Message-ID: <04836865-6ff0-1316-6a86-c675a675ed25@linaro.org>
Date:   Fri, 20 Jan 2023 11:33:24 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>,
        Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH v2 3/4] soc: qcom: pmic_glink: Introduce altmode support

On 20/01/2023 11:06, Neil Armstrong wrote:
> On 13/01/2023 05:11, Bjorn Andersson wrote:
>> From: Bjorn Andersson <bjorn.andersson@...aro.org>
>>
>> With the PMIC GLINK service, the host OS subscribes to USB-C altmode
>> messages, which are sent by the firmware to notify the host OS about
>> state updates and HPD interrupts.
>>
>> The pmic_glink_altmode driver registers for these notifications and
>> propagates the notifications as typec_mux, typec_switch and DRM OOB
>> notifications as necessary to implement DisplayPort altmode support.
>>
>> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
>> ---
>>
>> Changes since v1:
>> - None
>>
>> Johan reported a NULL pointer dereference in
>> drm_kms_helper_hotplug_event() for HPD event being reported while the
>> MSM DRM driver is still being initalized, a separate fix has been sent
>> in hope to remidy this race condition in the MSM driver.
>>
>>   drivers/soc/qcom/Makefile             |   1 +
>>   drivers/soc/qcom/pmic_glink_altmode.c | 477 ++++++++++++++++++++++++++
>>   2 files changed, 478 insertions(+)
>>   create mode 100644 drivers/soc/qcom/pmic_glink_altmode.c
>>
>> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
>> index 29cccac472f3..f30552bf4da7 100644
>> --- a/drivers/soc/qcom/Makefile
>> +++ b/drivers/soc/qcom/Makefile
>> @@ -10,6 +10,7 @@ obj-$(CONFIG_QCOM_MDT_LOADER)    += mdt_loader.o
>>   obj-$(CONFIG_QCOM_OCMEM)    += ocmem.o
>>   obj-$(CONFIG_QCOM_PDR_HELPERS)    += pdr_interface.o
>>   obj-$(CONFIG_QCOM_PMIC_GLINK)    += pmic_glink.o
>> +obj-$(CONFIG_QCOM_PMIC_GLINK)    += pmic_glink_altmode.o
>>   obj-$(CONFIG_QCOM_QMI_HELPERS)    += qmi_helpers.o
>>   qmi_helpers-y    += qmi_encdec.o qmi_interface.o
>>   obj-$(CONFIG_QCOM_RAMP_CTRL)    += ramp_controller.o
>> diff --git a/drivers/soc/qcom/pmic_glink_altmode.c b/drivers/soc/qcom/pmic_glink_altmode.c
>> new file mode 100644
>> index 000000000000..8d2d563cb756
>> --- /dev/null
>> +++ b/drivers/soc/qcom/pmic_glink_altmode.c
>> @@ -0,0 +1,477 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2019-2020, The Linux Foundation. All rights reserved.
>> + * Copyright (c) 2022, Linaro Ltd
>> + */
>> +#include <linux/auxiliary_bus.h>
>> +#include <linux/module.h>
>> +#include <linux/of_device.h>
>> +#include <linux/mutex.h>
>> +#include <linux/property.h>
>> +#include <linux/soc/qcom/pdr.h>
>> +#include <drm/drm_bridge.h>
>> +
>> +#include <linux/usb/typec_altmode.h>
>> +#include <linux/usb/typec_dp.h>
>> +#include <linux/usb/typec_mux.h>
>> +
>> +#include <linux/soc/qcom/pmic_glink.h>
>> +
>> +#define PMIC_GLINK_MAX_PORTS    2
>> +
>> +#define USBC_SC8180X_NOTIFY_IND    0x13
>> +#define USBC_CMD_WRITE_REQ      0x15
>> +#define USBC_NOTIFY_IND        0x16
>> +
>> +#define ALTMODE_PAN_EN        0x10
>> +#define ALTMODE_PAN_ACK        0x11
>> +
>> +struct usbc_write_req {
>> +    struct pmic_glink_hdr   hdr;
>> +    __le32 cmd;
>> +    __le32 arg;
>> +    __le32 reserved;
>> +};
>> +
>> +#define NOTIFY_PAYLOAD_SIZE 16
