linux-kernel - Re: [PATCH 2/4] usb: typec: mux: intel_pmc_mux: Support for static SBU/HSL orientation

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Message-ID: <20200511175719.GA136540@google.com>
Date:   Mon, 11 May 2020 10:57:19 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Benson Leung <bleung@...omium.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 2/4] usb: typec: mux: intel_pmc_mux: Support for static
 SBU/HSL orientation

Hi Heikki,

Thanks a lot for looking into this. Kindly see my response inline:

On Mon, May 11, 2020 at 04:32:02PM +0300, Heikki Krogerus wrote:
> On Fri, May 08, 2020 at 02:18:44PM +0300, Heikki Krogerus wrote:
> > Hi Prashant,
> > 
> > On Thu, May 07, 2020 at 03:40:41PM -0700, Prashant Malani wrote:
> > > > +static int sbu_orientation(struct pmc_usb_port *port)
> > > > +{
> > > > +	if (port->sbu_orientation)
> > > > +		return port->sbu_orientation - 1;
> > > > +
> > > > +	return port->orientation - 1;
> > > > +}
> > > > +
> > > > +static int hsl_orientation(struct pmc_usb_port *port)
> > > > +{
> > > > +	if (port->hsl_orientation)
> > > > +		return port->hsl_orientation - 1;
> > > > +
> > > > +	return port->orientation - 1;
> > > > +}
> > > > +
> > > >  static int pmc_usb_command(struct pmc_usb_port *port, u8 *msg, u32 len)
> > > >  {
> > > >  	u8 response[4];
> > > > @@ -151,8 +170,9 @@ pmc_usb_mux_dp(struct pmc_usb_port *port, struct typec_mux_state *state)
> > > >  
> > > >  	req.mode_data = (port->orientation - 1) << PMC_USB_ALTMODE_ORI_SHIFT;
> > > >  	req.mode_data |= (port->role - 1) << PMC_USB_ALTMODE_UFP_SHIFT;
> > > > -	req.mode_data |= (port->orientation - 1) << PMC_USB_ALTMODE_ORI_AUX_SHIFT;
> > > > -	req.mode_data |= (port->orientation - 1) << PMC_USB_ALTMODE_ORI_HSL_SHIFT;
> > > > +
> > > > +	req.mode_data |= sbu_orientation(port) << PMC_USB_ALTMODE_ORI_AUX_SHIFT;
> > > 
> > > I'm curious to know what would happen when sbu-orientation == "normal".
> > > That means |port->sbu_orientation| == 1.
> > > 
> > > It sounds like what should happen is the AUX_SHIFT orientation
> > > setting should follow what |port->orientation| is, but here it
> > > looks like it will always be set to |port->sbu_orientation - 1|, i.e 0,
> > > even if port->orientation == TYPEC_ORIENTATION_REVERSE, i.e 2, meaning
> > > it should be set to 1 ?
> > 
> > I'll double check this, and get back to you..
> 
> This is not exactly an answer to your question, but it seems that
> those bits are only valid if "Alternate-Direct" message is used.
> Currently the driver does not support that message.
Could you kindly provide some detail on when "Alternate-Direct" would be
preferred to the current method?
Also, is there anything on the PMC side which is preventing the use of
"Alternate-Direct" messages? It seems like the state transition diagram
there would be simpler, although I'm likely missing significant details
here.

> 
> I think the correct thing to do now is to remove the two lines from
> the driver where those bits (ORI-HSL and ORI-Aux) are set.
I see. How would orientation then be handled in a retimer configuration
where AUX/SBU is flipped by the retimer itself?

Best regards,

-Prashant
> 
> Let me know if that's OK, and I'll update the series.
> 
> thanks,
> 
> -- 
> heikki