From: "myungjoo.ham" <myungjoo.ham@samsung.com>
To: "'Kishon Vijay Abraham I'" <kishon@ti.com>, cw00.choi@samsung.com,
        balbi@ti.com, ldewangan@nvidia.com,
        devicetree-discuss@lists.ozlabs.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc: grant.likely@linaro.org, rob.herring@calxeda.com, rob@landley.net,
        gg@slimlogic.co.uk, ruchika@ti.com, tony@atomide.com,
        sameo@linux.intel.com, broonie@opensource.wolfsonmicro.com
References: <1362662506-14823-4-git-send-email-kishon@ti.com>
 <1367846225-15685-1-git-send-email-kishon@ti.com>
In-reply-to: <1367846225-15685-1-git-send-email-kishon@ti.com>
Subject: RE: [PATCH v4] extcon: Palmas Extcon Driver
Date: Tue, 07 May 2013 09:43:10 +0900
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> From: Graeme Gregory <gg@slimlogic.co.uk>
> 
> This is the driver for the USB comparator built into the palmas chip. It
> handles the various USB OTG events that can be generated by cable
> insertion/removal.
> 
> Signed-off-by: Graeme Gregory <gg@slimlogic.co.uk>
> Signed-off-by: Moiz Sonasath <m-sonasath@ti.com>
> Signed-off-by: Ruchika Kharwar <ruchika@ti.com>
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> [kishon@ti.com: adapted palmas usb driver to use the extcon framework]
> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>

Here goes some comments in the code:

[]

> diff --git a/drivers/extcon/extcon-palmas.c
b/drivers/extcon/extcon-palmas.c
> new file mode 100644
> index 0000000..3ef042f
> --- /dev/null
> +++ b/drivers/extcon/extcon-palmas.c
> @@ -0,0 +1,389 @@
> +/*
> + * Palmas USB transceiver driver
> + *
> + * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * Author: Graeme Gregory <gg@...mlogic.co.uk>
> + * Author: Kishon Vijay Abraham I <kishon@...com>
> + *
> + * Based on twl6030_usb.c
> + *
> + * Author: Hema HK <hemahk@...com>
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */

Why the email addresses are masked in the source code?
(I'm just curious as this is the first time to see such in kernel source)

> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/platform_device.h>
> +#include <linux/io.h>
> +#include <linux/usb/phy_companion.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/err.h>
> +#include <linux/notifier.h>
> +#include <linux/slab.h>
> +#include <linux/delay.h>
> +#include <linux/mfd/palmas.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/extcon/extcon_palmas.h>
> +
> +static const char *palmas_extcon_cable[] = {
> +	[0] = "USB",
> +	[1] = "USB-HOST",

	[1] = "USB-Host",

> +	NULL,
> +};
> +
> +static const int mutually_exclusive[] = {0x3, 0x0};
> +
> +static void palmas_usb_wakeup(struct palmas *palmas, int enable)
> +{
> +	if (enable)
> +		palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP,
> +			PALMAS_USB_WAKEUP_ID_WK_UP_COMP);
> +	else
> +		palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP,
0);
> +}
> +
> +static ssize_t palmas_usb_vbus_show(struct device *dev,
> +			struct device_attribute *attr, char *buf)
> +{
> +	unsigned long		flags;
> +	int			ret = -EINVAL;
> +	struct palmas_usb	*palmas_usb = dev_get_drvdata(dev);
> +
> +	spin_lock_irqsave(&palmas_usb->lock, flags);

This spinlock is used in this sysfs-show function only.
Is this really needed?
The only protected value here is "linkstat", which is "readonly"
in this protected context.
Thus, removing the spin_lock and updating like the following should
be the same with less overhead:

	int linkstat = palmas_usb->linkstat;
	switch(linkstat) {


> +
> +	switch (palmas_usb->linkstat) {
> +	case PALMAS_USB_STATE_VBUS:
> +	       ret = snprintf(buf, PAGE_SIZE, "vbus\n");
> +	       break;
> +	case PALMAS_USB_STATE_ID:
> +	       ret = snprintf(buf, PAGE_SIZE, "id\n");
> +	       break;
> +	case PALMAS_USB_STATE_DISCONNECT:
> +	       ret = snprintf(buf, PAGE_SIZE, "none\n");
> +	       break;
> +	default:
> +	       ret = snprintf(buf, PAGE_SIZE, "UNKNOWN\n");
> +	}
> +	spin_unlock_irqrestore(&palmas_usb->lock, flags);
> +
> +	return ret;
> +}
> +static DEVICE_ATTR(vbus, 0444, palmas_usb_vbus_show, NULL);
> +

