[PATCH v3] drm/msm/dp: check core_initialized flag at both host_init() and host_deinit()

[Kuogee Hsieh]

On 3/2/2023 11:04 AM, Dmitry Baryshkov wrote:
> On Thu, 2 Mar 2023 at 20:41, Kuogee Hsieh <quic_khsieh at quicinc.com> wrote:
>>
>> On 3/1/2023 1:15 PM, Dmitry Baryshkov wrote:
>>> 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 at quicinc.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?
>> sorry, previously i mis understand your question -- why does DP driver
>> depend on DPU irqs being installed?
>>
>> now, I think you are asking why  dpu_irq_postinstall() ==>
>> msm_dp_irq_postinstall() ==> event_thread ==> dp_display_config_hdp()
>> ==> enable_irq(dp->irq)
>>
>> With the below test i had run, i think the reason is to make sure
>> dp->irq be requested before enable it.
>>
>> I just run the execution timing order test and collect execution order
>> as descending order at below,
>>
>> 1) dp_display_probe() -- start
>>
>> 2) dp_display_bind()
>>
>> 3) msm_dp_modeset_init()  ==> dp_display_request_irq() ==>
>> dp_display_get_next_bridge()
>>
>> 4) dpu_irq_postinstall() ==> msm_dp_irq_postinstall() ==>
>> enable_irq(dp->irq)
>>
>> 5) dp_display_probe() -- end
>>
>> dp->irq is request at msm_dp_modeset_init() and enabled after.
> Should be moved to probe.
>
>> That bring up the issue to move DP's dp_display_host_init() executed at
>> dp_display_bind().
>>
>> Since eDP have dp_dispaly_host_init() executed at
>> dp_display_get_next_bridge() which executed after dp_display_bind().
>>
>> If moved DP's dp_display_host_init() to dp_dispaly_bind() which means DP
>> will be ready to receive HPD irq before eDP ready.
> And the AUX bus population should also be moved to probe(), which
> means we should call dp_display_host_init() from probe() too.
> Having aux_bus_populate in probe would allow moving component_add() to
> the done_probing() callback, making probe/defer case more robust
>
>> This may create some uncertainties at execution flow and complicate
>> things up.
> Hopefully the changes suggested above will make it simpler.

ok, I will create another patch to

1) move dp_display_host_init() to probe()

2) move component_add() to done_probing() for eDP

3) keep DP as simple platform device (component_add() still executed in 
probe())

Meanwhile, can you approve this patch so that it will not block our 
internal daily testing?



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