linux-kernel - Re: [PATCH v4 2/4] usb: typec: Add support for Parade PS8830 Type-C Retimer

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Message-ID: <Zyikj47bYufXir1G@linaro.org>
Date: Mon, 4 Nov 2024 12:40:15 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rajendra Nayak <quic_rjendra@...cinc.com>,
	Sibi Sankar <quic_sibis@...cinc.com>,
	Johan Hovold <johan@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Trilok Soni <quic_tsoni@...cinc.com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/4] usb: typec: Add support for Parade PS8830 Type-C
 Retimer

On 24-11-04 11:25:40, Konrad Dybcio wrote:
> On 4.11.2024 11:16 AM, Abel Vesa wrote:
> > On 24-11-02 10:17:56, Konrad Dybcio wrote:
> >> On 1.11.2024 5:29 PM, Abel Vesa wrote:
> >>> The Parade PS8830 is a USB4, DisplayPort and Thunderbolt 4 retimer,
> >>> controlled over I2C. It usually sits between a USB/DisplayPort PHY
> >>> and the Type-C connector, and provides orientation and altmode handling.
> >>>
> >>> The boards that use this retimer are the ones featuring the Qualcomm
> >>> Snapdragon X Elite SoCs.
> >>>
> >>> Add a driver with support for the following modes:
> >>>  - DisplayPort 4-lanes
> >>>  - DisplayPort 2-lanes + USB3
> >>>  - USB3
> >>>
> >>> There is another variant of this retimer which is called PS8833. It seems
> >>> to be really similar to the PS8830, so future-proof this driver by
> >>> naming it ps883x.
> >>>
> >>> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> >>> ---
> >>
> >> [...]
> >>
> >>> +static void ps883x_configure(struct ps883x_retimer *retimer, int cfg0, int cfg1, int cfg2)
> >>> +{
> >>> +	regmap_write(retimer->regmap, 0x0, cfg0);
> >>> +	regmap_write(retimer->regmap, 0x1, cfg1);
> >>> +	regmap_write(retimer->regmap, 0x2, cfg2);
> >>> +}
> >>
> >> Somewhere between introducing regcache and dropping it, you removed
> >> muxing to a safe mode during _configure()
> > 
> > Oh, yeah, I forgot to mention that in the change log, it seems.
> > 
> > Configuring to safe mode is not needed since we always do that on 
> > unplug anyway.
> > 
> >>
> >> [...]
> >>
> >>> +	/* skip resetting if already configured */
> >>> +	if (regmap_test_bits(retimer->regmap, 0x00, BIT(0)))
> >>> +		return 0;
> >>
> >> What is that register and what does BIT(0) mean?
> > 
> > Looking at the documentation, the first register is
> > REG_USB_PORT_CONN_STATUS and spans over the first 4 bytes.
> > 
> > But it doesn't really help here.
> > 
> > BIT(0) doesn't really have a name, it just says "Connection present".
> 
> Please define both then. STATUS_CONNECTION_PRESENT sounds good for the bit.

Sure, will do.

For the register name I'll just define as:

REG_USB_PORT_CONN_STATUS_1
REG_USB_PORT_CONN_STATUS_2
REG_USB_PORT_CONN_STATUS_3

And that's it.

> 
> Konrad