Message-ID: <BYAPR07MB470991EB0AE200B6481AEE35DDD70@BYAPR07MB4709.namprd07.prod.outlook.com>
Date:   Mon, 26 Nov 2018 07:23:11 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Roger Quadros <rogerq@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alan Douglas <adouglas@...ence.com>,
        "jbergsagel@...com" <jbergsagel@...com>,
        "nsekhar@...com" <nsekhar@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        "peter.chen@....com" <peter.chen@....com>,
        Pawel Jez <pjez@...ence.com>, Rahul Kumar <kurahul@...ence.com>
Subject: RE: [RFC PATCH v2 05/15] usb:cdns3: Added DRD support

Hi Roger,

>On 18/11/18 12:09, Pawel Laszczak wrote:
>> Patch adds supports for detecting Host/Device mode.
>> Controller has additional OTG register that allow
>> implement even whole OTG functionality.
>> At this moment patch adds support only for detecting
>> the appropriate mode based on strap pins and ID pin.
>>
>> Signed-off-by: Pawel Laszczak <pawell@...ence.com>
>> ---
>>  drivers/usb/cdns3/Makefile |   2 +-
>>  drivers/usb/cdns3/core.c   |  27 +++--
>>  drivers/usb/cdns3/drd.c    | 229 +++++++++++++++++++++++++++++++++++++
>>  drivers/usb/cdns3/drd.h    | 122 ++++++++++++++++++++
>>  4 files changed, 372 insertions(+), 8 deletions(-)
>>  create mode 100644 drivers/usb/cdns3/drd.c
>>  create mode 100644 drivers/usb/cdns3/drd.h
>>
>> diff --git a/drivers/usb/cdns3/Makefile b/drivers/usb/cdns3/Makefile
>> index 02d25b23c5d3..e779b2a2f8eb 100644
>> --- a/drivers/usb/cdns3/Makefile
>> +++ b/drivers/usb/cdns3/Makefile
>> @@ -1,5 +1,5 @@
>>  obj-$(CONFIG_USB_CDNS3)			+= cdns3.o
>>  obj-$(CONFIG_USB_CDNS3_PCI_WRAP)	+= cdns3-pci.o
>>
>> -cdns3-y					:= core.o
>> +cdns3-y					:= core.o drd.o
>>  cdns3-pci-y		 		:= cdns3-pci-wrap.o
>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>> index f9055d4da67f..dbee4325da7f 100644
>> --- a/drivers/usb/cdns3/core.c
>> +++ b/drivers/usb/cdns3/core.c
>> @@ -17,6 +17,7 @@
>>
>>  #include "gadget.h"
>>  #include "core.h"
>> +#include "drd.h"
>>
>>  static inline struct cdns3_role_driver *cdns3_get_current_role_driver(struct cdns3 *cdns)
>>  {
>> @@ -57,8 +58,10 @@ static inline void cdns3_role_stop(struct cdns3 *cdns)
>>  static enum cdns3_roles cdns3_get_role(struct cdns3 *cdns)
>>  {
>>  	if (cdns->roles[CDNS3_ROLE_HOST] && cdns->roles[CDNS3_ROLE_GADGET]) {
>> -		//TODO: implements selecting device/host mode
>> -		return CDNS3_ROLE_HOST;
>> +		if (cdns3_is_host(cdns))
>> +			return CDNS3_ROLE_HOST;
>> +		if (cdns3_is_device(cdns))
>> +			return CDNS3_ROLE_GADGET;
>>  	}
>>  	return cdns->roles[CDNS3_ROLE_HOST]
>>  		? CDNS3_ROLE_HOST
>> @@ -124,6 +127,12 @@ static irqreturn_t cdns3_irq(int irq, void *data)
>>  	struct cdns3 *cdns = data;
>>  	irqreturn_t ret = IRQ_NONE;
>>
>> +	if (cdns->dr_mode == USB_DR_MODE_OTG) {
>> +		ret = cdns3_drd_irq(cdns);
>> +		if (ret == IRQ_HANDLED)
>> +			return ret;
>> +	}
>
>The kernel's shared IRQ model takes care of sharing the same interrupt
>between different devices and their drivers. You don't need to manually
>handle it here. Just let all 3 drivers do a request_irq() and have
>handlers check if the IRQ was theirs or not and return IRQ_HANDLED or
>IRQ_NONE accordingly.
>
>Looks like you can do away with irq member of the role driver struct.

Ok, I will split it into 3 separate part, but in this case, I additionally have to check the current 
role in ISR function. Driver can't read host side registers when controller works in device role 
and vice versa. One part of controller is kept in reset. Only DRD registers are common and are all accessible.

