Re: [PATCH v4 5/7] platform/chrome: cros_ec_typec: Displayport support

[Abhishek Pandit-Subedi]

On Tue, Dec 10, 2024 at 4:08 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote:
>
> Quoting Abhishek Pandit-Subedi (2024-12-06 15:38:16)
> > diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> > index e3eabe5e42ac..0f3bc335f583 100644
> > --- a/drivers/platform/chrome/cros_ec_typec.c
> > +++ b/drivers/platform/chrome/cros_ec_typec.c
> > @@ -18,6 +18,7 @@
> >
> >  #include "cros_ec_typec.h"
> >  #include "cros_typec_vdm.h"
> > +#include "cros_typec_altmode.h"
> >
> >  #define DRV_NAME "cros-ec-typec"
> >
> > @@ -290,15 +291,15 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
> >         struct typec_altmode *amode;
> >
> >         /* All PD capable CrOS devices are assumed to support DP altmode. */
> > +       memset(&desc, 0, sizeof(desc));
> >         desc.svid = USB_TYPEC_DP_SID;
> >         desc.mode = USB_TYPEC_DP_MODE;
> >         desc.vdo = DP_PORT_VDO;
> > -       amode = typec_port_register_altmode(port->port, &desc);
> > +       amode = cros_typec_register_displayport(port, &desc,
> > +                                               typec->ap_driven_altmode);
> >         if (IS_ERR(amode))
> >                 return PTR_ERR(amode);
> >         port->port_altmode[CROS_EC_ALTMODE_DP] = amode;
> > -       typec_altmode_set_drvdata(amode, port);
> > -       amode->ops = &port_amode_ops;
> >
> >         /*
> >          * Register TBT compatibility alt mode. The EC will not enter the mode
> > @@ -575,6 +576,10 @@ static int cros_typec_enable_dp(struct cros_typec_data *typec,
> >         if (!ret)
> >                 ret = typec_mux_set(port->mux, &port->state);
> >
> > +       if (!ret)
> > +               cros_typec_displayport_status_update(port->state.alt,
>
> Should we forward the return value from here?
Done

>
> > +                                                    port->state.data);
> > +
> >         return ret;
> >  }
> >
> > @@ -1254,6 +1259,8 @@ static int cros_typec_probe(struct platform_device *pdev)
> >
> >         typec->typec_cmd_supported = cros_ec_check_features(ec_dev, EC_FEATURE_TYPEC_CMD);
> >         typec->needs_mux_ack = cros_ec_check_features(ec_dev, EC_FEATURE_TYPEC_MUX_REQUIRE_AP_ACK);
> > +       typec->ap_driven_altmode = cros_ec_check_features(
> > +               ec_dev, EC_FEATURE_TYPEC_REQUIRE_AP_MODE_ENTRY);
> >
> >         ret = cros_ec_cmd(typec->ec, 0, EC_CMD_USB_PD_PORTS, NULL, 0,
> >                           &resp, sizeof(resp));
> > diff --git a/drivers/platform/chrome/cros_ec_typec.h b/drivers/platform/chrome/cros_ec_typec.h
> > index deda180a646f..9fd5342bb0ad 100644
> > --- a/drivers/platform/chrome/cros_ec_typec.h
> > +++ b/drivers/platform/chrome/cros_ec_typec.h
> > @@ -39,6 +39,7 @@ struct cros_typec_data {
> >         struct work_struct port_work;
> >         bool typec_cmd_supported;
> >         bool needs_mux_ack;
> > +       bool ap_driven_altmode;
>
> Do we need to stash this? Can we cros_ec_check_features() in
> cros_typec_init_ports() and pass the bool to
> cros_typec_register_port_altmodes() instead to save a struct member?

We don't need to stash this but it keeps the feature checks
consistently in `cros_typec_probe`.

>
> >  };
> >
> >  /* Per port data. */
> > diff --git a/drivers/platform/chrome/cros_typec_altmode.c b/drivers/platform/chrome/cros_typec_altmode.c
> > new file mode 100644
> > index 000000000000..bb7c7ad2ff6e
> > --- /dev/null
> > +++ b/drivers/platform/chrome/cros_typec_altmode.c
> > @@ -0,0 +1,281 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Alt-mode implementation on ChromeOS EC.
> > + *
> > + * Copyright 2024 Google LLC
> > + * Author: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>
> > + */
> > +#include "cros_ec_typec.h"
> > +
> > +#include <linux/usb/typec_dp.h>
> > +#include <linux/usb/pd_vdo.h>
>
> Please include workqueue.h, mutex.h, etc. for things used in this file.
Done. Btw, is there a script that does this for you in the kernel like
include-what-you-use does for userspace?

