Re: [PATCH v6 04/13] drm/imx: dc-crtc: Disable at boot
From: Maxime Ripard <mripard@kernel.org>
Date: 2026-09-04 08:27:47
Also in:
dri-devel, imx, linux-devicetree, lkml
Hi, On Fri, Sep 04, 2026 at 03:54:54PM +0800, Liu Ying wrote:
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")
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Liu Ying <victor.liu@nxp.com>Just as a heads-up, the readout series I'm working on is probably going to help you deal with it: https://lore.kernel.org/r/20260629-drm-state-readout-v4-0-5966657980ed@kernel.org (local)
quoted hunk ↗ jump to hunk
--- v6: - Rebase onto the latest drm-misc-next and resolve conflicts. v3: - Collect Frank's R-b tag. --- drivers/gpu/drm/imx/dc/dc-crtc.c | 55 +++++++++++++++++++++++++++++++++------- drivers/gpu/drm/imx/dc/dc-drv.c | 5 ++++ drivers/gpu/drm/imx/dc/dc-drv.h | 3 +++ 3 files changed, 54 insertions(+), 9 deletions(-)diff --git a/drivers/gpu/drm/imx/dc/dc-crtc.c b/drivers/gpu/drm/imx/dc/dc-crtc.c index 0d64186a9901..1a537cf88daf 100644 --- a/drivers/gpu/drm/imx/dc/dc-crtc.c +++ b/drivers/gpu/drm/imx/dc/dc-crtc.c@@ -293,23 +293,29 @@ dc_crtc_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_commit *state) dc_crtc_queue_state_event(new_crtc_state); } -static void -dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_commit *state) +static inline void __dc_crtc_disable_fg(struct drm_crtc *crtc) { - struct drm_crtc_state *new_crtc_state = - drm_atomic_get_new_crtc_state(state, crtc); - struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev); struct dc_crtc *dc_crtc = to_dc_crtc(crtc); - int idx; - - 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); +} +static void +dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_commit *state) +{ + struct drm_crtc_state *new_crtc_state = + drm_atomic_get_new_crtc_state(state, crtc); + struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev); + struct dc_crtc *dc_crtc = to_dc_crtc(crtc); + int idx; + + if (!drm_dev_enter(crtc->dev, &idx)) + goto out; + + __dc_crtc_disable_fg(crtc); dc_fg_disable_clock(dc_crtc->fg); /* request pixel engine power-off as plane is off too */@@ -331,6 +337,37 @@ dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_commit *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: + pm_runtime_put(dc_crtc->de->dev);
I'm not sure you actually need the pe_clk_axi_disabled flag. If you make it handled by runtime_pm, then you can also use pm_runtime_set_active to flag the device as active already when you probe, and the runtime_pm will know when to enable / disable things properly. Maxime
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