[]

> +
> +static void palmas_set_vbus_work(struct work_struct *data)
> +{
> +	int ret;
> +	struct palmas_usb *palmas_usb = container_of(data, struct
palmas_usb,
> +
set_vbus_work);
> +
> +	if (IS_ERR_OR_NULL(palmas_usb->vbus_reg)) {
> +		dev_err(palmas_usb->dev, "invalid regulator\n");
> +		return;
> +	}
> +
> +	/*
> +	 * Start driving VBUS. Set OPA_MODE bit in CHARGERUSB_CTRL1
> +	 * register. This enables boost mode.
> +	 */
> +
> +	if (palmas_usb->vbus_enable) {
> +		ret = regulator_enable(palmas_usb->vbus_reg);
> +		if (ret)
> +			dev_dbg(palmas_usb->dev, "regulator enable
failed\n");
> +	} else {
> +		regulator_disable(palmas_usb->vbus_reg);
> +	}
> +}
> +
> +static int palmas_set_vbus(struct phy_companion *comparator, bool
enabled)
> +{
> +	struct palmas_usb *palmas_usb = comparator_to_palmas(comparator);
> +
> +	palmas_usb->vbus_enable = enabled;
> +	schedule_work(&palmas_usb->set_vbus_work);
> +
> +	return 0;
> +}
> +
> +static int palmas_start_srp(struct phy_companion *comparator)
> +{
> +	struct palmas_usb *palmas_usb = comparator_to_palmas(comparator);
> +
> +	palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
> +		PALMAS_USB_VBUS_CTRL_SET,
PALMAS_USB_VBUS_CTRL_SET_VBUS_DISCHRG
> +		| PALMAS_USB_VBUS_CTRL_SET_VBUS_IADP_SINK);
> +	palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
> +		PALMAS_USB_VBUS_CTRL_SET,
> +		PALMAS_USB_VBUS_CTRL_SET_VBUS_CHRG_VSYS |
> +		PALMAS_USB_VBUS_CTRL_SET_VBUS_IADP_SINK);
> +
> +	mdelay(100);

Why not msleep()? It's long enough to consider sleep.
Is this in an atomic context? (if so, 100msec seems even more awful)

> +
> +	palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
> +		PALMAS_USB_VBUS_CTRL_CLR,
> +		PALMAS_USB_VBUS_CTRL_SET_VBUS_CHRG_VSYS |
> +		PALMAS_USB_VBUS_CTRL_SET_VBUS_CHRG_VSYS);
> +
> +	return 0;
> +}
> +
> +static void palmas_dt_to_pdata(struct device_node *node,
> +		struct palmas_usb_platform_data *pdata)
> +{
> +	pdata->no_control_vbus = of_property_read_bool(node,
> +					"ti,no_control_vbus");
> +	pdata->wakeup = of_property_read_bool(node, "ti,wakeup");
> +}
> +
> +static int palmas_usb_probe(struct platform_device *pdev)
> +{

[]

> +	/* init spinlock for workqueue */
> +	spin_lock_init(&palmas_usb->lock);

[]

> +	/* init spinlock for workqueue */
> +	spin_lock_init(&palmas_usb->lock);

Why this lock is initialized again?

> +
> +	INIT_WORK(&palmas_usb->set_vbus_work, palmas_set_vbus_work);
> +

[]

> +
> +module_platform_driver(palmas_usb_driver);
> +
> +MODULE_ALIAS("platform:palmas-usb");
> +MODULE_AUTHOR("Graeme Gregory <gg@...mlogic.co.uk>");

Is this intentional?

> +MODULE_DESCRIPTION("Palmas USB transceiver driver");
> +MODULE_LICENSE("GPL");
> +MODULE_DEVICE_TABLE(of, of_palmas_match_tbl);
>


Cheers,
MyungJoo


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