Date:   Mon, 4 Oct 2021 09:42:19 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Souradeep Chowdhury <schowdhu@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org,
        Bryan O'Donoghue <pure.logic@...us-software.ie>,
        Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
        ckadabi@...eaurora.org, tsoni@...eaurora.org,
        bryanh@...eaurora.org, psodagud@...eaurora.org,
        satyap@...eaurora.org, pheragu@...eaurora.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: Re: [PATCH V0 4/7] usb: common: eud: Added the driver support for
 Embedded USB Debugger(EUD)

On Mon 04 Oct 04:16 PDT 2021, Souradeep Chowdhury wrote:

> Add support for control peripheral of EUD (Embedded USB Debugger) to
> listen to events such as USB attach/detach, pet EUD to indicate software
> is functional.Reusing the platform device kobj, sysfs entry 'enable' is
> created to enable or disable EUD.
> 
> To enable the eud the following needs to be done
> echo 1 > /sys/bus/platform/.../enable
> 
> To disable eud, following is the command
> echo 0 > /sys/bus/platform/.../enable
> 
> Signed-off-by: Souradeep Chowdhury <schowdhu@...eaurora.org>
> ---
>  Documentation/ABI/testing/sysfs-driver-eud |   7 +
>  drivers/usb/common/Kconfig                 |   9 +
>  drivers/usb/common/Makefile                |   1 +
>  drivers/usb/common/qcom_eud.c              | 256 +++++++++++++++++++++++++++++
>  4 files changed, 273 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-driver-eud
>  create mode 100644 drivers/usb/common/qcom_eud.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-eud b/Documentation/ABI/testing/sysfs-driver-eud
> new file mode 100644
> index 0000000..14a02da
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-eud
> @@ -0,0 +1,7 @@
> +What:		/sys/bus/platform/.../enable
> +Date:           October 2021
> +Contact:        Souradeep Chowdhury <schowdhu@...eaurora.org>
> +Description:
> +		The Enable/Disable sysfs interface for Embedded
> +		USB Debugger(EUD).This enables and disables the
> +		EUD based on a 1 or a 0 value.
> diff --git a/drivers/usb/common/Kconfig b/drivers/usb/common/Kconfig
> index 5e8a04e..669b3fe 100644
> --- a/drivers/usb/common/Kconfig
> +++ b/drivers/usb/common/Kconfig
> @@ -50,3 +50,12 @@ config USB_CONN_GPIO
> 
>  	  To compile the driver as a module, choose M here: the module will
>  	  be called usb-conn-gpio.ko
> +
> +config USB_QCOM_EUD
> +	tristate "USB EUD Driver"
> +	select USB_ROLE_SWITCH
> +	help
> +	  This module enables support for Qualcomm Technologies, Inc.
> +	  Embedded USB Debugger (EUD). The EUD is a control peripheral
> +	  which reports VBUS attach/detach events and has USB-based
> +	  debug and trace capabilities.
> diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
> index 8ac4d21..eb66045 100644
> --- a/drivers/usb/common/Makefile
> +++ b/drivers/usb/common/Makefile
> @@ -11,3 +11,4 @@ usb-common-$(CONFIG_USB_LED_TRIG) += led.o
>  obj-$(CONFIG_USB_CONN_GPIO)	+= usb-conn-gpio.o
>  obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
>  obj-$(CONFIG_USB_ULPI_BUS)	+= ulpi.o
> +obj-$(CONFIG_USB_QCOM_EUD)      += qcom_eud.o
> diff --git a/drivers/usb/common/qcom_eud.c b/drivers/usb/common/qcom_eud.c
> new file mode 100644
> index 0000000..7a92fff
> --- /dev/null
> +++ b/drivers/usb/common/qcom_eud.c
> @@ -0,0 +1,256 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/usb/role.h>
> +
> +#define EUD_REG_INT1_EN_MASK	0x0024
> +#define EUD_REG_INT_STATUS_1	0x0044
> +#define EUD_REG_CTL_OUT_1	0x0074
> +#define EUD_REG_VBUS_INT_CLR	0x0080
> +#define EUD_REG_CSR_EUD_EN	0x1014
> +#define EUD_REG_SW_ATTACH_DET	0x1018
> +#define EUD_REG_EUD_EN2         0x0000
> +
> +#define EUD_ENABLE		BIT(0)
> +#define EUD_INT_PET_EUD		BIT(0)
> +#define EUD_INT_VBUS		BIT(2)
> +#define EUD_INT_SAFE_MODE	BIT(4)
