Date:   Fri, 20 Jan 2023 11:06:41 +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 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.

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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