Message-ID: <c072d162-e371-e44b-8160-d06a8a6c051c@quicinc.com>
Date:   Thu, 27 Jan 2022 17:31:11 +0530
From:   Souradeep Chowdhury <quic_schowdhu@...cinc.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <pure.logic@...us-software.ie>,
        <greg@...ah.com>, <robh@...nel.org>,
        <linux-kernel@...r.kernel.org>, <quic_tsoni@...cinc.com>,
        <quic_psodagud@...cinc.com>, <quic_satyap@...cinc.com>,
        <quic_pheragu@...cinc.com>, <quic_rjendra@...cinc.com>,
        <quic_sibis@...cinc.com>, <quic_saipraka@...cinc.com>
Subject: Re: [PATCH V4 3/6] soc: qcom: eud: Add driver support for Embedded
 USB Debugger(EUD)


On 1/26/2022 10:17 AM, Bjorn Andersson wrote:
> On Fri 21 Jan 07:53 CST 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@...cinc.com>
>> ---
>>   Documentation/ABI/testing/sysfs-driver-eud |   9 ++
>>   drivers/soc/qcom/Kconfig                   |  10 ++
>>   drivers/soc/qcom/Makefile                  |   1 +
>>   drivers/soc/qcom/qcom_eud.c                | 250 +++++++++++++++++++++++++++++
>>   4 files changed, 270 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 <quic_schowdhu@...cinc.com>
>> +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 e718b87..abc6be0 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"
> The indentation looks off here.
Ack
>
>> +	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 70d5de6..e0c7d2d 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..a538645
>> --- /dev/null
>> +++ b/drivers/soc/qcom/qcom_eud.c
>> @@ -0,0 +1,250 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
>> + */
>> +
>> +#include <linux/bitops.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			*base;
>> +	void __iomem			*mode_mgr;
>> +	unsigned int			int_status;
>> +	int				irq;
>> +	bool				enabled;
>> +	bool				usb_attached;
>> +};
>> +
>> +static int enable_eud(struct eud_chip *priv)
>> +{
>> +	writel(EUD_ENABLE, priv->base + EUD_REG_CSR_EUD_EN);
>> +	writel(EUD_INT_VBUS | EUD_INT_SAFE_MODE,
>> +			priv->base + EUD_REG_INT1_EN_MASK);
>> +	writel(1, priv->mode_mgr + EUD_REG_EUD_EN2);
>> +
>> +	return usb_role_switch_set_role(priv->role_sw, USB_ROLE_DEVICE);
> So we won't get EUD_INT_VBUS when we enable the EUD and can rely on the
> irq handler to set the role?

Yes, in this case it is being explicitly set based on the user input 
rather than through irq handler.

In this way we are able to detect if the role is set properly and take 
the next steps from the

enable_store method.

