Date:   Mon, 4 Sep 2017 13:19:26 +0200
From:   Peter Rosin <peda@...ator.liu.se>
To:     Hans de Goede <hdegoede@...hat.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Mathias Nyman <mathias.nyman@...el.com>
Cc:     platform-driver-x86@...r.kernel.org, devel@...verdev.osuosl.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy Natarajan <sathyaosid@...il.com>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 05/11] mux: Add Intel Cherrytrail USB mux driver

Hi!

Some comments inline...

On 2017-09-01 23:48, Hans de Goede wrote:
> Intel Cherrytrail SoCs have an internal USB mux for muxing the otg-port
> USB data lines between the xHCI host controller and the dwc3 gadget
> controller. On some Cherrytrail systems this mux is controlled through
> AML code reacting on a GPIO IRQ connected to the USB OTG id pin (through
> an _AIE ACPI method) so things just work.
> 
> But on other Cherrytrail systems we need to control the mux ourselves
> this driver exports the mux through the mux subsys, so that other drivers
> can control it if necessary.
> 
> This driver also updates the vbus-valid reporting to the dwc3 gadget
> controller, as this uses the same registers as the mux. This is needed
> for gadget/device mode to work properly (even on systems which control
> the mux from their AML code).
> 
> Note this depends on the xhci driver registering a platform device
> named "intel_cht_usb_mux", which has an IOMEM resource 0 which points
> to the Intel Vendor Defined XHCI extended capabilities region.
> 
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---
> Changes in v2:
> -Complete rewrite as a stand-alone platform-driver rather then as a phy
>  driver, since this is just a mux, not a phy
> 
> Changes in v3:
> -Make this a mux subsys driver instead of listening to USB_HOST extcon
>  cable events and responding to those
> ---
>  drivers/mux/Kconfig             |  11 ++
>  drivers/mux/Makefile            |   2 +
>  drivers/mux/intel_cht_usb_mux.c | 269 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 282 insertions(+)
>  create mode 100644 drivers/mux/intel_cht_usb_mux.c
> 
> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> index 19e4e904c9bf..17938918bf93 100644
> --- a/drivers/mux/Kconfig
> +++ b/drivers/mux/Kconfig
> @@ -34,6 +34,17 @@ config MUX_GPIO
>  	  To compile the driver as a module, choose M here: the module will
>  	  be called mux-gpio.
>  
> +config MUX_CHT_USB_MUX
> +	tristate "Intel Cherrytrail USB Multiplexer"
> +	depends on ACPI && X86 && EXTCON
> +	help
> +	  This driver adds support for the internal USB mux for muxing the OTG
> +	  USB data lines between the xHCI host controller and the dwc3 gadget
> +	  controller found on Intel Cherrytrail SoCs.
> +
> +	  To compile the driver as a module, choose M here: the module will
> +	  be called mux-intel_cht_usb_mux.
> +
>  config MUX_MMIO
>  	tristate "MMIO register bitfield-controlled Multiplexer"
>  	depends on (OF && MFD_SYSCON) || COMPILE_TEST
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index 0e1e59760e3f..a12e812c7966 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -6,8 +6,10 @@ mux-core-objs			:= core.o
>  mux-adg792a-objs		:= adg792a.o
>  mux-gpio-objs			:= gpio.o
>  mux-mmio-objs			:= mmio.o
> +mux-intel_cht_usb_mux-objs	:= intel_cht_usb_mux.o

I dislike underscores in file names (and other names), please use
dashes where possible. Also, please keep the list sorted.

>  
>  obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
>  obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
>  obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
>  obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o
> +obj-$(CONFIG_MUX_CHT_USB_MUX)	+= mux-intel_cht_usb_mux.o

Dito.

> diff --git a/drivers/mux/intel_cht_usb_mux.c b/drivers/mux/intel_cht_usb_mux.c
> new file mode 100644
> index 000000000000..7b1621a081d8
> --- /dev/null
> +++ b/drivers/mux/intel_cht_usb_mux.c
> @@ -0,0 +1,269 @@
> +/*
> + * Intel Cherrytrail USB OTG MUX driver
> + *
> + * Copyright (c) 2016 Hans de Goede <hdegoede@...hat.com>
> + *
> + * Loosely based on android x86 kernel code which is:
> + *
> + * Copyright (C) 2014 Intel Corp.
> + *
> + * Author: Wu, Hao
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation, or (at your option)
> + * any later version.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/extcon.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mux/consumer.h> /* For the MUX_USB_* defines */
> +#include <linux/mux/driver.h>
> +#include <linux/platform_device.h>
> +#include <linux/workqueue.h>
> +
> +/* register definition */
> +#define DUAL_ROLE_CFG0			0x68
> +#define SW_VBUS_VALID			(1 << 24)
> +#define SW_IDPIN_EN			(1 << 21)
> +#define SW_IDPIN			(1 << 20)
> +
> +#define DUAL_ROLE_CFG1			0x6c
> +#define HOST_MODE			(1 << 29)
> +
> +#define DUAL_ROLE_CFG1_POLL_TIMEOUT	1000
> +
> +#define DRV_NAME			"intel_cht_usb_mux"

Dashes, please, if possible. Or are there perhaps a lot of precedent
for other cherrytrail driver names? Because consistency across
the tree is a tad more important than my issues with underscores...

