| Message ID | 20220201174734.196718-3-daniel.thompson@linaro.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | drm/msm: Remove spurious IRQF_ONESHOT flags from dsi & hdmi | expand |
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@linaro.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > --- > 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",
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",
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> --- drivers/gpu/drm/msm/hdmi/hdmi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)