>
> > +
> > +#include "cros_typec_altmode.h"
> > +
> > +struct cros_typec_altmode_data {
> > +       struct work_struct work;
> > +       struct cros_typec_port *port;
> > +       struct typec_altmode *alt;
> > +       bool ap_mode_entry;
>
> The UCSI driver (drivers/usb/typec/ucsi/displayport.c) calls this
> 'override', can it be named the same thing? I also see that the UCSI
> driver has two bools, 'override' and 'initialized', which seems to be to
> support a DP_CMD_CONFIGURE that will respond with an ACK and then the
> next DP_CMD_CONFIGURE will call ucsi_altmode_update_active() to set the
> altmode as active. Maybe the same method can be followed here so that on
> older chromebooks where EC is in control of mode entry we can emulate
> entering the mode?

The reason it's called `override` in UCSI is because the feature is
called "alternate mode override supported". When this optional bit is
set, the UCSI method "SET_NEW_CAM" can be used to change what
alternate mode is active. However, it behaves differently from cros_ec
because even when override is set, the PD controller can/will still
autonomously enter a mode on connection. Whereas on cros_ec_typec, if
you set "ap-driven-mode", the EC will not enter any modes until the AP
tells it to.

Also, the reason the UCSI driver does the DP_CMD_CONFIGURE dance is
because the UCSI command, SET_NEW_CAM, requires the DP configuration
VDO as a parameter. Since UCSI doesn't define a VDM mechanism, the
UCSI driver fakes the ".entry" call and then uses the first
DP_CONFIGURE to do the actual entry. This also doesn't match the
cros_ec driver (either ap-driven or not) because the interface does
not allow setting the DP VDO at all. DP_CONFIGURE will be generated
and consumed entirely within the EC and all we can really use is the
mux update to generate a status update for the DP state machine.

Right now, EC driven Chromebooks will simply report active/inactive
for DP without reporting any configuration/status info. If you want to
handle DP_CONFIGURE and DP_STATUS from the altmode driver, you'll need
to fake the interactions in the port driver in a subsequent CL.

>
> > +
> > +       struct mutex lock;
> > +       u32 header;
> > +       u32 *vdo_data;
> > +       u8 vdo_size;
> > +
> > +       u16 sid;
> > +       u8 mode;
> > +};
> > +
> > +struct cros_typec_dp_data {
> > +       struct cros_typec_altmode_data adata;
> > +       struct typec_displayport_data data;
> > +       bool configured;
> > +       bool pending_status_update;
> > +};
> > +
> > +static void cros_typec_altmode_work(struct work_struct *work)
> > +{
> > +       struct cros_typec_altmode_data *data =
> > +               container_of(work, struct cros_typec_altmode_data, work);
> > +
> > +       mutex_lock(&data->lock);
> > +
> > +       if (typec_altmode_vdm(data->alt, data->header, data->vdo_data,
> > +                             data->vdo_size))
> > +               dev_err(&data->alt->dev, "VDM 0x%x failed", data->header);
>
> These printks need newlines.
Done.

>
>                dev_err(&data->alt->dev, "VDM 0x%x failed\n", data->header);
>
> > +
> > +       data->header = 0;
> > +       data->vdo_data = NULL;
> > +       data->vdo_size = 0;
> > +
> > +       mutex_unlock(&data->lock);
> > +}
> > +
> > +static int cros_typec_altmode_enter(struct typec_altmode *alt, u32 *vdo)
> > +{
> > +       struct cros_typec_altmode_data *data = typec_altmode_get_drvdata(alt);
> > +       struct ec_params_typec_control req = {
> > +               .port = data->port->port_num,
> > +               .command = TYPEC_CONTROL_COMMAND_ENTER_MODE,
> > +       };
> > +       int svdm_version;
> > +       int ret;
> > +
> > +       if (!data->ap_mode_entry) {
> > +               dev_warn(&alt->dev,
> > +                        "EC does not support AP driven mode entry\n");
>
> Like this one.
>
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       if (data->sid == USB_TYPEC_DP_SID)
> > +               req.mode_to_enter = CROS_EC_ALTMODE_DP;
> > +       else
> > +               return -EOPNOTSUPP;
> > +
> > +       ret = cros_ec_cmd(data->port->typec_data->ec, 0, EC_CMD_TYPEC_CONTROL,
>
> Do we plan to delete drivers/platform/chrome/cros_typec_vdm.c file at
> some point? I ask because 'port_amode_ops' becomes unused after this
> series.

Yes - I don't think we ever launched with the VDM request/response
feature enabled. I was going to do it as a follow-up to this CL to
handle attention.

