On 01/02/2022 20:47, Daniel Thompson wrote:
Quoting the header comments, IRQF_ONESHOT is "Used by threaded interrupts
which need to keep the irq line disabled until the threaded handler has
been run.". When applied to an interrupt that doesn't request a threaded
irq then IRQF_ONESHOT has a lesser known (undocumented?) side effect,
which it to disable the forced threading of irqs. For "normal" kernels
if there is no thread_fn then IRQF_ONESHOT is a nop.
In this case disabling forced threading is not appropriate because the
driver calls wake_up_all() (via msm_hdmi_i2c_irq) and also directly uses
the regular spinlock API for locking (in msm_hdmi_hdcp_irq() ). Neither
of these APIs can be called from no-thread interrupt handlers on
PREEMPT_RT systems.
Fix this by removing IRQF_ONESHOT.
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
drivers/gpu/drm/msm/hdmi/hdmi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/hdmi/hdmi.c b/drivers/gpu/drm/msm/hdmi/hdmi.c
index 719720709e9e7..e167817b42958 100644
--- a/drivers/gpu/drm/msm/hdmi/hdmi.c
+++ b/drivers/gpu/drm/msm/hdmi/hdmi.c
@@ -306,7 +306,7 @@ int msm_hdmi_modeset_init(struct hdmi *hdmi,
}
ret = devm_request_irq(&pdev->dev, hdmi->irq,
- msm_hdmi_irq, IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+ msm_hdmi_irq, IRQF_TRIGGER_HIGH,
"hdmi_isr", hdmi);
if (ret < 0) {
DRM_DEV_ERROR(dev->dev, "failed to request IRQ%u: %d\n",
--
With best wishes
Dmitry