>> +struct usbc_notify {
>> +    struct pmic_glink_hdr hdr;
>> +    char payload[NOTIFY_PAYLOAD_SIZE];
>> +    u32 reserved;
>> +};
>> +
>> +struct usbc_sc8180x_notify {
>> +    struct pmic_glink_hdr hdr;
>> +    __le32 notification;
>> +    __le32 reserved[2];
>> +};
>> +
>> +enum pmic_glink_altmode_pin_assignment {
>> +    DPAM_HPD_OUT,
>> +    DPAM_HPD_A,
>> +    DPAM_HPD_B,
>> +    DPAM_HPD_C,
>> +    DPAM_HPD_D,
>> +    DPAM_HPD_E,
>> +    DPAM_HPD_F,
>> +};
>> +
>> +struct pmic_glink_altmode;
>> +
>> +#define work_to_altmode_port(w) container_of((w), struct pmic_glink_altmode_port, work)
>> +
>> +struct pmic_glink_altmode_port {
>> +    struct pmic_glink_altmode *altmode;
>> +    unsigned int index;
>> +
>> +    struct typec_switch *typec_switch;
>> +    struct typec_mux *typec_mux;
>> +    struct typec_mux_state state;
>> +    struct typec_altmode dp_alt;
>> +
>> +    struct work_struct work;
>> +
>> +    struct drm_bridge bridge;
>> +
>> +    enum typec_orientation orientation;
>> +    u16 svid;
>> +    u8 dp_data;
>> +    u8 mode;
>> +    u8 hpd_state;
>> +    u8 hpd_irq;
>> +};
>> +
>> +#define work_to_altmode(w) container_of((w), struct pmic_glink_altmode, enable_work)
>> +
>> +struct pmic_glink_altmode {
>> +    struct device *dev;
>> +
>> +    unsigned int owner_id;
>> +
>> +    /* To synchronize WRITE_REQ acks */
>> +    struct mutex lock;
>> +
>> +    struct completion pan_ack;
>> +    struct pmic_glink_client *client;
>> +
>> +    struct work_struct enable_work;
>> +
>> +    struct pmic_glink_altmode_port ports[PMIC_GLINK_MAX_PORTS];
>> +};
>> +
>> +static int pmic_glink_altmode_request(struct pmic_glink_altmode *altmode, u32 cmd, u32 arg)
>> +{
>> +    struct usbc_write_req req = {};
>> +    unsigned long left;
>> +    int ret;
>> +
>> +    /*
>> +     * The USBC_CMD_WRITE_REQ ack doesn't identify the request, so wait for
>> +     * one ack at a time.
>> +     */
>> +    mutex_lock(&altmode->lock);
>> +
>> +    req.hdr.owner = cpu_to_le32(altmode->owner_id);
>> +    req.hdr.type = cpu_to_le32(PMIC_GLINK_REQ_RESP);
>> +    req.hdr.opcode = cpu_to_le32(USBC_CMD_WRITE_REQ);
>> +    req.cmd = cpu_to_le32(cmd);
>> +    req.arg = cpu_to_le32(arg);
>> +
>> +    ret = pmic_glink_send(altmode->client, &req, sizeof(req));
>> +    if (ret) {
>> +        dev_err(altmode->dev, "failed to send altmode request: %#x (%d)\n", cmd, ret);
>> +        goto out_unlock;
>> +    }
>> +
>> +    left = wait_for_completion_timeout(&altmode->pan_ack, 5 * HZ);
>> +    if (!left) {
>> +        dev_err(altmode->dev, "timeout waiting for altmode request ack for: %#x\n", cmd);
>> +        ret = -ETIMEDOUT;
>> +    }
>> +
>> +out_unlock:
>> +    mutex_unlock(&altmode->lock);
>> +    return ret;
>> +}
>> +
>> +static void pmic_glink_altmode_enable_dp(struct pmic_glink_altmode *altmode,
>> +                     struct pmic_glink_altmode_port *port,
>> +                     u8 mode, bool hpd_state,
>> +                     bool hpd_irq)
>> +{
>> +    struct typec_displayport_data dp_data = {};
>> +    int ret;
>> +
>> +    dp_data.status = DP_STATUS_ENABLED;
>> +    if (hpd_state)
>> +        dp_data.status |= DP_STATUS_HPD_STATE;
>> +    if (hpd_irq)
>> +        dp_data.status |= DP_STATUS_IRQ_HPD;
>> +    dp_data.conf = DP_CONF_SET_PIN_ASSIGN(mode);
