Re: [PATCH] drm/msm/mdp5: enable clocks in hw_init and set_irqmask

[Archit Taneja <architt@codeaurora.org>]

On 08/28/2015 11:48 PM, Rob Clark wrote:
> On Fri, Aug 28, 2015 at 3:56 AM, Archit Taneja <architt@codeaurora.org> wrote:
>>
>>
>> On 08/27/2015 10:36 AM, Archit Taneja wrote:
>>>
>>>
>>>
>>> On 08/26/2015 08:42 PM, hali@codeaurora.org wrote:
>>>>>
>>>>> 2015-08-26 9:55 GMT-04:00  <hali@codeaurora.org>:
>>>>>>
>>>>>> Hi Archit,
>>>>>>
>>>>>>> mdp5_hw_init and mdp5_set_irqmask configure registers but may not have
>>>>>>> clocks enabled.
>>>>>>>
>>>>>>> Add mdp5_enable/disable calls in these funcs to ensure clocks are
>>>>>>> enabled. We need this until we get proper runtime pm support.
>>>>>>>
>>>>>>> Signed-off-by: Archit Taneja <architt@codeaurora.org>
>>>>>>> ---
>>>>>>>    drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c | 10 ++++++++--
>>>>>>>    drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c |  2 ++
>>>>>>>    2 files changed, 10 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c
>>>>>>> b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c
>>>>>>> index b1f73be..9fabfca 100644
>>>>>>> --- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c
>>>>>>> +++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c
>>>>>>> @@ -24,9 +24,15 @@
>>>>>>>    void mdp5_set_irqmask(struct mdp_kms *mdp_kms, uint32_t irqmask,
>>>>>>>                 uint32_t old_irqmask)
>>>>>>>    {
>>>>>>> -     mdp5_write(to_mdp5_kms(mdp_kms), REG_MDP5_MDP_INTR_CLEAR(0),
>>>>>>> +     struct mdp5_kms *mdp5_kms = to_mdp5_kms(mdp_kms);
>>>>>>> +
>>>>>>> +     mdp5_enable(mdp5_kms);
>>>>>>> +
>>>>>>> +     mdp5_write(mdp5_kms, REG_MDP5_MDP_INTR_CLEAR(0),
>>>>>>>                 irqmask ^ (irqmask & old_irqmask));
>>>>>>> -     mdp5_write(to_mdp5_kms(mdp_kms), REG_MDP5_MDP_INTR_EN(0),
>>>>>>> irqmask);
>>>>>>> +     mdp5_write(mdp5_kms, REG_MDP5_MDP_INTR_EN(0), irqmask);
>>>>>>> +
>>>>>>> +     mdp5_disable(mdp5_kms);
>>>>>>>    }
>>>>>>
>>>>>>
>>>>>> mdp5_set_irqmask() can be invoked in atomic context, clk_prepare() is
>>>>>> not
>>>>>> allowed in this function because it may cause process to sleep. We can
>>>>>> enable the clocks in the caller at initialization.
>>>
>>>
>>> Oh, oops. I missed that.
>>>
>>>>>
>>>>> iirc, it will be called with at least one spinlock held..
>>>>>
>>>>> We do already move the enable/disable_vblank() paths off to a worker
>>>>> so that we can ensure things are enabled before we get into
>>>>> update_irq()..  the only other path to update_irq() should be when
>>>>> driver code does mdp_irq_register/unregister().. so maybe we should
>>>>> just require that the mdp4/mdp5 kms code only calls those when clk's
>>>>> are already enabled (which should be mostly true already, I think)
>>>>>
>>>>> BR,
>>>>> -R
>>>>
>>>>
>>>> Yes, the only case that not been covered is mdp5_irq_postinstall(). We
>>>> can
>>>> enable clocks in this function. Actually, this is what we are doing in
>>>> downstream test.
>>>
>>>
>>> It works fine if I put it in postinstall. I'll update the patch and
>>> resend.
>>
>>
>> So, I hit an issue in both the approaches.
>>
>> When I try modeset, I get a watchdog reset once the app closes down.

I meant modetest here*

>>
>> Looking at debug logs, it looks like the issue happens when the ioctl
>> RMFB and drm_release race with each other.
>
> hmm, this seems a bit strange.. since to do the RMFB ioctl the device
> must still be open.. do we end up w/ the RMFB being an async commit
> somehow?  (Although in case of flip w/ gpu rendering still pending,
> somewhere we probably want to block on previous async commit?)

It isn't a race condition as I thought before. The RMFB ioctl isn't
asynchronous either.

The problem has to do with how msm_atomic_commit behaves when the
state we want to commit involves disabling the crtc:

In this case, we grab clocks once (in mdp5_prepare_commit), but
disable them twice (first, via mdp5_crtc_disable() in disable_outputs(),
and then in mdp5_complete_commit())

Whatever comes next will crash if it requires clocks. In this case,
drm_release's call to mdp5_crtc_cancel_pending_flip() is the first
thing that needs clocks, and it crashes there.

>
>> Within the the msm driver, this maps to mdp5_complete_commit
>> (drm_mode_rmfb path) being called before mdp5_crtc_cancel_pending_flip
>> (drm_release path). mdp5_complete_commit disables clocks, and the other
>> patch calls complete_flip, which requires clocks.
>>
>> If I wrap around complete_flip with mdp5_enable/disable calls, things
>> work fine. Although, that's not an ideal fix.
>
> I guess it is a reasonable thing to do.. but on that topic, it would
> be nice if someone had some time to look and the pending atomic
> suspend/resume/runtime-pm stuff.  I haven't really had time to follow
> that, but I guess it is a good time to revisit the mdpN_enable/disable
> stuff?

Yeah, that'd be more ideal. We're looking at runtime pm adaptation now.

Thanks,
Archit


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