Re: [v3 PATCH 3/5] phy: Add USB Type-C PHY driver for rk3399

[Chris Zhong]

Hi Guenter

On 06/24/2016 10:10 AM, Guenter Roeck wrote:
> Hi Chris,
>
> On Thu, Jun 23, 2016 at 5:34 PM, Chris Zhong <zyw@xxxxxxxxxxxxxx> wrote:
> > Hi Guenter
> >
> >
> > On 06/24/2016 05:47 AM, Guenter Roeck wrote:
> > > Hi Chris,
> > >
> > > On Thu, Jun 23, 2016 at 5:51 AM, Chris Zhong <zyw@xxxxxxxxxxxxxx> wrote:
> > > > Add a PHY provider driver for the rk3399 SoC Type-c PHY. The USB
> > > > Type-C PHY is designed to support the USB3 and DP applications. The
> > > > PHY basically has two main components: USB3 and DisplyPort. USB3
> > > > operates in SuperSpeed mode and the DP can operate at RBR, HBR and
> > > > HBR2 data rates.
> > > >
> > > > Signed-off-by: Chris Zhong <zyw@xxxxxxxxxxxxxx>
> > > > Signed-off-by: Kever Yang <kever.yang@xxxxxxxxxxxxxx>
> > > [ ... ]
> > >
> > > > +
> > > > +static void tcphy_get_state(struct rockchip_typec_phy *tcphy,
> > > > +                           struct extcon_dev *edev)
> > > > +{
> > > > +       int mode;
> > > > +       bool plugged, flip, pin_assign, dfp, ufp, dp;
> > > > +
> > > > +       ufp = extcon_get_cable_state_(edev, EXTCON_USB);
> > > > +       dfp = extcon_get_cable_state_(edev, EXTCON_USB_HOST);
> > > > +       dp = extcon_get_cable_state_(edev, EXTCON_DISP_DP);
> > > > +       flip = extcon_get_cable_state_(edev, EXTCON_TYPEC_POLARITY);
> > > > +       pin_assign = extcon_get_cable_state_(edev,
> > > > EXTCON_TYPEC_PIN_ASSIGN);
> > > > +
> > > > +       plugged = ufp | dfp | dp;
> > > > +       tcphy->flip = flip;
> > > > +
> > > > +       if (plugged) {
> > > > +               if (ufp) {
> > > > +                       mode = MODE_UFP_USB;
> > > > +               } else if (dfp && !dp) {
> > > > +                       mode = MODE_DFP_USB;
> > > > +               } else if (dfp && dp) {
> > > > +                       mode = MODE_DFP_USB | MODE_DFP_DP;
> > > > +                       tcphy->pin_assign = pin_assign ? PIN_MAP_D :
> > > > PIN_MAP_B;
> > > > +               } else {
> > > > +                       mode = MODE_DFP_DP;
> > > > +                       tcphy->pin_assign = pin_assign ? PIN_MAP_C :
> > > > PIN_MAP_A;
> > > I am having trouble extracting pin_assign from our code. What
> > > determines if map A or C should be selected ?
> > >
> > > Thanks,
> > > Guenter
> > Oh, forgot rename the macro:
> >
> > PIN_MAP_ should be PIN_ASSIGN_
> >
> >
> >   IF EXTCON_TYPEC_PIN_ASSIGN is attached, Type-C get
> >   Pin_Assignment_C(for DP only mode) or Pin_Assignment_D(for DP alt mode),
> >    if detached, it get the default Assignment: A(for DP only mode) or B(for
> > DP alt mode),.
> So we are really talking about DP only vs. DP Alt mode ? If so, do we
> even need PIN_ASSIGN ? Why not just use EXTCON_DISP_DP_ALT directly ?
>
> Also, I'll have to get a better understanding what "DP only mode" and
> "DP Alt mode" actually means. DisplayPort is already a Type-C
> alternate mode, so the terminology is a bit confusing. Do you happen
> to have a description somewhere, by any chance ?
>
> Thanks,
> Guenter
The Pin Assignments is come from:
VESA DisplayPort Alt Mode on USB Type-C Standard

There are 2 mode for DP: DP only mode, and DP+USB3 mode(EXTCON_DISP_DP_ALT )
At DP only mode, DP has 4 lanes of Type-C;
At DP+USB3 mode, DP has 2 lanes, and USB3 has the other 2 lanes.

For DP only mode, there are 3 kind of pin assignments: A, C, E.
For DP + USB3 mode, there are 3 kind of pin assignments: B, D, F.

Pin Assignments C and D use the same assignments as Pin Assignments E and F.
Thence, we just need to distinguish A and C for DP only mode.
and distinguish B and D for DP + USB3 mode.
That why the phy need a PIN_ASSIGN cable.


The name of "DP Alt mode", it is DP+USB3 mode, actually.
I think if the name makes anyone confused, it can be changed to DP_USB3 mode:
The cable list could be:
EXTCON_DISP_DP
EXTCON_DISP_DP_USB3


> > I am going to add a comment for describe which PIN_ASSIGN_ should be
> > selected
> > in next version, if no one disagrees the usage of cable
> >
> >
> > >