>> +
>> +    port->state.alt = &port->dp_alt;
>> +    port->state.data = &dp_data;
>> +    port->state.mode = TYPEC_MODAL_STATE(mode);
>> +
>> +    ret = typec_mux_set(port->typec_mux, &port->state);
>> +    if (ret)
>> +        dev_err(altmode->dev, "failed to switch mux to DP\n");
>> +}
>> +
>> +static void pmic_glink_altmode_enable_usb(struct pmic_glink_altmode *altmode,
>> +                      struct pmic_glink_altmode_port *port)
>> +{
>> +    int ret;
>> +
>> +    port->state.alt = NULL;
>> +    port->state.data = NULL;
>> +    port->state.mode = TYPEC_STATE_USB;
>> +
>> +    ret = typec_mux_set(port->typec_mux, &port->state);
>> +    if (ret)
>> +        dev_err(altmode->dev, "failed to switch mux to USB\n");
>> +}
>> +
>> +static void pmic_glink_altmode_worker(struct work_struct *work)
>> +{
>> +    struct pmic_glink_altmode_port *alt_port = work_to_altmode_port(work);
>> +    struct pmic_glink_altmode *altmode = alt_port->altmode;
>> +
>> +    typec_switch_set(alt_port->typec_switch, alt_port->orientation);
>> +
>> +    if (alt_port->svid == USB_TYPEC_DP_SID)
>> +        pmic_glink_altmode_enable_dp(altmode, alt_port, alt_port->mode,
>> +                         alt_port->hpd_state, alt_port->hpd_irq);
>> +    else
>> +        pmic_glink_altmode_enable_usb(altmode, alt_port);
>> +
>> +    if (alt_port->hpd_state)
>> +        drm_bridge_hpd_notify(&alt_port->bridge, connector_status_connected);
>> +    else
>> +        drm_bridge_hpd_notify(&alt_port->bridge, connector_status_disconnected);
>> +
>> +    pmic_glink_altmode_request(altmode, ALTMODE_PAN_ACK, alt_port->index);
>> +};
>> +
>> +static enum typec_orientation pmic_glink_altmode_orientation(unsigned int orientation)
>> +{
>> +    if (orientation == 0)
>> +        return TYPEC_ORIENTATION_NORMAL;
>> +    else if (orientation == 1)
>> +        return TYPEC_ORIENTATION_REVERSE;
>> +    else
>> +        return TYPEC_ORIENTATION_NONE;
>> +}
>> +
>> +#define SC8180X_PORT_MASK        0x000000ff
>> +#define SC8180X_ORIENTATION_MASK    0x0000ff00
>> +#define SC8180X_MUX_MASK        0x00ff0000
>> +#define SC8180X_MODE_MASK        0x3f000000
>> +#define SC8180X_HPD_STATE_MASK        0x40000000
>> +#define SC8180X_HPD_IRQ_MASK        0x80000000
>> +
>> +static void pmic_glink_altmode_sc8180xp_notify(struct pmic_glink_altmode *altmode,
>> +                           const void *data, size_t len)
>> +{
>> +    struct pmic_glink_altmode_port *alt_port;
>> +    const struct usbc_sc8180x_notify *msg;
>> +    u32 notification;
>> +    u8 orientation;
>> +    u8 hpd_state;
>> +    u8 hpd_irq;
>> +    u16 svid;
>> +    u8 port;
>> +    u8 mode;
>> +    u8 mux;
>> +
>> +    if (len != sizeof(*msg)) {
>> +        dev_warn(altmode->dev, "invalid length of USBC_NOTIFY indication: %zd\n", len);
>> +        return;
>> +    }
>> +
>> +    msg = data;
>> +    notification = le32_to_cpu(msg->notification);
>> +    port = FIELD_GET(SC8180X_PORT_MASK, notification);
>> +    orientation = FIELD_GET(SC8180X_ORIENTATION_MASK, notification);
>> +    mux = FIELD_GET(SC8180X_MUX_MASK, notification);
>> +    mode = FIELD_GET(SC8180X_MODE_MASK, notification);
>> +    hpd_state = FIELD_GET(SC8180X_HPD_STATE_MASK, notification);