> +#define EUD_INT_ALL		(EUD_INT_VBUS|EUD_INT_SAFE_MODE)
> +
> +struct eud_chip {
> +	struct device			*dev;
> +	struct usb_role_switch		*role_sw;
> +	void __iomem			*eud_reg_base;
> +	void __iomem			*eud_mode_mgr2_phys_base;
> +	unsigned int			int_status;
> +	int				enable;
> +	int				eud_irq;
> +	bool				usb_attach;
> +
> +};
> +
> +static int enable_eud(struct eud_chip *priv)
> +{
> +	writel(EUD_ENABLE, priv->eud_reg_base + EUD_REG_CSR_EUD_EN);
> +	writel(EUD_INT_VBUS | EUD_INT_SAFE_MODE,
> +			priv->eud_reg_base + EUD_REG_INT1_EN_MASK);
> +	writel(1, priv->eud_mode_mgr2_phys_base + EUD_REG_EUD_EN2);
> +
> +	return usb_role_switch_set_role(priv->role_sw, USB_ROLE_DEVICE);
> +}
> +
> +static void disable_eud(struct eud_chip *priv)
> +{
> +	writel(0, priv->eud_reg_base + EUD_REG_CSR_EUD_EN);
> +	writel(0, priv->eud_mode_mgr2_phys_base + EUD_REG_EUD_EN2);
> +}
> +
> +static ssize_t enable_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct eud_chip *chip = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%d", chip->enable);
> +}
> +
> +static ssize_t enable_store(struct device *dev,
> +		struct device_attribute *attr,
> +		const char *buf, size_t count)
> +{
> +	struct eud_chip *chip = dev_get_drvdata(dev);
> +	unsigned long enable;
> +	int ret;
> +
> +	if (kstrtoul(buf, 16, &enable))
> +		return -EINVAL;
> +
> +	if (enable == 1) {
> +		ret = enable_eud(chip);
> +		if (!ret)
> +			chip->enable = enable;
> +	} else if (enable == 0) {
> +		disable_eud(chip);
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR_RW(enable);
> +
> +static const struct device_attribute *eud_attrs[] = {
> +	&dev_attr_enable,
> +	NULL,
> +};
> +
> +static void usb_attach_detach(struct eud_chip *chip)
> +{
> +	u32 reg;
> +
> +	/* read ctl_out_1[4] to find USB attach or detach event */
> +	reg = readl(chip->eud_reg_base + EUD_REG_CTL_OUT_1);
> +	if (reg & EUD_INT_SAFE_MODE)
> +		chip->usb_attach = true;
> +	else
> +		chip->usb_attach = false;
> +
> +	/* set and clear vbus_int_clr[0] to clear interrupt */
> +	writel(BIT(0), chip->eud_reg_base + EUD_REG_VBUS_INT_CLR);
> +	writel(0, chip->eud_reg_base + EUD_REG_VBUS_INT_CLR);
> +}
> +
> +static void pet_eud(struct eud_chip *chip)
> +{
> +	u32 reg;
> +	int ret;
> +
> +	/* read sw_attach_det[0] to find attach/detach event */
> +	reg = readl(chip->eud_reg_base +  EUD_REG_SW_ATTACH_DET);
> +	if (reg & EUD_INT_PET_EUD) {
> +		/* Detach & Attach pet for EUD */
> +		writel(0, chip->eud_reg_base + EUD_REG_SW_ATTACH_DET);
> +		/* Delay to make sure detach pet is done before attach pet */
> +		ret = readl_poll_timeout(chip->eud_reg_base + EUD_REG_SW_ATTACH_DET,
> +					reg, (reg == 0), 1, 100);
> +		if (ret) {
> +			dev_err(chip->dev, "Detach pet failed\n");
> +			return;
> +		}
> +
> +		writel(EUD_INT_PET_EUD, chip->eud_reg_base +
> +				EUD_REG_SW_ATTACH_DET);
> +	} else {
> +		/* Attach pet for EUD */
> +		writel(EUD_INT_PET_EUD, chip->eud_reg_base +
> +				EUD_REG_SW_ATTACH_DET);
> +	}
> +}
> +
> +static irqreturn_t handle_eud_irq(int irq, void *data)
> +{
> +	struct eud_chip *chip = data;
> +	u32 reg;
> +
> +	/* read status register and find out which interrupt triggered */
> +	reg = readl(chip->eud_reg_base +  EUD_REG_INT_STATUS_1);
> +	switch (reg & EUD_INT_ALL) {
> +	case EUD_INT_VBUS:
> +		chip->int_status = EUD_INT_VBUS;
> +		usb_attach_detach(chip);
> +		return IRQ_WAKE_THREAD;
> +	case EUD_INT_SAFE_MODE:
> +		pet_eud(chip);
> +		break;
> +	default:
> +		return IRQ_NONE;
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t handle_eud_irq_thread(int irq, void *data)
> +{
> +	struct eud_chip *chip = data;
> +	int ret;
> +
> +	if (chip->int_status == EUD_INT_VBUS) {
> +		if (chip->usb_attach)
> +			ret = usb_role_switch_set_role(chip->role_sw, USB_ROLE_DEVICE);
> +		else
> +			ret = usb_role_switch_set_role(chip->role_sw, USB_ROLE_HOST);