>
> > +                         &req, sizeof(req), NULL, 0);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       svdm_version = typec_altmode_get_svdm_version(alt);
> > +       if (svdm_version < 0)
> > +               return svdm_version;
> > +
> > +       mutex_lock(&data->lock);
> > +
> > +       data->header = VDO(data->sid, 1, svdm_version, CMD_ENTER_MODE);
> > +       data->header |= VDO_OPOS(data->mode);
> > +       data->header |= VDO_CMDT(CMDT_RSP_ACK);
> > +       data->vdo_data = NULL;
> > +       data->vdo_size = 1;
> > +       schedule_work(&data->work);
> > +
> > +       mutex_unlock(&data->lock);
> > +       return ret;
> > +}
> > +
> > +static int cros_typec_altmode_exit(struct typec_altmode *alt)
> > +{
> > +       struct cros_typec_altmode_data *data = typec_altmode_get_drvdata(alt);
> > +       struct ec_params_typec_control req = {
> > +               .port = data->port->port_num,
> > +               .command = TYPEC_CONTROL_COMMAND_EXIT_MODES,
> > +       };
> > +       int svdm_version;
> > +       int ret;
> > +
> > +       if (!data->ap_mode_entry) {
> > +               dev_warn(&alt->dev,
> > +                        "EC does not support AP driven mode exit\n");
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       ret = cros_ec_cmd(data->port->typec_data->ec, 0, EC_CMD_TYPEC_CONTROL,
> > +                         &req, sizeof(req), NULL, 0);
> > +
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       svdm_version = typec_altmode_get_svdm_version(alt);
> > +       if (svdm_version < 0)
> > +               return svdm_version;
> > +
> > +       mutex_lock(&data->lock);
> > +
> > +       data->header = VDO(data->sid, 1, svdm_version, CMD_EXIT_MODE);
> > +       data->header |= VDO_OPOS(data->mode);
> > +       data->header |= VDO_CMDT(CMDT_RSP_ACK);
> > +       data->vdo_data = NULL;
> > +       data->vdo_size = 1;
> > +       schedule_work(&data->work);
> > +
> > +       mutex_unlock(&data->lock);
> > +       return ret;
> > +}
> > +
> > +static int cros_typec_displayport_vdm(struct typec_altmode *alt, u32 header,
> > +                                     const u32 *data, int count)
> > +{
> > +       struct cros_typec_dp_data *dp_data = typec_altmode_get_drvdata(alt);
> > +       struct cros_typec_altmode_data *adata = &dp_data->adata;
> > +
> > +
> > +       int cmd_type = PD_VDO_CMDT(header);
> > +       int cmd = PD_VDO_CMD(header);
> > +       int svdm_version;
> > +
> > +       svdm_version = typec_altmode_get_svdm_version(alt);
> > +       if (svdm_version < 0)
> > +               return svdm_version;
> > +
> > +       mutex_lock(&adata->lock);
> > +
> > +       switch (cmd_type) {
> > +       case CMDT_INIT:
> > +               if (PD_VDO_SVDM_VER(header) < svdm_version) {
> > +                       typec_partner_set_svdm_version(adata->port->partner,
> > +                                                      PD_VDO_SVDM_VER(header));
> > +                       svdm_version = PD_VDO_SVDM_VER(header);
> > +               }
> > +
> > +               adata->header = VDO(adata->sid, 1, svdm_version, cmd);
> > +               adata->header |= VDO_OPOS(adata->mode);
> > +
> > +               /*
> > +                * DP_CMD_CONFIGURE: We can't actually do anything with the
> > +                * provided VDO yet so just send back an ACK.
> > +                *
> > +                * DP_CMD_STATUS_UPDATE: We wait for Mux changes to send
> > +                * DPStatus Acks.
> > +                */
> > +               switch (cmd) {
> > +               case DP_CMD_CONFIGURE:
> > +                       dp_data->data.conf = *data;
> > +                       adata->header |= VDO_CMDT(CMDT_RSP_ACK);
> > +                       dp_data->configured = true;
> > +                       schedule_work(&adata->work);
> > +                       break;
> > +               case DP_CMD_STATUS_UPDATE:
> > +                       dp_data->pending_status_update = true;
> > +                       break;
> > +               default:
> > +                       adata->header |= VDO_CMDT(CMDT_RSP_ACK);
> > +                       schedule_work(&adata->work);
> > +                       break;
> > +               }
> > +
> > +               break;
> > +       default:
> > +               break;
> > +       }
> > +
> > +       mutex_unlock(&adata->lock);
> > +       return 0;
> > +}
> > +
> > +static int cros_typec_altmode_vdm(struct typec_altmode *alt, u32 header,
> > +                                     const u32 *data, int count)
> > +{
> > +       struct cros_typec_altmode_data *adata = typec_altmode_get_drvdata(alt);
> > +
> > +       if (!adata->ap_mode_entry)
> > +               return -EOPNOTSUPP;
> > +
> > +       if (adata->sid == USB_TYPEC_DP_SID)
> > +               return cros_typec_displayport_vdm(alt, header, data, count);
> > +
> > +       return -EINVAL;
> > +}
> > +
> > +static const struct typec_altmode_ops cros_typec_altmode_ops = {
> > +       .enter = cros_typec_altmode_enter,
> > +       .exit = cros_typec_altmode_exit,
> > +       .vdm = cros_typec_altmode_vdm,
> > +};
> > +
> > +#if IS_ENABLED(CONFIG_TYPEC_DP_ALTMODE)
> > +int cros_typec_displayport_status_update(struct typec_altmode *altmode,
> > +                                        struct typec_displayport_data *data)
> > +{
> > +       struct cros_typec_dp_data *dp_data =
> > +               typec_altmode_get_drvdata(altmode);
> > +       struct cros_typec_altmode_data *adata = &dp_data->adata;
> > +
> > +       if (!dp_data->pending_status_update) {
> > +               dev_dbg(&altmode->dev,
> > +                       "Got DPStatus without a pending request");
> > +               return 0;
> > +       }
> > +
> > +       if (dp_data->configured && dp_data->data.conf != data->conf)
> > +               dev_dbg(&altmode->dev,
> > +                       "DP Conf doesn't match. Requested 0x%04x, Actual 0x%04x",
> > +                       dp_data->data.conf, data->conf);
> > +
> > +       mutex_lock(&adata->lock);
> > +
> > +       dp_data->data = *data;
> > +       dp_data->pending_status_update = false;
> > +       adata->header |= VDO_CMDT(CMDT_RSP_ACK);
> > +       adata->vdo_data = &dp_data->data.status;
> > +       adata->vdo_size = 2;
> > +       schedule_work(&adata->work);
> > +
> > +       mutex_unlock(&adata->lock);
> > +
> > +       return 0;
> > +}
> > +
> > +struct typec_altmode *
> > +cros_typec_register_displayport(struct cros_typec_port *port,
> > +                               struct typec_altmode_desc *desc,
> > +                               bool ap_mode_entry)
> > +{
> > +       struct typec_altmode *alt;
> > +       struct cros_typec_altmode_data *data;
>
> Can you name it 'adata' consistently? That makes it easy to search for
> 'adata' in this file and know it's always talking about a struct
> cros_typec_altmode_data type of data.
Done

