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

Bjorn Andersson
2022-01-07T01:18:22Z

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?

> +#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.

> + void __iomem *eud_mode_mgr2_phys_base;

"mode_mgr"

> + unsigned int int_status;
> + int eud_irq;

"irq"

> + bool enable;

"enable" is an action, but you use it to track if the state of the EUD,
i.e if it's "enabled".

> + bool usb_attach;

"attach" vs "attached"

> +

Empty line.

> +};
> +
> +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?

> +}
> +
> +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;

> +
> + /* 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?

> +}
> +
> +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.
*/

> + reg = readl(chip->eud_reg_base + EUD_REG_SW_ATTACH_DET);

Please drop the double space.

> + 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?

> + } 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.

> + reg = readl(chip->eud_reg_base + EUD_REG_INT_STATUS_1);

Please drop the double space.

> + 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?

> + 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.

> + 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.

> + 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?

> + 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);

> +
> + 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.

> + .remove = eud_remove,
> + .driver = {
> + .name = "eud",

"qcom_eud" please.

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
>