>> +    hpd_irq = FIELD_GET(SC8180X_HPD_IRQ_MASK, notification);
>> +
>> +    svid = mux == 2 ? USB_TYPEC_DP_SID : 0;
>> +
>> +    if (!altmode->ports[port].altmode) {
>> +        dev_dbg(altmode->dev, "notification on undefined port %d\n", port);
>> +        return;
>> +    }
>> +
>> +    alt_port = &altmode->ports[port];
>> +    alt_port->orientation = pmic_glink_altmode_orientation(orientation);
>> +    alt_port->svid = mux == 2 ? USB_TYPEC_DP_SID : 0;
>> +    alt_port->mode = mode;
>> +    alt_port->hpd_state = hpd_state;
>> +    alt_port->hpd_irq = hpd_irq;
>> +    schedule_work(&alt_port->work);
>> +}
>> +
>> +#define SC8280XP_DPAM_MASK    0x3f
>> +#define SC8280XP_HPD_STATE_MASK BIT(6)
>> +#define SC8280XP_HPD_IRQ_MASK    BIT(7)
>> +
>> +static void pmic_glink_altmode_sc8280xp_notify(struct pmic_glink_altmode *altmode,
>> +                           u16 svid, const void *data, size_t len)
>> +{
>> +    struct pmic_glink_altmode_port *alt_port;
>> +    const struct usbc_notify *notify;
>> +    u8 orientation;
>> +    u8 hpd_state;
>> +    u8 hpd_irq;
>> +    u8 mode;
>> +    u8 port;
>> +
>> +    if (len != sizeof(*notify)) {
>> +        dev_warn(altmode->dev, "invalid length USBC_NOTIFY_IND: %zd\n",
>> +             len);
>> +        return;
>> +    }
>> +
>> +    notify = data;
>> +
>> +    port = notify->payload[0];
>> +    orientation = notify->payload[1];
>> +    mode = FIELD_GET(SC8280XP_DPAM_MASK, notify->payload[8]) - DPAM_HPD_A;
>> +    hpd_state = FIELD_GET(SC8280XP_HPD_STATE_MASK, notify->payload[8]);
>> +    hpd_irq = FIELD_GET(SC8280XP_HPD_IRQ_MASK, notify->payload[8]);
>> +
>> +    if (!altmode->ports[port].altmode) {
>> +        dev_dbg(altmode->dev, "notification on undefined port %d\n", port);
>> +        return;
>> +    }
>> +
>> +    alt_port = &altmode->ports[port];
>> +    alt_port->orientation = pmic_glink_altmode_orientation(orientation);
>> +    alt_port->svid = svid;
>> +    alt_port->mode = mode;
>> +    alt_port->hpd_state = hpd_state;
>> +    alt_port->hpd_irq = hpd_irq;
>> +    schedule_work(&alt_port->work);
>> +}
>> +
>> +static void pmic_glink_altmode_callback(const void *data, size_t len, void *priv)
>> +{
>> +    struct pmic_glink_altmode *altmode = priv;
>> +    const struct pmic_glink_hdr *hdr = data;
>> +    u16 opcode;
>> +    u16 svid;
>> +
>> +    opcode = le32_to_cpu(hdr->opcode) & 0xff;
>> +    svid = le32_to_cpu(hdr->opcode) >> 16;
>> +
>> +    switch (opcode) {
>> +    case USBC_CMD_WRITE_REQ:
>> +        complete(&altmode->pan_ack);
>> +        break;
>> +    case USBC_NOTIFY_IND:
>> +        pmic_glink_altmode_sc8280xp_notify(altmode, svid, data, len);
>> +        break;
>> +    case USBC_SC8180X_NOTIFY_IND:
>> +        pmic_glink_altmode_sc8180xp_notify(altmode, data, len);
>> +        break;
>> +    }
>> +}
>> +
>> +static int pmic_glink_altmode_attach(struct drm_bridge *bridge,
>> +                     enum drm_bridge_attach_flags flags)
>> +{
>> +    return flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR ? 0 : -EINVAL;
>> +}
>> +
>> +static const struct drm_bridge_funcs pmic_glink_altmode_bridge_funcs = {
>> +    .attach = pmic_glink_altmode_attach,
>> +};
>> +
>> +static void pmic_glink_altmode_put_mux(void *data)
>> +{
>> +    typec_mux_put(data);
>> +}
>> +
