[PATCH 05/14] drm/imx: dc-crtc: Disable at boot

Liu Ying
2025-07-04T10:37:37Z

CRTC(s) could still be running after the DRM device is unplugged by
calling drm_dev_unplug(), because the CRTC disablement logic is
protected and bypassed by the drm_dev_enter()/drm_dev_exit() pair.
Hence, Pixel Engine's AXI clock use count(managed by Pixel Engine
driver's runtime PM) and pixel clock use count could be inbalanced
after removing and re-installing the driver module. To fix this,
add a helper dc_crtc_disable_at_boot() and call it to properly
disable all CRTCs before advertising DRM device to user-space by
calling drm_dev_register().

Fixes: 711a3b878366 ("drm/imx: Add i.MX8qxp Display Controller KMS")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
drivers/gpu/drm/imx/dc/dc-crtc.c | 50 ++++++++++++++++++++++++++++++++++++----
drivers/gpu/drm/imx/dc/dc-drv.c | 5 ++++
drivers/gpu/drm/imx/dc/dc-drv.h | 3 +++
3 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/imx/dc/dc-crtc.c b/drivers/gpu/drm/imx/dc/dc-crtc.c
index 31d3a982deaf7a0390937285c9d5d00100323181..45a87df1ad6a8bd768aa5ed38d6f03f14052b3d7 100644
--- a/drivers/gpu/drm/imx/dc/dc-crtc.c
+++ b/drivers/gpu/drm/imx/dc/dc-crtc.c
@@ -293,6 +293,16 @@ dc_crtc_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *state)
dc_crtc_queue_state_event(new_crtc_state);
}

+static inline void __dc_crtc_disable_fg(struct drm_crtc *crtc)
+{
+ struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
+
+ enable_irq(dc_crtc->irq_dec_seqcomplete);
+ dc_fg_disable(dc_crtc->fg);
+ DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(dec_seqcomplete_done);
+ disable_irq(dc_crtc->irq_dec_seqcomplete);
+}
+
static void
dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *state)
{
@@ -305,11 +315,7 @@ dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *state)
if (!drm_dev_enter(crtc->dev, &idx))
goto out;

- enable_irq(dc_crtc->irq_dec_seqcomplete);
- dc_fg_disable(dc_crtc->fg);
- DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(dec_seqcomplete_done);
- disable_irq(dc_crtc->irq_dec_seqcomplete);
-
+ __dc_crtc_disable_fg(crtc);
dc_fg_disable_clock(dc_crtc->fg);

/* request pixel engine power-off as plane is off too */
@@ -337,6 +343,40 @@ dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *state)
spin_unlock_irq(&crtc->dev->event_lock);
}

+void dc_crtc_disable_at_boot(struct drm_crtc *crtc)
+{
+ struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev);
+ struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
+ int ret;
+
+ ret = pm_runtime_resume_and_get(dc_crtc->de->dev);
+ if (ret < 0) {
+ dc_crtc_err(crtc, "failed to get DC display engine RPM: %d\n",
+ ret);
+ return;
+ }
+
+ if (!dc_fg_wait_for_frame_index_moving(dc_crtc->fg)) {
+ dc_crtc_dbg(crtc, "FrameGen frame index isn't moving\n");
+ goto out;
+ }
+
+ dc_crtc_dbg(crtc, "disabling at boot\n");
+ __dc_crtc_disable_fg(crtc);
+ dc_fg_disable_clock(dc_crtc->fg);
+
+ if (!dc_drm->pe_clk_axi_disabled) {
+ clk_disable_unprepare(dc_drm->pe->clk_axi);
+ dc_drm->pe_clk_axi_disabled = true;
+ }
+
+out:
+ ret = pm_runtime_put(dc_crtc->de->dev);
+ if (ret < 0)
+ dc_crtc_err(crtc, "failed to put DC display engine RPM: %d\n",
+ ret);
+}
+
static bool dc_crtc_get_scanout_position(struct drm_crtc *crtc,
bool in_vblank_irq,
int *vpos, int *hpos,
diff --git a/drivers/gpu/drm/imx/dc/dc-drv.c b/drivers/gpu/drm/imx/dc/dc-drv.c
index 04f021d2d6cfc93972aa8d9073be24d347152602..f93766b6bfbfae8510db05278d104820ca0719c4 100644
--- a/drivers/gpu/drm/imx/dc/dc-drv.c
+++ b/drivers/gpu/drm/imx/dc/dc-drv.c
@@ -17,6 +17,7 @@

#include <drm/clients/drm_client_setup.h>
#include <drm/drm_atomic_helper.h>
+#include <drm/drm_crtc.h>
#include <drm/drm_drv.h>
#include <drm/drm_fbdev_dma.h>
#include <drm/drm_fourcc.h>
@@ -96,6 +97,7 @@ static int dc_drm_bind(struct device *dev)
struct dc_priv *priv = dev_get_drvdata(dev);
struct dc_drm_device *dc_drm;
struct drm_device *drm;
+ struct drm_crtc *crtc;
int ret;

dc_drm = devm_drm_dev_alloc(dev, &dc_drm_driver, struct dc_drm_device,
@@ -118,6 +120,9 @@ static int dc_drm_bind(struct device *dev)
if (ret)
return ret;

+ drm_for_each_crtc(crtc, drm)
+ dc_crtc_disable_at_boot(crtc);
+
ret = drm_dev_register(drm, 0);
if (ret) {
dev_err(dev, "failed to register drm device: %d\n", ret);
diff --git a/drivers/gpu/drm/imx/dc/dc-drv.h b/drivers/gpu/drm/imx/dc/dc-drv.h
index eb61b8c7626933adc7688f046139e2167665dad1..68e99ba7cedbca1b8bdc0d8ced7a610a1056bfc7 100644
--- a/drivers/gpu/drm/imx/dc/dc-drv.h
+++ b/drivers/gpu/drm/imx/dc/dc-drv.h
@@ -50,6 +50,8 @@ struct dc_drm_device {
struct dc_pe *pe;
/** @tc: tcon list */
struct dc_tc *tc[DC_DISPLAYS];
+ /** @pe_clk_axi_disabled: disablement flag at boot */
+ bool pe_clk_axi_disabled;
};

struct dc_subdev_info {
@@ -96,6 +98,7 @@ static inline int dc_subdev_get_id(const struct dc_subdev_info *info,
return -EINVAL;
}

+void dc_crtc_disable_at_boot(struct drm_crtc *crtc);
void dc_de_post_bind(struct dc_drm_device *dc_drm);
void dc_pe_post_bind(struct dc_drm_device *dc_drm);

--
2.34.1