How does this work if I have a Type-C controller wired up to the dwc3
and it has negotiated that we're supposed to be in device mode?

Shouldn't this driver somehow work as an override only when EUD is
enabled, but otherwise let the Type-C controller deal with things?

Or is this interrupt simply not delivered when EUD is disabled, so that
it happens to work as expected?

> +		if (ret)
> +			dev_err(chip->dev, "failed to set role switch\n");
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int eud_probe(struct platform_device *pdev)
> +{
> +	struct eud_chip *chip;
> +	int ret;
> +
> +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> +	if (!chip)
> +		return -ENOMEM;
> +
> +	chip->dev = &pdev->dev;
> +
> +	chip->role_sw = usb_role_switch_get(chip->dev);
> +	if (IS_ERR(chip->role_sw)) {
> +		if (PTR_ERR(chip->role_sw) != -EPROBE_DEFER)
> +			dev_err(chip->dev, "failed to get role switch\n");
> +
> +		return PTR_ERR(chip->role_sw);

Please use
		dev_err_probe(chip->dev, PTR_ERR(chip->role_sw), "failed to...\n");

> +	}
> +
> +	chip->eud_reg_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(chip->eud_reg_base))
> +		return PTR_ERR(chip->eud_reg_base);
> +
> +	chip->eud_mode_mgr2_phys_base = devm_platform_ioremap_resource(pdev, 1);
> +	if (IS_ERR(chip->eud_mode_mgr2_phys_base))
> +		return PTR_ERR(chip->eud_mode_mgr2_phys_base);
> +
> +	chip->eud_irq = platform_get_irq(pdev, 0);
> +	ret = devm_request_threaded_irq(&pdev->dev, chip->eud_irq, handle_eud_irq,
> +			handle_eud_irq_thread, IRQF_ONESHOT, NULL, chip);
> +	if (ret)

This deserved another dev_err_probe()

Thanks,
Bjorn

> +		return ret;
> +
> +	device_init_wakeup(&pdev->dev, true);
> +	enable_irq_wake(chip->eud_irq);
> +
> +	platform_set_drvdata(pdev, chip);
> +
> +	ret = device_create_file(&pdev->dev, eud_attrs[0]);
> +
> +	return ret;
> +}
> +
> +static int eud_remove(struct platform_device *pdev)
> +{
> +	struct eud_chip *chip = platform_get_drvdata(pdev);
> +
> +	if (chip->enable)
> +		disable_eud(chip);
> +
> +	device_remove_file(&pdev->dev, eud_attrs[0]);
> +	device_init_wakeup(&pdev->dev, false);
> +	disable_irq_wake(chip->eud_irq);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id eud_dt_match[] = {
> +	{ .compatible = "qcom,usb-connector-eud" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, eud_dt_match);
> +
> +static struct platform_driver eud_driver = {
> +	.probe		= eud_probe,
> +	.remove		= eud_remove,
> +	.driver		= {
> +		.name		= "eud",
> +		.of_match_table = eud_dt_match,
> +	},
> +};
> +module_platform_driver(eud_driver);
> +
> +MODULE_DESCRIPTION("QTI EUD driver");
> +MODULE_LICENSE("GPL v2");
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
> 

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