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Message-ID: <5c49a2d2-2c67-502c-ca1a-5c3acddd5797@quicinc.com>
Date: Mon, 30 Jan 2023 09:58:51 -0800
From: Kuogee Hsieh <quic_khsieh@...cinc.com>
To: Douglas Anderson <dianders@...omium.org>,
Rob Clark <robdclark@...il.com>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Stephen Boyd <swboyd@...omium.org>,
Alex Deucher <alexander.deucher@....com>,
Bjorn Andersson <quic_bjorande@...cinc.com>,
Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...il.com>,
"Javier Martinez Canillas" <javierm@...hat.com>,
Johan Hovold <johan+linaro@...nel.org>,
Lyude Paul <lyude@...hat.com>,
"Sankeerth Billakanti" <quic_sbillaka@...cinc.com>,
Sean Paul <sean@...rly.run>,
"Thomas Zimmermann" <tzimmermann@...e.de>,
<dri-devel@...ts.freedesktop.org>,
<freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] drm/msm/dp: Return IRQ_NONE for unhandled
interrupts
On 1/26/2023 5:09 PM, Douglas Anderson wrote:
> If our interrupt handler gets called and we don't really handle the
> interrupt then we should return IRQ_NONE. The current interrupt
> handler didn't do this, so let's fix it.
>
> NOTE: for some of the cases it's clear that we should return IRQ_NONE
> and some cases it's clear that we should return IRQ_HANDLED. However,
> there are a few that fall somewhere in between. Specifically, the
> documentation for when to return IRQ_NONE vs. IRQ_HANDLED is probably
> best spelled out in the commit message of commit d9e4ad5badf4
> ("Document that IRQ_NONE should be returned when IRQ not actually
> handled"). That commit makes it clear that we should return
> IRQ_HANDLED if we've done something to make the interrupt stop
> happening.
>
> The case where it's unclear is, for instance, in dp_aux_isr() after
> we've read the interrupt using dp_catalog_aux_get_irq() and confirmed
> that "isr" is non-zero. The function dp_catalog_aux_get_irq() not only
> reads the interrupts but it also "ack"s all the interrupts that are
> returned. For an "unknown" interrupt this has a very good chance of
> actually stopping the interrupt from happening. That would mean we've
> identified that it's our device and done something to stop them from
> happening and should return IRQ_HANDLED. Specifically, it should be
> noted that most interrupts that need "ack"ing are ones that are
> one-time events and doing an "ack" is enough to clear them. However,
> since these interrupts are unknown then, by definition, it's unknown
> if "ack"ing them is truly enough to clear them. It's possible that we
> also need to remove the original source of the interrupt. In this
> case, IRQ_NONE would be a better choice.
>
> Given that returning an occasional IRQ_NONE isn't the absolute end of
> the world, however, let's choose that course of action. The IRQ
> framework will forgive a few IRQ_NONE returns now and again (and it
> won't even log them, which is why we have to log them ourselves). This
> means that if we _do_ end hitting an interrupt where "ack"ing isn't
> enough the kernel will eventually detect the problem and shut our
> device down.
>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
Tested-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>
> (no changes since v1)
>
> drivers/gpu/drm/msm/dp/dp_aux.c | 12 +++++++-----
> drivers/gpu/drm/msm/dp/dp_aux.h | 2 +-
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 10 ++++++++--
> drivers/gpu/drm/msm/dp/dp_ctrl.h | 2 +-
> drivers/gpu/drm/msm/dp/dp_display.c | 8 +++++---
> 5 files changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c
> index 84f9e3e5f964..8e3b677f35e6 100644
> --- a/drivers/gpu/drm/msm/dp/dp_aux.c
> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
> @@ -368,14 +368,14 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
> return ret;
> }
>
> -void dp_aux_isr(struct drm_dp_aux *dp_aux)
> +irqreturn_t dp_aux_isr(struct drm_dp_aux *dp_aux)
> {
> u32 isr;
> struct dp_aux_private *aux;
>