>> +static void pmic_glink_altmode_put_switch(void *data)
>> +{
>> +    typec_switch_put(data);
>> +}
>> +
>> +static void pmic_glink_altmode_enable_worker(struct work_struct *work)
>> +{
>> +    struct pmic_glink_altmode *altmode = work_to_altmode(work);
>> +    int ret;
>> +
>> +    ret = pmic_glink_altmode_request(altmode, ALTMODE_PAN_EN, 0);
>> +    if (ret)
>> +        dev_err(altmode->dev, "failed to request altmode notifications\n");
>> +}
>> +
>> +static void pmic_glink_altmode_pdr_notify(void *priv, int state)
>> +{
>> +    struct pmic_glink_altmode *altmode = priv;
>> +
>> +    if (state == SERVREG_SERVICE_STATE_UP)
>> +        schedule_work(&altmode->enable_work);
>> +}
>> +
>> +static const struct of_device_id pmic_glink_altmode_of_quirks[] = {
>> +    { .compatible = "qcom,sc8180x-pmic-glink", .data = (void *)PMIC_GLINK_OWNER_USBC },
>> +    {}
>> +};
>> +
>> +static int pmic_glink_altmode_probe(struct auxiliary_device *adev,
>> +                    const struct auxiliary_device_id *id)
>> +{
>> +    struct pmic_glink_altmode_port *alt_port;
>> +    struct pmic_glink_altmode *altmode;
>> +    struct typec_altmode_desc mux_desc = {};
>> +    const struct of_device_id *match;
>> +    struct fwnode_handle *fwnode;
>> +    struct device *dev = &adev->dev;
>> +    u32 port;
>> +    int ret;
>> +
>> +    altmode = devm_kzalloc(dev, sizeof(*altmode), GFP_KERNEL);
>> +    if (!altmode)
>> +        return -ENOMEM;
>> +
>> +    altmode->dev = dev;
>> +
>> +    match = of_match_device(pmic_glink_altmode_of_quirks, dev->parent);
>> +    if (match)
>> +        altmode->owner_id = (unsigned long)match->data;
>> +    else
>> +        altmode->owner_id = PMIC_GLINK_OWNER_USBC_PAN;
>> +
>> +    INIT_WORK(&altmode->enable_work, pmic_glink_altmode_enable_worker);
>> +    init_completion(&altmode->pan_ack);
>> +    mutex_init(&altmode->lock);
>> +
>> +    device_for_each_child_node(dev, fwnode) {
>> +        ret = fwnode_property_read_u32(fwnode, "reg", &port);
>> +        if (ret < 0) {
>> +            dev_err(dev, "missing reg property of %pOFn\n", fwnode);
>> +            return ret;
>> +        }
>> +
>> +        if (port >= ARRAY_SIZE(altmode->ports)) {
>> +            dev_warn(dev, "invalid connector number, ignoring\n");
>> +            continue;
>> +        }
>> +
>> +        if (altmode->ports[port].altmode) {
>> +            dev_err(dev, "multiple connector definition for port %u\n", port);
>> +            return -EINVAL;
>> +        }
>> +
>> +        alt_port = &altmode->ports[port];
>> +        alt_port->altmode = altmode;
>> +        alt_port->index = port;
>> +        INIT_WORK(&alt_port->work, pmic_glink_altmode_worker);
>> +
>> +        alt_port->bridge.funcs = &pmic_glink_altmode_bridge_funcs;
>> +        alt_port->bridge.of_node = to_of_node(fwnode);
>> +        alt_port->bridge.ops = DRM_BRIDGE_OP_HPD;
>> +        alt_port->bridge.type = DRM_MODE_CONNECTOR_USB;
>> +
>> +        ret = devm_drm_bridge_add(dev, &alt_port->bridge);
>> +        if (ret)
>> +            return ret;
> 
> In my testing, the design of a bridge in the altmode driver made all the probe very fragile,
> meaning that any device that won't probe in the full usb--pmic-glink--display driver would
> prevent the whole to actually probe.