>> +
>>  	/* Handle device/host interrupt */
>>  	if (cdns->role != CDNS3_ROLE_END)
>>  		ret = cdns3_get_current_role_driver(cdns)->irq(cdns);
>> @@ -176,11 +185,8 @@ static void cdns3_role_switch(struct work_struct *work)
>>
>>  	cdns = container_of(work, struct cdns3, role_switch_wq);
>>
>> -	//TODO: implements this functions.
>> -	//host = cdns3_is_host(cdns);
>> -	//device = cdns3_is_device(cdns);
>> -	host = 1;
>> -	device = 0;
>> +	host = cdns3_is_host(cdns);
>> +	device = cdns3_is_device(cdns);
>
>What if there is a ID transition between the 2 functions so that
>and both host and device become true?
>Since you are checking the ID level separately in both the functions.
>
>How about instead having cdns3_get_id() and using
>it to start/stop relevant roles if we are in OTG mode.
>
>Is this going to be used for a role switch even if we're not in OTG mode?
>If not then it is a BUG if we get here.
>
Good point.
User can change current mode by debugfs and then this function will also invoked.
Probably I use  cdns3_get_id as you suggest. 

>>
>>  	if (host)
>>  		role = CDNS3_ROLE_HOST;
>> @@ -194,6 +200,12 @@ static void cdns3_role_switch(struct work_struct *work)
>>  	pm_runtime_get_sync(cdns->dev);
>>  	cdns3_role_stop(cdns);
>>
>> +	if (cdns->desired_dr_mode != cdns->current_dr_mode) {
>
>This is about roles, why are we checking dr_mode here?

Because after changing dr_mode by means of debugfs we need to update mode. 
Driver should do this after stopping the previous role.  I will move this condition 
to cdns3_drd_update_mode and add comment in this place. 

>
>> +		cdns3_drd_update_mode(cdns);
>> +		host = cdns3_is_host(cdns);
>> +		device = cdns3_is_device(cdns);
>> +	}
>> +
>>  	if (host) {
>>  		if (cdns->roles[CDNS3_ROLE_HOST])
>>  			cdns3_do_role_switch(cdns, CDNS3_ROLE_HOST);
>> @@ -287,6 +299,7 @@ static int cdns3_probe(struct platform_device *pdev)
>>  	if (ret)
>>  		goto err2;
>>
>> +	ret = cdns3_drd_init(cdns);
>>  	if (ret)
>>  		goto err2;
>>
>> diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
>> new file mode 100644
>> index 000000000000..ac741c80e776
>> --- /dev/null
>> +++ b/drivers/usb/cdns3/drd.c
>> @@ -0,0 +1,229 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Cadence USBSS DRD Driver.
>> + *
>> + * Copyright (C) 2018 Cadence.
>> + *
>> + * Author: Pawel Laszczak <pawell@...ence.com
>> + *
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/delay.h>
>> +#include <linux/usb/otg.h>
>> +
>> +#include "gadget.h"
>> +#include "drd.h"
>> +
>> +/**
>> + * cdns3_set_mode - change mode of OTG Core
>> + * @cdns: pointer to context structure
>> + * @mode: selected mode from cdns_role
>> + */
>> +void cdns3_set_mode(struct cdns3 *cdns, enum usb_dr_mode mode)
>> +{
>> +	u32 reg;
>> +
>> +	cdns->current_dr_mode = mode;
>> +	switch (mode) {
>> +	case USB_DR_MODE_PERIPHERAL:
>> +		dev_info(cdns->dev, "Set controller to Gadget mode\n");
>> +		writel(OTGCMD_DEV_BUS_REQ | OTGCMD_OTG_DIS,
>> +		       &cdns->otg_regs->cmd);
>> +		break;
>> +	case USB_DR_MODE_HOST:
>> +		dev_info(cdns->dev, "Set controller to Host mode\n");
>> +		writel(OTGCMD_HOST_BUS_REQ | OTGCMD_OTG_DIS,
>> +		       &cdns->otg_regs->cmd);
>> +		break;
>> +	case USB_DR_MODE_OTG:
>> +		dev_info(cdns->dev, "Set controller to OTG mode\n");
>> +		reg = readl(&cdns->otg_regs->ctrl1);
>> +		reg |= OTGCTRL1_IDPULLUP;
>> +		writel(reg, &cdns->otg_regs->ctrl1);
>> +
>> +		/* wait until valid ID (ID_VALUE) can be sampled (50ms). */
>> +		mdelay(50);
>> +		break;
>> +	default:
>> +		cdns->current_dr_mode = USB_DR_MODE_UNKNOWN;
>> +		dev_err(cdns->dev, "Unsupported mode of operation %d\n", mode);
>> +		return;
>> +	}
>> +}
>> +
>> +static int cdns3_otg_get_id(struct cdns3 *cdns)
>> +{
>> +	int id;
>> +
>> +	id = readl(&cdns->otg_regs->sts) & OTGSTS_ID_VALUE;
>> +	dev_dbg(cdns->dev, "OTG ID: %d", id);
>> +	return id;
>> +}
>> +
>> +int cdns3_is_host(struct cdns3 *cdns)
>> +{
>> +	if (cdns->current_dr_mode == USB_DR_MODE_HOST)
>> +		return 1;
>
>Why do you need this?