> if (!dp_aux) {
> DRM_ERROR("invalid input\n");
> - return;
> + return IRQ_NONE;
> }
>
> aux = container_of(dp_aux, struct dp_aux_private, dp_aux);
> @@ -384,11 +384,11 @@ void dp_aux_isr(struct drm_dp_aux *dp_aux)
>
> /* no interrupts pending, return immediately */
> if (!isr)
> - return;
> + return IRQ_NONE;
>
> if (!aux->cmd_busy) {
> DRM_ERROR("Unexpected DP AUX IRQ %#010x when not busy\n", isr);
> - return;
> + return IRQ_NONE;
> }
>
> /*
> @@ -420,10 +420,12 @@ void dp_aux_isr(struct drm_dp_aux *dp_aux)
> aux->aux_error_num = DP_AUX_ERR_NONE;
> } else {
> DRM_WARN("Unexpected interrupt: %#010x\n", isr);
> - return;
> + return IRQ_NONE;
> }
>
> complete(&aux->comp);
> +
> + return IRQ_HANDLED;
> }
>
> void dp_aux_reconfig(struct drm_dp_aux *dp_aux)
> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.h b/drivers/gpu/drm/msm/dp/dp_aux.h
> index e930974bcb5b..511305da4f66 100644
> --- a/drivers/gpu/drm/msm/dp/dp_aux.h
> +++ b/drivers/gpu/drm/msm/dp/dp_aux.h
> @@ -11,7 +11,7 @@
>
> int dp_aux_register(struct drm_dp_aux *dp_aux);
> void dp_aux_unregister(struct drm_dp_aux *dp_aux);
> -void dp_aux_isr(struct drm_dp_aux *dp_aux);
> +irqreturn_t dp_aux_isr(struct drm_dp_aux *dp_aux);
> void dp_aux_init(struct drm_dp_aux *dp_aux);
> void dp_aux_deinit(struct drm_dp_aux *dp_aux);
> void dp_aux_reconfig(struct drm_dp_aux *dp_aux);
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index dd26ca651a05..1a5377ef1967 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1979,27 +1979,33 @@ int dp_ctrl_off(struct dp_ctrl *dp_ctrl)
> return ret;
> }
>
> -void dp_ctrl_isr(struct dp_ctrl *dp_ctrl)
> +irqreturn_t dp_ctrl_isr(struct dp_ctrl *dp_ctrl)
> {
> struct dp_ctrl_private *ctrl;
> u32 isr;
> + irqreturn_t ret = IRQ_NONE;
>
> if (!dp_ctrl)
> - return;
> + return IRQ_NONE;
>
> ctrl = container_of(dp_ctrl, struct dp_ctrl_private, dp_ctrl);
>
> isr = dp_catalog_ctrl_get_interrupt(ctrl->catalog);
>
> +
> if (isr & DP_CTRL_INTR_READY_FOR_VIDEO) {
> drm_dbg_dp(ctrl->drm_dev, "dp_video_ready\n");
> complete(&ctrl->video_comp);
> + ret = IRQ_HANDLED;
> }
>
> if (isr & DP_CTRL_INTR_IDLE_PATTERN_SENT) {
> drm_dbg_dp(ctrl->drm_dev, "idle_patterns_sent\n");
> complete(&ctrl->idle_comp);
> + ret = IRQ_HANDLED;
> }
> +
> + return ret;
> }
>
> struct dp_ctrl *dp_ctrl_get(struct device *dev, struct dp_link *link,
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> index 9f29734af81c..c3af06dc87b1 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.h
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> @@ -25,7 +25,7 @@ int dp_ctrl_off_link_stream(struct dp_ctrl *dp_ctrl);
> int dp_ctrl_off_link(struct dp_ctrl *dp_ctrl);
> int dp_ctrl_off(struct dp_ctrl *dp_ctrl);
> void dp_ctrl_push_idle(struct dp_ctrl *dp_ctrl);
> -void dp_ctrl_isr(struct dp_ctrl *dp_ctrl);
> +irqreturn_t dp_ctrl_isr(struct dp_ctrl *dp_ctrl);
> void dp_ctrl_handle_sink_request(struct dp_ctrl *dp_ctrl);
> struct dp_ctrl *dp_ctrl_get(struct device *dev, struct dp_link *link,
> struct dp_panel *panel, struct drm_dp_aux *aux,
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index bde1a7ce442f..b5343c9f1c1e 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1204,7 +1204,7 @@ static int dp_hpd_event_thread_start(struct dp_display_private *dp_priv)
> static irqreturn_t dp_display_irq_handler(int irq, void *dev_id)
> {
> struct dp_display_private *dp = dev_id;
> - irqreturn_t ret = IRQ_HANDLED;
> + irqreturn_t ret = IRQ_NONE;
> u32 hpd_isr_status;
>
> if (!dp) {
> @@ -1232,13 +1232,15 @@ static irqreturn_t dp_display_irq_handler(int irq, void *dev_id)
>
> if (hpd_isr_status & DP_DP_HPD_UNPLUG_INT_MASK)
> dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> +
> + ret = IRQ_HANDLED;
> }
>
> /* DP controller isr */
> - dp_ctrl_isr(dp->ctrl);
> + ret |= dp_ctrl_isr(dp->ctrl);
>
> /* DP aux isr */
> - dp_aux_isr(dp->aux);
> + ret |= dp_aux_isr(dp->aux);
>
> return ret;
> }
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