drm/msm/hdmi: Remove spurious IRQF_ONESHOT flag

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@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20220201174734.196718-3-daniel.thompson@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

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",