| Message ID | 20220201174734.196718-2-daniel.thompson@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| 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 (and for "normal" kernels > it is a nop). In this case I can find no evidence that suppressing forced > threading is intentional. Had it been intentional then a driver must adopt > the raw_spinlock API in order to avoid deadlocks on PREEMPT_RT kernels > (and avoid calling any kernel API that uses regular spinlocks). > > Fix this by removing the spurious additional flag. > > This change is required for my Snapdragon 7cx Gen2 tablet to boot-to-GUI > with PREEMPT_RT enabled. > > Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > --- > drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c > index 6b3ced4aaaf5d..3a3f53f0c8ae1 100644 > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c > @@ -1877,7 +1877,7 @@ int msm_dsi_host_init(struct msm_dsi *msm_dsi) > > /* do not autoenable, will be enabled later */ > ret = devm_request_irq(&pdev->dev, msm_host->irq, dsi_host_irq, > - IRQF_TRIGGER_HIGH | IRQF_ONESHOT | IRQF_NO_AUTOEN, > + IRQF_TRIGGER_HIGH | IRQF_NO_AUTOEN, > "dsi_isr", msm_host); > if (ret < 0) { > dev_err(&pdev->dev, "failed to request IRQ%u: %d\n",
diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c index 6b3ced4aaaf5d..3a3f53f0c8ae1 100644 --- a/drivers/gpu/drm/msm/dsi/dsi_host.c +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c @@ -1877,7 +1877,7 @@ int msm_dsi_host_init(struct msm_dsi *msm_dsi) /* do not autoenable, will be enabled later */ ret = devm_request_irq(&pdev->dev, msm_host->irq, dsi_host_irq, - IRQF_TRIGGER_HIGH | IRQF_ONESHOT | IRQF_NO_AUTOEN, + IRQF_TRIGGER_HIGH | IRQF_NO_AUTOEN, "dsi_isr", msm_host); if (ret < 0) { dev_err(&pdev->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 (and for "normal" kernels it is a nop). In this case I can find no evidence that suppressing forced threading is intentional. Had it been intentional then a driver must adopt the raw_spinlock API in order to avoid deadlocks on PREEMPT_RT kernels (and avoid calling any kernel API that uses regular spinlocks). Fix this by removing the spurious additional flag. This change is required for my Snapdragon 7cx Gen2 tablet to boot-to-GUI with PREEMPT_RT enabled. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> --- drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)