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

[Abel Vesa <abel.vesa@linaro.org>]

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@linaro.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".

> 
> Konrad