linux-kernel - Re: [PATCH 2/3] regulator: qcom_usb_vbus: Add support for PMI8998 VBUS

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Message-ID: <20250212085609.06e0f949@jamesmacinnes-VirtualBox>
Date: Wed, 12 Feb 2025 08:56:09 -0800
From: "James A. MacInnes" <james.a.macinnes@...il.com>
To: Caleb Connolly <caleb.connolly@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, andersson@...nel.org, konradybcio@...nel.org,
 quic_wcheng@...cinc.com, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, lgirdwood@...il.com, broonie@...nel.org
Subject: Re: [PATCH 2/3] regulator: qcom_usb_vbus: Add support for PMI8998
 VBUS

On Wed, 12 Feb 2025 15:29:54 +0000
Caleb Connolly <caleb.connolly@...aro.org> wrote:

Hi Caleb,

> Hi James,
> 
> On 2/12/25 01:07, James A. MacInnes wrote:
> > This patch extends the Qualcomm USB VBUS regulator driver to support
> > PMI8998 PMIC alongside the existing support for PM8150B.  
> 
> Thanks for the patch!

Happy to try and contribute. I know that the working Type-C port is
going to be a misery after the relative simplicity of pushing the VBUS
upstream.
> > 
> > Key changes:
> > - Added current limit tables specific to PMI8998.  
> 
> I also played around with vbus on PMI8998 before for type-c support 
> (unfortunately didn't make it's way to the lists yet...) and I needed 
> some additional changes for this to work correctly. I found that it
> was possible for the overcurrent protection to be hit if the type-c
> port manager allowed the peripheral to pull current too early, and
> it's necessary to allow 2.5ms enable time.
> 
> PM8150b doesn't have these limitations (and supports the instant
> power role switch feature that's part of the type-c PD spec, allowing
> the power role to be switched without either side losing power e.g.
> when you unplug the power supply from a dock), hence it's only
> necessary for PMI8998.
> 
> I would suggest implementing a proper .is_enabled op to poll the
> status register for OTG_STATE_ENABLED and configuring 
> qcom_usb_vbus_rdesc.enable_time = 250000;
> 
> Kind regards,
> 

Technical question for you in regards to the VBUS overcurrent and
timing for the PMI8998. I would like to try and reproduce what you have
seen as my system hasn't had switching issues, but then again the TCPM
system may be covering the exact bug you are mentioning. I also
searched for some definite bit in the 4.9 Android driver and was left
wanting. As of yet, I have not had issues with the overcurrent
protecction.

I will be all too happy to migrate to the PM8150B and its associated
SoCs and leave the 845 platform to history.

Thank you for your feedback and I look forward to narrowing down this
issue.

Best wishes,