>
>> +}
>> +
>> +static void disable_eud(struct eud_chip *priv)
>> +{
>> +	writel(0, priv->base + EUD_REG_CSR_EUD_EN);
>> +	writel(0, priv->mode_mgr + 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->enabled);
>> +}
>> +
>> +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->enabled = enable;
>> +		else
>> +			disable_eud(chip);
>> +	} 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->base + EUD_REG_CTL_OUT_1);
>> +	chip->usb_attached = reg & EUD_INT_SAFE_MODE;
>> +}
>> +
>> +static void pet_eud(struct eud_chip *chip)
>> +{
>> +	u32 reg;
>> +	int ret;
>> +
>> +	/* When the EUD_INT_PET_EUD in SW_ATTACH_DET is set, the cable has been
>> +	 * disconnected and we need to detach the pet to check if EUD is in safe
>> +	 * mode before attaching again.
>> +	 */
>> +	reg = readl(chip->base + EUD_REG_SW_ATTACH_DET);
>> +	if (reg & EUD_INT_PET_EUD) {
>> +		/* Detach & Attach pet for EUD */
>> +		writel(0, chip->base + EUD_REG_SW_ATTACH_DET);
>> +		/* Delay to make sure detach pet is done before attach pet */
>> +		ret = readl_poll_timeout(chip->base + EUD_REG_SW_ATTACH_DET,
>> +					reg, (reg == 0), 1, 100);
>> +		if (ret) {
>> +			dev_err(chip->dev, "Detach pet failed\n");
>> +			return;
>> +		}
>> +	}
>> +	/* Attach pet for EUD */
>> +	writel(EUD_INT_PET_EUD, chip->base +EUD_REG_SW_ATTACH_DET);
>> +}
>> +
>> +static irqreturn_t handle_eud_irq(int irq, void *data)
>> +{
>> +	struct eud_chip *chip = data;
>> +	u32 reg;
>> +
>> +	reg = readl(chip->base + EUD_REG_INT_STATUS_1);
>> +	switch (reg & EUD_INT_ALL) {
>> +	case EUD_INT_VBUS:
>> +		chip->int_status = EUD_INT_VBUS;
> The first time that reg & EUD_INT_VBUS is set, you assign int_status
> EUD_INT_VBUS, you never clear it again.
>
> This is also the only path where you wake up the thread, so int_status
> will always be EUD_INT_VBUS when you reach handle_eud_irq_thread().
>
> Which means that int_status serves no purpose and if you're happy with
> how this implementation currently works you can just drop "int_status"
> and the conditional below.
Ack. Will remove the int_status flag as it is not needed.
>
>> +		usb_attach_detach(chip);
>> +		return IRQ_WAKE_THREAD;
>> +	case EUD_INT_SAFE_MODE:
>> +		pet_eud(chip);
>> +		return IRQ_HANDLED;
>> +	default:
>> +		return IRQ_NONE;
>> +	}
>> +}
>> +
>> +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_attached)
>> +			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");
>> +	}
>> +
>> +	/* set and clear vbus_int_clr[0] to clear interrupt */
>> +	writel(BIT(0), chip->base + EUD_REG_VBUS_INT_CLR);
>> +	writel(0, chip->base + EUD_REG_VBUS_INT_CLR);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int eud_probe(struct platform_device *pdev)
>> +{
>> +	struct eud_chip *chip;
>> +	struct fwnode_handle *fwnode = pdev->dev.fwnode, *dwc3;
>> +	int ret;
>> +
>> +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
>> +	if (!chip)
>> +		return -ENOMEM;
>> +
>> +	chip->dev = &pdev->dev;
>> +
>> +	dwc3 = fwnode_graph_get_next_endpoint(fwnode, NULL);
> This will pick the first endpoint, but if you instead use
>
>      chip->role_sw = usb_role_switch_get(&pdev->dev);
>
> you should get whichever port that points to a usb-role-switch node,
> without having to do the fwnode dance (and refcounting, which you forgot
> to release).
Ack
>
>> +	if (!dwc3)
>> +		return -ENODEV;
>> +
>> +	chip->role_sw = fwnode_usb_role_switch_get(dwc3);
>> +	if (IS_ERR(chip->role_sw)) {
>> +		ret = PTR_ERR(chip->role_sw);
>> +		usb_role_switch_put(chip->role_sw);
> You don't need to return the role_sw if it's IS_ERR().
Ack
>
>> +		return dev_err_probe(chip->dev, ret,
>> +					"failed to get role switch\n");
>> +	}
>> +
>> +	chip->base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(chip->base))
> You're not usb_role_switch_put() your role_sw here, or below return
> cases. I would recommend devm_add_action_or_reset() to avoid the hassle
> of adding the necessary cleanup logic.
Ack
>
>> +		return PTR_ERR(chip->base);
>> +
>> +	chip->mode_mgr = devm_platform_ioremap_resource(pdev, 1);
>> +	if (IS_ERR(chip->mode_mgr))
>> +		return PTR_ERR(chip->mode_mgr);
>> +
>> +	chip->irq = platform_get_irq(pdev, 0);
>> +	ret = devm_request_threaded_irq(&pdev->dev, chip->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->irq);
>> +
>> +	platform_set_drvdata(pdev, chip);
>> +
>> +	return 0;
> Per the updated binding, the EUD would now be a usb-role-switch as well
> and when not enabled should simply propagate the incoming requests. So I
> was expecting this to register as a usb_role_switch as well...

Can you please elaborate on this?

Do I need to define a separate 'usb_role_switch_desc' here and register 
using 'usb_role_switch_register'?

Also what should be the set method in this case for usb_role_switch_desc?

>
>> +}
>> +
>> +static int eud_remove(struct platform_device *pdev)
>> +{
>> +	struct eud_chip *chip = platform_get_drvdata(pdev);
>> +
>> +	if (chip->enabled)
>> +		disable_eud(chip);
>> +
>> +	device_init_wakeup(&pdev->dev, false);
>> +	disable_irq_wake(chip->irq);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id eud_dt_match[] = {
>> +	{ .compatible = "qcom,sc7280-eud" },
> Do you see any reason for not just adding qcom,eud here? Are there any
> differences from other platforms that has this block that means that we
> need per-platform driver support (the dts should have both
> compatibles still)?
That is correct, this might need driver support for multiple platforms.
>
> Regards,
> Bjorn
>
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, eud_dt_match);
>> +
>> +static struct platform_driver eud_driver = {
>> +	.probe	= eud_probe,
>> +	.remove	= eud_remove,
>> +	.driver	= {
>> +		.name = "qcom_eud",
>> +		.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
>>

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