Re: [PATCH v4] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq_ctrl()

[Kuogee Hsieh]

On 5/11/2022 2:47 PM, Dmitry Baryshkov wrote:
> On 12/05/2022 00:40, Kuogee Hsieh wrote:
> > dp_catalog_ctrl_reset() will software reset DP controller. But it will
> > not reset programmable registers to default value. DP driver still have
> > to clear mask bits to interrupt status registers to disable interrupts
> > after software reset of controller. This patch removes the enable flag
> > condition checking to always clear mask bits of interrupt status
> > registers to disable interrupts if enable flag is false.
> >
> > This patch also will fix the potential problem happen at system 
> > suspend where
> > dp_ctrl_reset_irq_ctrl() was called to try to disable HPD related 
> > irqs but
> > the irq is still unmasked unexpectedly
>
> Why is it unmasked? Especially unexpectedly.

due to dp_catalog_ctrl_reset() does not clear hpd interrupt mask bits.

This is the problem this patch try to fix it.

I will revise commit text to explain more.

> > and can come in while system are
> > suspending. This leads to bus hangs if the irq is handled after we 
> > power down
> > the DP hardware because we run the irq handler and access a device 
> > register
> > assuming that no irq could ever come in if we powered down the 
> > device. We
> > don't know when the irq will be handled though, so it's possible the 
> > irq is
> > pending from before we disable the irq in the hardware.
>
> Please split into two patches.

this is just the same problem mention above.

> > Changes in v2:
> > -- add more details commit text
> >
> > Changes in v3:
> > -- add synchrons_irq()
> > -- add atomic_t suspended
> >
> > Changes in v4:
> > -- correct Fixes's commit ID
> >
> > Fixes: 989ebe7bc446 ("drm/msm/dp: do not initialize phy until plugin 
> > interrupt received")
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_ctrl.c    |  9 +++++++--
> >   drivers/gpu/drm/msm/dp/dp_display.c | 18 ++++++++++++++++++
> >   2 files changed, 25 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c 
> > b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > index af7a80c..f3e333e 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > @@ -1389,8 +1389,13 @@ void dp_ctrl_reset_irq_ctrl(struct dp_ctrl 
> > *dp_ctrl, bool enable)
> >         dp_catalog_ctrl_reset(ctrl->catalog);
> >   -    if (enable)
> > -        dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
> > +    /*
> > +     * all dp controller programmable registers will not
> > +     * be reset to default value after DP_SW_RESET
> > +     * therefore interrupt mask bits have to be updated
> > +     * to enable/disable interrupts
> > +     */
> > +    dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
> >   }
> >     void dp_ctrl_phy_init(struct dp_ctrl *dp_ctrl)
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
> > b/drivers/gpu/drm/msm/dp/dp_display.c
> > index c388323..c34dbfc 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -98,6 +98,8 @@ struct dp_display_private {
> >       struct dp_ctrl    *ctrl;
> >       struct dp_debug   *debug;
> >   +    atomic_t suspended;
>
> Usage of atomic_t signifies that something is wrong here. Bool should 
> be enough here.

suspended flag are shared by both event_thread and display_irq_handler, 
i think it need either atomic

or protected by spinlock.

> > +
> >       struct dp_usbpd_cb usbpd_cb;
> >       struct dp_display_mode dp_mode;
> >       struct msm_dp dp_display;
> > @@ -187,6 +189,11 @@ static int dp_add_event(struct 
> > dp_display_private *dp_priv, u32 event,
> >       int pndx;
> >         spin_lock_irqsave(&dp_priv->event_lock, flag);
> > +    if (atomic_read(&dp_priv->suspended)) {
> > +        spin_unlock_irqrestore(&dp_priv->event_lock, flag);
> > +        return -EPERM;
>
> Why EPERM?
>
> > +    }
> > +
> >       pndx = dp_priv->event_pndx + 1;
> >       pndx %= DP_EVENT_Q_MAX;
> >       if (pndx == dp_priv->event_gndx) {
> > @@ -454,6 +461,13 @@ static void dp_display_host_deinit(struct 
> > dp_display_private *dp)
> >           dp->dp_display.connector_type, dp->core_initialized,
> >           dp->phy_initialized);
> >   +    if (!dp->core_initialized) {
>
> Can this happen?

not likely,

but It should not in this patch. will double check.

> > +        DRM_DEBUG_DP("DP core not initialized\n");
> > +        return;
> > +    }
> > +
> > +    synchronize_irq(dp->irq);
>
> Why? If you need to run with IRQs disabled, you can use 
> suspend_late/early_resume. But generally it should be enough to check 
> for the !suspended in the IRQ.
>
> > +
> >       dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
> >       dp_aux_deinit(dp->aux);
> >       dp_power_deinit(dp->power);
> > @@ -1362,6 +1376,8 @@ static int dp_pm_resume(struct device *dev)
> >           dp->dp_display.connector_type, dp->core_initialized,
> >           dp->phy_initialized, dp_display->power_on);
> >   +    atomic_set(&dp->suspended, 0);
> > +
> >       /* start from disconnected state */
> >       dp->hpd_state = ST_DISCONNECTED;
> >   @@ -1431,6 +1447,8 @@ static int dp_pm_suspend(struct device *dev)
> >           dp->dp_display.connector_type, dp->core_initialized,
> >           dp->phy_initialized, dp_display->power_on);
> >   +    atomic_inc(&dp->suspended);
> > +
> >       /* mainlink enabled */
> >       if (dp_power_clk_status(dp->power, DP_CTRL_PM))
> >           dp_ctrl_off_link_stream(dp->ctrl);