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 <20220830175523.GA239841@roeck-us.net>
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From:   Badhri Jagan Sridharan <badhri@google.com>
Date:   Tue, 30 Aug 2022 17:22:04 -0700
Message-ID: <CAPTae5+xgdHUCwdrqp=Of5THUmdWLnLZu2qf1ZhysESLyPFioQ@mail.gmail.com>
Subject: Re: [PATCH v1 4/4] usb: typec: maxim_contaminant: Implement
 check_contaminant callback
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        USB <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kyle Tso <kyletso@google.com>
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On Tue, Aug 30, 2022 at 10:55 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, Aug 26, 2022 at 01:40:01AM -0700, Badhri Jagan Sridharan wrote:
> > Maxim TCPC has additional ADCs and low current(1ua) current source
> > to measure the impedance of CC and SBU pins. When tcpm invokes
> > the check_contaminant callback, Maxim TCPC measures the impedance
> > of the CC & SBU pins and when the impedance measured is less than
> > 1MOhm, it is assumed that USB-C port is contaminated. CC comparators
> > are also checked to differentiate between presence of sink and
> > contaminant. Once USB-C is deemed to be contaminated, MAXIM TCPC
> > has additional hardware to disable normal DRP toggling cycle and
> > enable 1ua on CC pins once every 2.4secs/4.8secs. Maxim TCPC
> > interrupts AP once the impedance on the CC pin is above the
> > 1MOhm threshold. The Maxim tcpc driver then signals TCPM_PORT_CLEAN
> > to restart toggling.
> >
> > Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> > ---
> >  drivers/usb/typec/tcpm/Makefile            |   2 +-
> >  drivers/usb/typec/tcpm/maxim_contaminant.c | 338 +++++++++++++++++++++
> >  drivers/usb/typec/tcpm/tcpci_maxim.c       |  34 ++-
> >  drivers/usb/typec/tcpm/tcpci_maxim.h       |  68 +++++
> >  4 files changed, 429 insertions(+), 13 deletions(-)
> >  create mode 100644 drivers/usb/typec/tcpm/maxim_contaminant.c
> >  create mode 100644 drivers/usb/typec/tcpm/tcpci_maxim.h
> >
> > diff --git a/drivers/usb/typec/tcpm/Makefile b/drivers/usb/typec/tcpm/Makefile
> > index 906d9dced8e7..81e4e9421fa0 100644
> > --- a/drivers/usb/typec/tcpm/Makefile
> > +++ b/drivers/usb/typec/tcpm/Makefile
> > @@ -7,4 +7,4 @@ obj-$(CONFIG_TYPEC_TCPCI)             += tcpci.o
> >  obj-$(CONFIG_TYPEC_RT1711H)          += tcpci_rt1711h.o
> >  obj-$(CONFIG_TYPEC_MT6360)           += tcpci_mt6360.o
> >  obj-$(CONFIG_TYPEC_TCPCI_MT6370)     += tcpci_mt6370.o
> > -obj-$(CONFIG_TYPEC_TCPCI_MAXIM)              += tcpci_maxim.o
> > +obj-$(CONFIG_TYPEC_TCPCI_MAXIM)              += tcpci_maxim.o maxim_contaminant.o
>
> This creates two separate modules, which doesn't really add any value.
> I would suggest to adjust the file names and create a single module
> named tcpci_maxim instead. Renaming tcpci_maxim.c to, say,
> tcpci_maxim_core.c and
>
> obj-$(CONFIG_TYPEC_TCPCI_MAXIM) += tcpci_maxim.o
> tcpci_maxim-y := tcpci_maxim_core.o maxim_contaminant.o
>
> should do. This would also avoid the need for exporting symbols
> from tcpci_maxim.c.

Thanks Guenter ! Done. Just sent out "[PATCH v2 3/3] usb: typec:
maxim_contaminant: Implement
check_contaminant callback".

>
> Thanks,
> Guenter