Before updating the display from the console's shadow buffer, the dirty
worker now waits for a vblank. This allows several screen updates to pile
up and acts as a rate limiter. If a DRM master is present, it could
interfere with the vblank. Don't wait in this case.
v4:
* share code with WAITFORVSYNC ioctl (Emil)
* use lock guard
v3:
* add back helper->lock
* acquire DRM master status while waiting for vblank
v2:
* don't hold helper->lock while waiting for vblank
Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
Acked-by: Sam Ravnborg <s...@ravnborg.org>
---
The previous reviews of this patch can be found as part of the series at
https://patchwork.freedesktop.org/series/66442/#rev3 .
---
drivers/gpu/drm/drm_client_modeset.c | 44 ++++++++++++++++++++++++++++
drivers/gpu/drm/drm_fb_helper.c | 30 ++++---------------
include/drm/drm_client.h | 1 +
3 files changed, 51 insertions(+), 24 deletions(-)
diff --git a/drivers/gpu/drm/drm_client_modeset.c
b/drivers/gpu/drm/drm_client_modeset.c
index 9c2c3b0c8c47..fc4caf7da5fc 100644
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -1293,6 +1293,50 @@ int drm_client_modeset_dpms(struct drm_client_dev
*client, int mode)
}
EXPORT_SYMBOL(drm_client_modeset_dpms);
+/**
+ * drm_client_modeset_wait_for_vblank() - Wait for the next VBLANK to occur
+ * @client: DRM client
+ * @crtc_index: The ndex of the CRTC to wait on
+ *
+ * Block the caller until the given CRTC has seen a VBLANK. Do nothing
+ * if the CRTC is disabled. If there's another DRM master present, fail
+ * with -EBUSY.
+ *
+ * Returns:
+ * 0 on success, or negative error code otherwise.
+ */
+int drm_client_modeset_wait_for_vblank(struct drm_client_dev *client, unsigned
int crtc_index)
+{
+ struct drm_device *dev = client->dev;
+ struct drm_crtc *crtc;
+ int ret;
+
+ /*
+ * Rate-limit update frequency to vblank. If there's a DRM master
+ * present, it could interfere while we're waiting for the vblank
+ * event. Don't wait in this case.
+ */
+ if (!drm_master_internal_acquire(dev))
+ return -EBUSY;
+
+ crtc = client->modesets[crtc_index].crtc;
+
+ /*
+ * Only wait for a vblank event if the CRTC is enabled, otherwise
+ * just don't do anything, not even report an error.
+ */
+ ret = drm_crtc_vblank_get(crtc);
+ if (!ret) {
+ drm_crtc_wait_one_vblank(crtc);
+ drm_crtc_vblank_put(crtc);
+ }
+
+ drm_master_internal_release(dev);
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_client_modeset_wait_for_vblank);
+
#ifdef CONFIG_DRM_KUNIT_TEST
#include "tests/drm_client_modeset_test.c"
#endif
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 11a5b60cb9ce..53e9dc0543de 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -368,6 +368,10 @@ static void drm_fb_helper_fb_dirty(struct drm_fb_helper
*helper)
unsigned long flags;
int ret;
+ mutex_lock(&helper->lock);
+ drm_client_modeset_wait_for_vblank(&helper->client, 0);
+ mutex_unlock(&helper->lock);
+
if (drm_WARN_ON_ONCE(dev, !helper->funcs->fb_dirty))
return;
@@ -1068,15 +1072,9 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned
int cmd,
unsigned long arg)
{
struct drm_fb_helper *fb_helper = info->par;
- struct drm_device *dev = fb_helper->dev;
- struct drm_crtc *crtc;
int ret = 0;
- mutex_lock(&fb_helper->lock);
- if (!drm_master_internal_acquire(dev)) {
- ret = -EBUSY;
- goto unlock;
- }
+ guard(mutex)(&fb_helper->lock);
switch (cmd) {
case FBIO_WAITFORVSYNC:
@@ -1096,28 +1094,12 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned
int cmd,
* make. If we're not smart enough here, one should
* just consider switch the userspace to KMS.
*/
- crtc = fb_helper->client.modesets[0].crtc;
-
- /*
- * Only wait for a vblank event if the CRTC is
- * enabled, otherwise just don't do anythintg,
- * not even report an error.
- */
- ret = drm_crtc_vblank_get(crtc);
- if (!ret) {
- drm_crtc_wait_one_vblank(crtc);
- drm_crtc_vblank_put(crtc);
- }
-
- ret = 0;
+ ret = drm_client_modeset_wait_for_vblank(&fb_helper->client, 0);
break;
default:
ret = -ENOTTY;
}
- drm_master_internal_release(dev);
-unlock:
- mutex_unlock(&fb_helper->lock);
return ret;
}
EXPORT_SYMBOL(drm_fb_helper_ioctl);
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 146ca80e35db..bdd845e383ef 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -220,6 +220,7 @@ int drm_client_modeset_check(struct drm_client_dev *client);
int drm_client_modeset_commit_locked(struct drm_client_dev *client);
int drm_client_modeset_commit(struct drm_client_dev *client);
int drm_client_modeset_dpms(struct drm_client_dev *client, int mode);
+int drm_client_modeset_wait_for_vblank(struct drm_client_dev *client, unsigned
int crtc_index);
/**
* drm_client_for_each_modeset() - Iterate over client modesets
--
2.50.1
