driver_fops);
 
 static void vkms_release(struct drm_device *dev)
@@ -159,12 +164,14 @@ static int vkms_create(struct vkms_config *config)
 		goto out_devres;
 	}
 
-	vkms_device->drm.irq_enabled = true;
+	vkms_device->drm.irq_enabled = !vkms_device->config->virtual_hw;
 
-	ret = drm_vblank_init(&vkms_device->drm, 1);
-	if (ret) {
-		DRM_ERROR("Failed to vblank\n");
-		goto out_devres;
+	if (!vkms_device->config->virtual_hw) {
+		ret = drm_vblank_init(&vkms_device->drm, 1);
+		if (ret) {
+			DRM_ERROR("Failed to vblank\n");
+			goto out_devres;
+		}
 	}
 
 	ret = vkms_modeset_init(vkms_device);
@@ -198,6 +205,7 @@ static int __init vkms_init(void)
 
 	config->cursor = enable_cursor;
 	config->writeback = enable_writeback;
+	config->virtual_hw = enable_virtual_hw;
 
 	return vkms_create(config);
 }
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 538315140585..a44f530ffaf0 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -85,6 +85,7 @@ struct vkms_device;
 struct vkms_config {
 	bool writeback;
 	bool cursor;
+	bool virtual_hw;
 	/* only set when instantiated */
 	struct vkms_device *dev;
 };
-- 
2.25.1