[V3,4/7] soc: qcom: eud: Add driver support for Embedded USB Debugger(EUD)

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 <quic_schowdhu@quicinc.com>
---
 Documentation/ABI/testing/sysfs-driver-eud |   9 +
 drivers/soc/qcom/Kconfig                   |  10 ++
 drivers/soc/qcom/Makefile                  |   1 +
 drivers/soc/qcom/qcom_eud.c                | 260 +++++++++++++++++++++++++++++
 4 files changed, 280 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-eud
 create mode 100644 drivers/soc/qcom/qcom_eud.c

On 1/7/2022 6:49 AM, Bjorn Andersson wrote:
> On Tue 04 Jan 03:58 PST 2022, 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 <quic_schowdhu@quicinc.com>
>> ---
>>   Documentation/ABI/testing/sysfs-driver-eud |   9 +
>>   drivers/soc/qcom/Kconfig                   |  10 ++
>>   drivers/soc/qcom/Makefile                  |   1 +
>>   drivers/soc/qcom/qcom_eud.c                | 260 +++++++++++++++++++++++++++++
>>   4 files changed, 280 insertions(+)
>>   create mode 100644 Documentation/ABI/testing/sysfs-driver-eud
>>   create mode 100644 drivers/soc/qcom/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..2381552
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-driver-eud
>> @@ -0,0 +1,9 @@
>> +What:		/sys/bus/platform/drivers/eud/.../enable
>> +Date:           January 2022
>> +Contact:        Souradeep Chowdhury <schowdhu@codeaurora.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. By enabling EUD,
>> +		the user is able to activate the mini-usb hub of
>> +		EUD for debug and trace capabilities.
>> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
>> index 79b568f..a4db41b 100644
>> --- a/drivers/soc/qcom/Kconfig
>> +++ b/drivers/soc/qcom/Kconfig
>> @@ -42,6 +42,16 @@ config QCOM_CPR
>>   	  To compile this driver as a module, choose M here: the module will
>>   	  be called qcom-cpr
>>   
>> +config QCOM_EUD
>> +	tristate "QCOM Embedded USB Debugger(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. On selecting m, the module name
>> +	  that is built is qcom_eud.ko
>> +
>>   config QCOM_GENI_SE
>>   	tristate "QCOM GENI Serial Engine Driver"
>>   	depends on ARCH_QCOM || COMPILE_TEST
>> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
>> index ad675a6..3331a40 100644
>> --- a/drivers/soc/qcom/Makefile
>> +++ b/drivers/soc/qcom/Makefile
>> @@ -4,6 +4,7 @@ obj-$(CONFIG_QCOM_AOSS_QMP) +=	qcom_aoss.o
>>   obj-$(CONFIG_QCOM_GENI_SE) +=	qcom-geni-se.o
>>   obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o
>>   obj-$(CONFIG_QCOM_CPR)		+= cpr.o
>> +obj-$(CONFIG_QCOM_EUD)          += qcom_eud.o
>>   obj-$(CONFIG_QCOM_GSBI)	+=	qcom_gsbi.o
>>   obj-$(CONFIG_QCOM_MDT_LOADER)	+= mdt_loader.o
>>   obj-$(CONFIG_QCOM_OCMEM)	+= ocmem.o
>> diff --git a/drivers/soc/qcom/qcom_eud.c b/drivers/soc/qcom/qcom_eud.c
>> new file mode 100644
>> index 0000000..7c4cc7d
>> --- /dev/null
>> +++ b/drivers/soc/qcom/qcom_eud.c
>> @@ -0,0 +1,260 @@
>> +// 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>
> Is this needed?
Ack.
>
>> +#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;
> This is unnecessarily long, "base" or "eud" seems sufficient.
Ack
>
>> +	void __iomem			*eud_mode_mgr2_phys_base;
> "mode_mgr"
Ack
>
>> +	unsigned int			int_status;
>> +	int				eud_irq;
> "irq"
Ack
>
>> +	bool				enable;
> "enable" is an action, but you use it to track if the state of the EUD,
> i.e if it's "enabled".
Ack
>
>> +	bool				usb_attach;
> "attach" vs "attached"
Ack
>
>> +
> Empty line.
Ack
>
>> +};
>> +
>> +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);
> When this fails, don't you want to disable the EUD again?
Ack
>
>> +}
>> +
>> +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 sysfs_emit(buf, "%d\n", 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);
>> +	bool enable;
>> +	int ret;
>> +
>> +	if (kstrtobool(buf, &enable))
>> +		return -EINVAL;
>> +
>> +	if (enable) {
>> +		ret = enable_eud(chip);
>> +		if (!ret)
>> +			chip->enable = enable;
>> +	} else {
>> +		disable_eud(chip);
>> +	}
>> +
>> +	return count;
>> +}
>> +
>> +static DEVICE_ATTR_RW(enable);
>> +
>> +static struct attribute *eud_attrs[] = {
>> +	&dev_attr_enable.attr,
>> +	NULL,
>> +};
>> +ATTRIBUTE_GROUPS(eud);
>> +
>> +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;
> chip->usb_attach = reg & EUD_INT_SAFE_MODE;
Ack
>> +
>> +	/* 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);
> How come you do this before waking up the threaded handler?
Ack
>
>> +}
>> +
>> +static void pet_eud(struct eud_chip *chip)
>> +{
>> +	u32 reg;
>> +	int ret;
>> +
>> +	/* read sw_attach_det[0] to find attach/detach event */
> Please instead describe what this means, like:
>
> /*
>   * When the EUD_INT_PET_EUD in SW_ATTACH_DET is set, the cable has been
>   * disconnected and we need to detach the something because something.
>   */
Ack
>
>> +	reg = readl(chip->eud_reg_base +  EUD_REG_SW_ATTACH_DET);
> Please drop the double space.
Ack
>
>> +	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);
> Can you please help me see what differs between this and the write in
> the else statement?

