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Date: Wed, 11 May 2022 16:21:54 -0700
From: Kuogee Hsieh <quic_khsieh@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
<robdclark@...il.com>, <sean@...rly.run>, <swboyd@...omium.org>,
<dianders@...omium.org>, <vkoul@...nel.org>, <daniel@...ll.ch>,
<airlied@...ux.ie>, <agross@...nel.org>,
<bjorn.andersson@...aro.org>
CC: <quic_abhinavk@...cinc.com>, <quic_aravindh@...cinc.com>,
<quic_sbillaka@...cinc.com>, <freedreno@...ts.freedesktop.org>,
<dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] drm/msm/dp: Always clear mask bits to disable
interrupts at dp_ctrl_reset_irq_ctrl()
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@...cinc.com>
>> ---
>> 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);
>
>
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