linux-kernel - Re: [PATCH v2 08/10] drm/bridge: anx7625: enable HPD interrupts

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Message-ID: <3abefb09-c1b6-4339-8cd9-cd86652c35d6@quicinc.com>
Date: Fri, 21 Mar 2025 02:36:21 +0530
From: Ayushi Makhija <quic_amakhija@...cinc.com>
To: Dmitry Baryshkov <lumag@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
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Subject: Re: [PATCH v2 08/10] drm/bridge: anx7625: enable HPD interrupts

On 3/11/2025 9:09 PM, Dmitry Baryshkov wrote:
> On Tue, Mar 11, 2025 at 05:54:43PM +0530, Ayushi Makhija wrote:
>> When device enters the suspend state, it prevents
>> HPD interrupts from occurring. To address this,
>> add an additional PM runtime vote in hpd_enable().
>> This vote is removed in hpd_disable().
> 
> Is it really enough to toggle the HPD interrupts? Is there any kind of
> programming that should be moved to .hpd_enable() too (so that by
> default the bridge doesn't generate HPD interrupts)?
> 

Hi Dmirty,

I couldn't find the ANX7625 bridge driver datasheet, where all the registers information are present.

As per my understanding, we have anx7625_hpd_timer_config(), where debounce timer registers are getting set, which help to manage the detection and stability of the HPD signal.

anx7625_hpd_timer_config() is getting called from anx7625_runtime_pm_resume().

anx7625_runtime_pm_resume
   anx7625_power_on_init
       anx7625_ocm_loading_check
           anx7625_disable_pd_protocol
              anx7625_hpd_timer_config

So, I think HPD programming is already taken care in anx7625_hpd_timer_config(). anx7625_runtime_pm_resume() is getting called for both eDP and DP configuration. 

If you suggest then, I can move the anx7625_hpd_timer_config() from anx7625_disable_pd_protocol() to anx7625_bridge_hpd_enable().

Thanks,
Ayushi