Ack. Will move this out of the if else statement.

>
>> +	} 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 */
> That's what the next line says as well, please drop this comment.
Ack
>
>> +	reg = readl(chip->eud_reg_base +  EUD_REG_INT_STATUS_1);
> Please drop the double space.
Ack
>
>> +	switch (reg & EUD_INT_ALL) {
> What if both of these bits are set? Won't you just end up with an
> interrupt storm until someone disables the EUD again?
So EUD can either be in safe mode or vbus mode ,  both bits will not be 
set together.
>
>> +	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;
> This is the only case where you break to return IRQ_HANDLED. Please be
> consistent.
Ack
>
>> +	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) {
> I presume you have this here to signal that EUD_INT_VBUS was set in
> EUD_REG_INT_STATUS_1 in handle_eud_irq().
>
> But 1) unless this was true you wouldn't have woken up the threaded
> handler and 2) you never clear int_status, so once you've received the
> EUD_INT_VBUS it seems to forever be true.
Ack. Will be clearing the int bits once this is done.
>
>> +		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);
>> +		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;
>> +	struct fwnode_handle *fwnode = pdev->dev.fwnode, *ep, *connector;
>> +	int ret;
>> +
>> +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
>> +	if (!chip)
>> +		return -ENOMEM;
>> +
>> +	chip->dev = &pdev->dev;
>> +
>> +	ep = fwnode_graph_get_next_endpoint(fwnode, NULL);
>> +	if (!ep)
>> +		return -ENODEV;
>> +
>> +	connector = fwnode_graph_get_remote_port_parent(ep);
>> +	fwnode_handle_put(ep);
>> +	if (!connector)
>> +		return -ENODEV;
>> +
>> +	chip->role_sw = fwnode_usb_role_switch_get(connector);
> Can't you just call usb_role_switch_get(&pdev->dev) to find the
> "usb-role-switch", without having to traverse the fwnode_graph manually?

"usb_role_switch_get" finds the role_switch from the current or the 
parent node, however

in this case the usb-role-switch property is present at the parent of 
the connector node

which is attached to the eud node via port end point.

>
>> +	if (IS_ERR(chip->role_sw)) {
>> +		return dev_err_probe(chip->dev, PTR_ERR(chip->role_sw),
>> +					"failed to get role switch\n");
>> +	}
> Note that from now on you must usb_role_switch_put(chip->role_sw);
Ack
>
>> +
>> +	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)
>> +		return dev_err_probe(chip->dev, ret, "failed to allocate irq\n");
>> +
>> +	enable_irq_wake(chip->eud_irq);
>> +
>> +	platform_set_drvdata(pdev, chip);
>> +
>> +	return 0;
>> +}
>> +
>> +static int eud_remove(struct platform_device *pdev)
>> +{
>> +	struct eud_chip *chip = platform_get_drvdata(pdev);
>> +
>> +	if (chip->enable)
>> +		disable_eud(chip);
>> +
>> +	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,sc7280-eud" },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, eud_dt_match);
>> +
>> +static struct platform_driver eud_driver = {
>> +	.probe		= eud_probe,
> I would prefer if you didn't indent the assignments.
Ack
>
>> +	.remove		= eud_remove,
>> +	.driver		= {
>> +		.name		= "eud",
> "qcom_eud" please.
Ack
>
> Regards,
> Bjorn
>
>> +		.dev_groups	= eud_groups,
>> +		.of_match_table = eud_dt_match,
>> +	},
>> +};
>> +module_platform_driver(eud_driver);
>> +
>> +MODULE_DESCRIPTION("QTI EUD driver");
>> +MODULE_LICENSE("GPL v2");
>> -- 
>> 2.7.4
>>