>
> > +
> > +       alt = typec_port_register_altmode(port->port, desc);
> > +       if (IS_ERR(alt))
> > +               return alt;
> > +
> > +       data = devm_kzalloc(&alt->dev, sizeof(*data), GFP_KERNEL);
> > +       if (!data) {
> > +               typec_unregister_altmode(alt);
> > +               return ERR_PTR(-ENOMEM);
> > +       }
> > +
> > +       INIT_WORK(&data->work, cros_typec_altmode_work);
> > +       mutex_init(&data->lock);
> > +       data->alt = alt;
> > +       data->port = port;
> > +       data->ap_mode_entry = ap_mode_entry;
> > +       data->sid = desc->svid;
> > +       data->mode = desc->mode;
> > +
> > +       typec_altmode_set_ops(alt, &cros_typec_altmode_ops);
> > +       typec_altmode_set_drvdata(alt, data);
> > +
> > +       return alt;
> > +}
> > +#endif
> > diff --git a/drivers/platform/chrome/cros_typec_altmode.h b/drivers/platform/chrome/cros_typec_altmode.h
> > new file mode 100644
> > index 000000000000..c6f8fb02c99c
> > --- /dev/null
> > +++ b/drivers/platform/chrome/cros_typec_altmode.h
> > @@ -0,0 +1,34 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +#ifndef __CROS_TYPEC_ALTMODE_H__
> > +#define __CROS_TYPEC_ALTMODE_H__
>
> #include <linux/kconfig.h> for IS_ENABLED()
> #include <linux/usb/typec.h> for typec_port_register_altmode()
Done

>
> > +
> > +struct cros_typec_port;
> > +struct typec_altmode;
> > +struct typec_altmode_desc;
> > +struct typec_displayport_data;
> > +
> > +#if IS_ENABLED(CONFIG_TYPEC_DP_ALTMODE)
> > +struct typec_altmode *
> > +cros_typec_register_displayport(struct cros_typec_port *port,
> > +                               struct typec_altmode_desc *desc,
> > +                               bool ap_mode_entry);
> > +
> > +int cros_typec_displayport_status_update(struct typec_altmode *altmode,
> > +                                        struct typec_displayport_data *data);
> > +#else
> > +static inline struct typec_altmode *
> > +cros_typec_register_displayport(struct cros_typec_port *port,
> > +                               struct typec_altmode_desc *desc,
> > +                               bool ap_mode_entry)
> > +{
> > +       return typec_port_register_altmode(port->port, desc);
> > +}