> +
> +struct intel_cht_usb_mux {
> +	struct mutex cfg0_lock;
> +	void __iomem *base;
> +	struct extcon_dev *vbus_extcon;
> +	struct notifier_block vbus_nb;
> +	struct work_struct vbus_work;
> +};
> +
> +struct intel_cht_extcon_info {
> +	const char *hid;
> +	int hrv;
> +	const char *extcon;
> +};
> +
> +struct intel_cht_extcon_info vbus_providers[] = {
> +	{ "INT33F4", -1, "axp288_extcon" },
> +	{ "INT34D3",  3, "cht_wcove_pwrsrc" },
> +};

Dito. And static const. What about:

static const struct intel_cht_extcon_info vbus_providers[] = {
	{ .hid = "INT33F4", .hrv = -1, .extcon = "axp288_extcon", },
	{ .hid = "INT34D3", .hrv =  3, .extcon = "cht_wcove_pwrsrc", },
};

> +
> +static const unsigned int vbus_cable_ids[] = {
> +	EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP,
> +	EXTCON_CHG_USB_ACA, EXTCON_CHG_USB_FAST,
> +};
> +
> +static void intel_cht_usb_mux_set_sw_mode(struct intel_cht_usb_mux *mux)
> +{
> +	u32 data;
> +
> +	data = readl(mux->base + DUAL_ROLE_CFG0);
> +	if (!(data & SW_IDPIN_EN)) {
> +		data |= SW_IDPIN_EN;
> +		writel(data, mux->base + DUAL_ROLE_CFG0);
> +	}
> +}

Is SW_IDPIN_EN a bit that unlocks the other bits in the register for
writing? Once? Perhaps it interacts with the mode switch confirmation
loop? Anyway, I'd like to see a comment about why this bit needs to be
set so many times.

> +
> +static int intel_cht_usb_mux_set_mux(struct mux_control *mux_ctrl, int state)
> +{
> +	struct intel_cht_usb_mux *mux = mux_chip_priv(mux_ctrl->chip);

The "mux" variable name is used for the mux_control in other drivers, and
the private data is named something else. Please fix this all over the
driver for consistency across the subsys.

> +	unsigned long timeout;
> +	bool host_mode;
> +	u32 data;
> +
> +	mutex_lock(&mux->cfg0_lock);
> +
> +	intel_cht_usb_mux_set_sw_mode(mux);
> +
> +	/* Set idpin value as requested */
> +	data = readl(mux->base + DUAL_ROLE_CFG0);
> +	switch (state & ~MUX_USB_POLARITY_INV) {
> +	case MUX_USB_NONE:
> +	case MUX_USB_DEVICE:
> +		data |= SW_IDPIN;
> +		host_mode = false;
> +		break;
> +	default:
> +		data &= ~SW_IDPIN;
> +		host_mode = true;
> +	}
> +	writel(data, mux->base + DUAL_ROLE_CFG0);
> +
> +	mutex_unlock(&mux->cfg0_lock);
> +
> +	/* In most case it takes about 600ms to finish mode switching */
> +	timeout = jiffies + msecs_to_jiffies(DUAL_ROLE_CFG1_POLL_TIMEOUT);
> +
> +	/* Polling on CFG1 register to confirm mode switch.*/
> +	while (1) {
> +		data = readl(mux->base + DUAL_ROLE_CFG1);
> +		if (!!(data & HOST_MODE) == host_mode)
> +			break;
> +
> +		/* Interval for polling is set to about 5 - 10 ms */
> +		usleep_range(5000, 10000);
> +
> +		if (time_after(jiffies, timeout)) {
> +			dev_warn(&mux_ctrl->chip->dev,
> +				 "Timeout waiting for mux to switch\n");
> +			break;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void intel_cht_usb_mux_set_vbus_valid(struct intel_cht_usb_mux *mux,
> +					     bool valid)
> +{
> +	u32 data;
> +
> +	mutex_lock(&mux->cfg0_lock);
> +
> +	intel_cht_usb_mux_set_sw_mode(mux);
> +
> +	data = readl(mux->base + DUAL_ROLE_CFG0);
> +	if (valid)
> +		data |= SW_VBUS_VALID;
> +	else
> +		data &= ~SW_VBUS_VALID;
> +	writel(data, mux->base + DUAL_ROLE_CFG0);
> +
> +	mutex_unlock(&mux->cfg0_lock);
> +}
> +
> +static void intel_cht_usb_mux_vbus_work(struct work_struct *work)
> +{
> +	struct intel_cht_usb_mux *mux =
> +		container_of(work, struct intel_cht_usb_mux, vbus_work);
> +	bool vbus_present = false;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(vbus_cable_ids); i++) {
> +		if (extcon_get_state(mux->vbus_extcon, vbus_cable_ids[i]) > 0) {
> +			vbus_present = true;
> +			break;
> +		}
> +	}
> +
> +	intel_cht_usb_mux_set_vbus_valid(mux, vbus_present);
> +}
> +
> +static int intel_cht_usb_mux_vbus_extcon_evt(struct notifier_block *nb,
> +					     unsigned long event, void *param)
> +{
> +	struct intel_cht_usb_mux *mux =
> +		container_of(nb, struct intel_cht_usb_mux, vbus_nb);
> +
> +	schedule_work(&mux->vbus_work);
> +
> +	return NOTIFY_OK;
> +}
> +
> +static const struct mux_control_ops intel_cht_usb_mux_ops = {
> +	.set = intel_cht_usb_mux_set_mux,
> +};
> +
> +static int intel_cht_usb_mux_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct intel_cht_usb_mux *mux;
> +	struct mux_chip *mux_chip;
> +	struct resource *res;
> +	resource_size_t size;
> +	int i, ret;
> +
> +	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux));
> +	if (IS_ERR(mux_chip))
> +		return PTR_ERR(mux_chip);
> +
> +	mux_chip->ops = &intel_cht_usb_mux_ops;
> +	mux_chip->mux[0].states = MUX_USB_STATES;

