On 2025-06-27 04:06, Inki Dae wrote:

Hi,

2025년 6월 27일 (금) 오전 4:21, Kaustabh Chakraborty kauschluss@disroot.org님이 작성:

...

decon_commit() has a condition guard at the beginning:

    if (ctx->suspended)
            return;

But, when it is being called from decon_atomic_enable(), ctx->suspended is still set to true, which prevents its execution. decon_commit() is vital for setting up display timing values, without which the display pipeline fails to function properly. Call the function after ctx->suspended is set to false as a fix.

Good observation. However, I think a more generic solution is needed.

...

Cc: stable@vger.kernel.org Fixes: 96976c3d9aff ("drm/exynos: Add DECON driver") Signed-off-by: Kaustabh Chakraborty kauschluss@disroot.org

---

drivers/gpu/drm/exynos/exynos7_drm_decon.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos7_drm_decon.c b/drivers/gpu/drm/exynos/exynos7_drm_decon.c index f91daefa9d2bc5e314c279822047e60ee0d7ca99..43bcbe2e2917df43d7c2d27a9771e892628dd682 100644 --- a/drivers/gpu/drm/exynos/exynos7_drm_decon.c +++ b/drivers/gpu/drm/exynos/exynos7_drm_decon.c @@ -583,9 +583,9 @@ static void decon_atomic_enable(struct exynos_drm_crtc *crtc) if (test_and_clear_bit(0, &ctx->irq_flags)) decon_enable_vblank(ctx->crtc);

•   decon_commit(ctx->crtc);
  

•   ctx->suspended = false;
  

•   decon_commit(ctx->crtc);
  

There seem to be three possible solutions:

1. Remove all code related to ctx->suspended. If the pipeline flow is

properly managed as in the exynos5433_drm_decon.c module, checking the ctx->suspended state may no longer be necessary. 2. Remove the ctx->suspended check from decon_commit(). Since the runtime PM resume is already called before decon_commit() in decon_atomic_enable(), the DECON controller should already be enabled at the hardware level, and decon_commit() should work correctly. 3. Move the code that updates ctx->suspended from decon_atomic_enable() and decon_atomic_disable() to exynos7_decon_resume() and exynos7_decon_suspend(), respectively. The decon_atomic_enable() function calls pm_runtime_resume_and_get(), which ultimately triggers exynos7_decon_resume(). It would be more appropriate to set ctx->suspended = false in the exynos7_decon_resume() function, as this is the standard place to handle hardware state changes and resume actions. decon_atomic_enable() is responsible for requesting enablement of the DECON controller, but actual hardware state transitions will be handled within exynos7_decon_resume() and exynos7_decon_suspend().

Unfortunately, I do not have hardware to test this patch myself. Would it be possible for you to try one of these approaches and verify the behavior? Option 1 would be the best solution if feasible.

Yes, it works fine indeed. Thanks!

Thanks, Inki Dae

...

}

static void decon_atomic_disable(struct exynos_drm_crtc *crtc)

-- 2.49.0

2025년 6월 27일 (금) 오전 4:21, Kaustabh Chakraborty kauschluss@disroot.org님이 작성:

If there's support for another console device (such as a TTY serial), the kernel occasionally panics during boot. The panic message and a relevant snippet of the call stack is as follows:

Unable to handle kernel NULL pointer dereference at virtual address 000000000000000 Call trace: drm_crtc_handle_vblank+0x10/0x30 (P) decon_irq_handler+0x88/0xb4 [...]

It seems that if the display is already enabled by the bootloader during the boot process, a vblank interrupt may be triggered before the initialization of drm_dev is complete. This could be the root cause of the issue.

Applied.

Thanks, Inki Dae

Otherwise, the panics don't happen. This indicates that it's some sort of race condition.

Add a check to validate if the drm device can handle vblanks before calling drm_crtc_handle_vblank() to avoid this.

Cc: stable@vger.kernel.org Fixes: 96976c3d9aff ("drm/exynos: Add DECON driver") Signed-off-by: Kaustabh Chakraborty kauschluss@disroot.org

---

drivers/gpu/drm/exynos/exynos7_drm_decon.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/exynos/exynos7_drm_decon.c b/drivers/gpu/drm/exynos/exynos7_drm_decon.c index 43bcbe2e2917df43d7c2d27a9771e892628dd682..c0c0f23169c993ac315fc8d7bcbd09ea6ec9966a 100644 --- a/drivers/gpu/drm/exynos/exynos7_drm_decon.c +++ b/drivers/gpu/drm/exynos/exynos7_drm_decon.c @@ -636,6 +636,10 @@ static irqreturn_t decon_irq_handler(int irq, void *dev_id) if (!ctx->drm_dev) goto out;

•   /* check if crtc and vblank have been initialized properly */
  

•   if (!drm_dev_has_vblank(ctx->drm_dev))
  

•           goto out;
  

•   if (!ctx->i80_if) {
            drm_crtc_handle_vblank(&ctx->crtc->base);
  
  
  

-- 2.49.0