linux-kernel - Re: [PATCH v3] drm/msm/dp: check core_initialized flag at both host_init() and host

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Date:   Wed, 1 Mar 2023 23:15:22 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        dianders@...omium.org, vkoul@...nel.org, daniel@...ll.ch,
        airlied@...il.com, agross@...nel.org, andersson@...nel.org,
        quic_abhinavk@...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 v3] drm/msm/dp: check core_initialized flag at both
 host_init() and host_deinit()

On 01/03/2023 18:57, Kuogee Hsieh wrote:
> 
> On 2/28/2023 6:16 PM, Dmitry Baryshkov wrote:
>> On Wed, 1 Mar 2023 at 02:17, Kuogee Hsieh <quic_khsieh@...cinc.com> 
>> wrote:
>>> There is a reboot/suspend test case where system suspend is forced
>>> during system booting up. Since dp_display_host_init() of external
>>> DP is executed at hpd thread context, this test case may created a
>>> scenario that dp_display_host_deinit() from pm_suspend() run before
>>> dp_display_host_init() if hpd thread has no chance to run during
>>> booting up while suspend request command was issued. At this scenario
>>> system will crash at aux register access at dp_display_host_deinit()
>>> since aux clock had not yet been enabled by dp_display_host_init().
>>> Therefore we have to ensure aux clock enabled by checking
>>> core_initialized flag before access aux registers at pm_suspend.
>> Can a call to dp_display_host_init() be moved from
>> dp_display_config_hpd() to dp_display_bind()?
> 
> yes,  Sankeerth's  "drm/msm/dp: enable pm_runtime support for dp driver" 
> patch is doing that which is under review.
> 
> https://patchwork.freedesktop.org/patch/523879/?series=114297&rev=1

No, he is doing another thing. He is moving these calls to pm_runtime 
callbacks, not to the dp_display_bind().

>> Related question: what is the primary reason for having
>> EV_HPD_INIT_SETUP and calling dp_display_config_hpd() via the event
>> thread? Does DP driver really depend on DPU irqs being installed? As
>> far as I understand, DP device uses MDSS interrupts and those IRQs are
>> available and working at the time of dp_display_probe() /
>> dp_display_bind().
> 
> HDP gpio pin has to run through DP aux module 100ms denouncing logic and 
> have its mask bits.
> 
> Therefore DP irq has to be enabled to receive DP isr with mask bits set.

So... DP irq is enabled by the MDSS, not by the DPU. Again, why does DP 
driver depend on DPU irqs being installed?

> Similar mechanism is used for mdp, dsi, etc.

And none of them uses irq_postinstall callback.

> 
> 
>>> Changes in v2:
>>> -- at commit text, dp_display_host_init() instead of host_init()
>>> -- at commit text, dp_display_host_deinit() instead of host_deinit()
>>>
>>> Changes in v3:
>>> -- re arrange to avoid commit text line over 75 chars
>>>
>>> Fixes: 989ebe7bc446 ("drm/msm/dp: do not initialize phy until plugin 
>>> interrupt received")
>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>>> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
>>> ---
>>>   drivers/gpu/drm/msm/dp/dp_display.c | 20 ++++++++++++--------
>>>   1 file changed, 12 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
>>> b/drivers/gpu/drm/msm/dp/dp_display.c
>>> index bde1a7c..1850738 100644
>>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>>> @@ -460,10 +460,12 @@ static void dp_display_host_init(struct 
>>> dp_display_private *dp)
>>>                  dp->dp_display.connector_type, dp->core_initialized,
>>>                  dp->phy_initialized);
>>>
>>> -       dp_power_init(dp->power, false);
>>> -       dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
>>> -       dp_aux_init(dp->aux);
>>> -       dp->core_initialized = true;
>>> +       if (!dp->core_initialized) {
>>> +               dp_power_init(dp->power, false);
>>> +               dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
>>> +               dp_aux_init(dp->aux);
>>> +               dp->core_initialized = true;
>>> +       }
>>>   }
>>>
>>>   static void dp_display_host_deinit(struct dp_display_private *dp)
>>> @@ -472,10 +474,12 @@ static void dp_display_host_deinit(struct 
>>> dp_display_private *dp)
>>>                  dp->dp_display.connector_type, dp->core_initialized,
>>>                  dp->phy_initialized);
>>>
>>> -       dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
>>> -       dp_aux_deinit(dp->aux);
>>> -       dp_power_deinit(dp->power);
>>> -       dp->core_initialized = false;
>>> +       if (dp->core_initialized) {
>>> +               dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
>>> +               dp_aux_deinit(dp->aux);
>>> +               dp_power_deinit(dp->power);
>>> +               dp->core_initialized = false;
>>> +       }
>>>   }
>>>
>>>   static int dp_display_usbpd_configure_cb(struct device *dev)
>>> -- 
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>>> Forum,
>>> a Linux Foundation Collaborative Project
>>>
>>

-- 
With best wishes
Dmitry