This is "a lie" I think, the mux only supports two states; device and host.

Looks good otherwise, if you also consider the remarks from Andy.

Cheers,
Peter

> +	mux = mux_chip_priv(mux_chip);
> +	mutex_init(&mux->cfg0_lock);
> +
> +	/*
> +	 * Besides controlling the mux we also need to control the vbus_valid
> +	 * flag for device/gadget mode to work properly. To do this we monitor
> +	 * the extcon interface exported by the PMIC drivers for the PMICs used
> +	 * with the Cherry Trail SoC.
> +	 *
> +	 * We try to get the extcon_dev before registering the mux as this
> +	 * may lead to us exiting with -EPROBE_DEFER.
> +	 */
> +	for (i = 0 ; i < ARRAY_SIZE(vbus_providers); i++) {
> +		if (!acpi_dev_present(vbus_providers[i].hid, NULL,
> +				      vbus_providers[i].hrv))
> +			continue;
> +
> +		mux->vbus_extcon = extcon_get_extcon_dev(
> +						vbus_providers[i].extcon);
> +		if (mux->vbus_extcon == NULL)
> +			return -EPROBE_DEFER;
> +
> +		dev_info(dev, "using extcon '%s' for vbus-valid\n",
> +			 vbus_providers[i].extcon);
> +		break;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	size = (res->end + 1) - res->start;
> +	mux->base = devm_ioremap_nocache(dev, res->start, size);
> +	if (IS_ERR(mux->base)) {
> +		ret = PTR_ERR(mux->base);
> +		dev_err(dev, "can't iomap registers: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = devm_mux_chip_register(dev, mux_chip);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (mux->vbus_extcon) {
> +		INIT_WORK(&mux->vbus_work, intel_cht_usb_mux_vbus_work);
> +		mux->vbus_nb.notifier_call = intel_cht_usb_mux_vbus_extcon_evt;
> +		ret = devm_extcon_register_notifier_all(dev, mux->vbus_extcon,
> +							&mux->vbus_nb);
> +		if (ret) {
> +			dev_err(dev, "can't register vbus extcon notifier: %d\n",
> +				ret);
> +			return ret;
> +		}
> +
> +		/* Sync initial mode */
> +		schedule_work(&mux->vbus_work);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct platform_device_id intel_cht_usb_mux_table[] = {
> +	{ .name = DRV_NAME },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(platform, intel_cht_usb_mux_table);
> +
> +static struct platform_driver intel_cht_usb_mux_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +	},
> +	.id_table = intel_cht_usb_mux_table,
> +	.probe = intel_cht_usb_mux_probe,
> +};
> +
> +module_platform_driver(intel_cht_usb_mux_driver);
> +
> +MODULE_AUTHOR("Hans de Goede <hdegoede@...hat.com>");
> +MODULE_DESCRIPTION("Intel Cherrytrail USB mux driver");
> +MODULE_LICENSE("GPL");
> 

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