> 
> This is why drm_connector_oob_hotplug_event() was used in drivers/usb/typec/altmodes/displayport.c
> and a similar design for cec where both attach to a device so there's no probe dependency.
> 
> I think there's a possible simplification here by using :
> of_drm_find_bridge() instead on the endpoint target to get the last bridge,
> or we could probably use the same drm_connector_oob_hotplug_event() but in any way we should
> add missing pieces in drm_bridge_connector and drm/msm/dp/dp_drm.c
> 
> First in drm/msm/dp/dp_drm.c, the driver should add the of_node to the DP bridge so it can
> be found from the dp controller node.
> 
> Secondly, we could add a fwnode in drm_bridge like in drm_connector and in drm_bridge_connector_init()
> we could set the connector fwnode to the last bridge fwnode + the connector oob event handler.
> In this case the drm_connector_oob_hotplug_event() design should work.
> 
> Anyway, I think the bindings is correct, so it's a matter of implementation to avoid delaying the
> display driver probe until the pmic_glink probes entirely.

While looking closely, I don't think we can design differently except moving the bridge code
into a dummy bridge into gpu/drm/bridge, but this won't solve anything but make things even
more complex.

This design follows how generic display connector bridge is designed like in
gpu/drm/bridge/display-connector.c so it's valid.

So for the DRM Bridge part:
Acked-by: Neil Armstrong <neil.armstrong@...aro.org>

Neil

> 
> Neil
> 
>> +
>> +        alt_port->dp_alt.svid = USB_TYPEC_DP_SID;
>> +        alt_port->dp_alt.mode = USB_TYPEC_DP_MODE;
>> +        alt_port->dp_alt.active = 1;
>> +
>> +        mux_desc.svid = USB_TYPEC_DP_SID;
>> +        mux_desc.mode = USB_TYPEC_DP_MODE;
>> +        alt_port->typec_mux = fwnode_typec_mux_get(fwnode, &mux_desc);
>> +        if (IS_ERR(alt_port->typec_mux))
>> +            return dev_err_probe(dev, PTR_ERR(alt_port->typec_mux),
>> +                         "failed to acquire mode-switch for port: %d\n",
>> +                         port);
>> +
>> +        ret = devm_add_action_or_reset(dev, pmic_glink_altmode_put_mux,
>> +                           alt_port->typec_mux);
>> +        if (ret)
>> +            return ret;
>> +
>> +        alt_port->typec_switch = fwnode_typec_switch_get(fwnode);
>> +        if (IS_ERR(alt_port->typec_switch))
>> +            return dev_err_probe(dev, PTR_ERR(alt_port->typec_switch),
>> +                         "failed to acquire orientation-switch for port: %d\n",
>> +                         port);
>> +
>> +        ret = devm_add_action_or_reset(dev, pmic_glink_altmode_put_switch,
>> +                           alt_port->typec_switch);
>> +        if (ret)
>> +            return ret;
>> +    }
>> +
>> +    altmode->client = devm_pmic_glink_register_client(dev,
>> +                              altmode->owner_id,
>> +                              pmic_glink_altmode_callback,
>> +                              pmic_glink_altmode_pdr_notify,
>> +                              altmode);
>> +    return PTR_ERR_OR_ZERO(altmode->client);
>> +}
>> +
>> +static const struct auxiliary_device_id pmic_glink_altmode_id_table[] = {
>> +    { .name = "pmic_glink.altmode", },
>> +    {},
>> +};
>> +MODULE_DEVICE_TABLE(auxiliary, pmic_glink_altmode_id_table);
>> +
>> +static struct auxiliary_driver pmic_glink_altmode_driver = {
>> +    .name = "pmic_glink_altmode",
>> +    .probe = pmic_glink_altmode_probe,
>> +    .id_table = pmic_glink_altmode_id_table,
>> +};
>> +
>> +module_auxiliary_driver(pmic_glink_altmode_driver);
>> +
>> +MODULE_DESCRIPTION("Qualcomm PMIC GLINK Altmode driver");
>> +MODULE_LICENSE("GPL");
> 

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