I assumed that some SoC could have cut DRD /OTG and Device or Host part. 
In such case the driver cannot be based on ID pin. 
For only HOST it's not a problem because 
the standard XHCI driver will be used.  Probably I will remove this fragment.
>
>> +	else if (cdns->current_dr_mode == USB_DR_MODE_OTG)
>> +		if (!cdns3_otg_get_id(cdns))
>> +			return 1;
>> +
>> +	return 0;
>> +}
>> +
>> +int cdns3_is_device(struct cdns3 *cdns)
>> +{
>> +	if (cdns->current_dr_mode == USB_DR_MODE_PERIPHERAL)
>> +		return 1;
>> +	else if (cdns->current_dr_mode == USB_DR_MODE_OTG)
>> +		if (cdns3_otg_get_id(cdns))
>> +			return 1;
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * cdns3_otg_disable_irq - Disable all OTG interrupts
>> + * @cdns: Pointer to controller context structure
>> + */
>> +static void cdns3_otg_disable_irq(struct cdns3 *cdns)
>> +{
>> +	writel(0, &cdns->otg_regs->ien);
>> +}
>> +
>> +/**
>> + * cdns3_otg_enable_irq - enable id and sess_valid interrupts
>> + * @cdns: Pointer to controller context structure
>> + */
>> +static void cdns3_otg_enable_irq(struct cdns3 *cdns)
>> +{
>> +	writel(OTGIEN_ID_CHANGE_INT | OTGIEN_VBUSVALID_RISE_INT |
>> +	       OTGIEN_VBUSVALID_FALL_INT, &cdns->otg_regs->ien);
>> +}
>> +
>> +/**
>> + * cdns3_init_otg_mode - initialize drd controller
>> + * @cdns: Pointer to controller context structure
>> + *
>> + * Returns 0 on success otherwise negative errno
>> + */
>> +static void cdns3_init_otg_mode(struct cdns3 *cdns)
>> +{
>> +	cdns3_otg_disable_irq(cdns);
>> +	/* clear all interrupts */
>> +	writel(~0, &cdns->otg_regs->ivect);
>> +
>> +	cdns3_set_mode(cdns, USB_DR_MODE_OTG);
>> +
>> +	cdns3_otg_enable_irq(cdns);
>> +}
>> +
>> +/**
>> + * cdns3_drd_update_mode - initialize mode of operation
>
>Looks like this will be called only once. How about calling it
>
>cdns3_drd_init_mode()?

It will be also called after changing dr_mode from debugfs.

>> + * @cdns: Pointer to controller context structure
>> + *
>> + * Returns 0 on success otherwise negative errno
>> + */
>> +int cdns3_drd_update_mode(struct cdns3 *cdns)
>> +{
>> +	int ret = 0;
>> +
>> +	switch (cdns->desired_dr_mode) {
>
>I think we can get rid of desired_dr_mode member in struct cdns.
>Just pass the mode as an argument to cdns3_drd_init_mode()

This will be used also in patch that introduce debugfs. This filed is also used 
during changing dr_mode from user space.

My intention was:
dr_mode - indicated what driver can support, this filed based on dr_mode from device tree, 
	     straps bits from otg register and kernel configuration. 
desired_ dr_mode - the next mode desired by user, changed by debugfs 
current_dr_mode  - actually selected mode 

>
>And we already have cdns->dr_mode.
>
>> +	case USB_DR_MODE_PERIPHERAL:
>> +		cdns3_set_mode(cdns, USB_DR_MODE_PERIPHERAL);
>> +		break;
>> +	case USB_DR_MODE_HOST:
>> +		cdns3_set_mode(cdns, USB_DR_MODE_HOST);
>> +		break;
>> +	case USB_DR_MODE_OTG:
>> +		cdns3_init_otg_mode(cdns);
>> +		break;
>> +	default:
>> +		dev_err(cdns->dev, "Unsupported mode of operation %d\n",
>> +			cdns->dr_mode);
>> +		return -EINVAL;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +irqreturn_t cdns3_drd_irq(struct cdns3 *cdns)
>> +{
>> +	irqreturn_t ret = IRQ_NONE;
>> +	u32 reg;
>> +
>> +	if (cdns->dr_mode != USB_DR_MODE_OTG)
>> +		return ret;
>> +
>> +	reg = readl(&cdns->otg_regs->ivect);
>> +	if (!reg)
>> +		return ret;
>> +
>> +	if (reg & OTGIEN_ID_CHANGE_INT) {
>> +		int id = cdns3_otg_get_id(cdns);
>> +
>> +		dev_dbg(cdns->dev, "OTG IRQ: new ID: %d\n",
>> +			cdns3_otg_get_id(cdns));
>> +
>> +		if (id)
>> +			cdns->role = CDNS3_ROLE_GADGET;
>> +		else
>> +			cdns->role = CDNS3_ROLE_HOST;
>
>Why check ID and set role here? It might change by the time
>the role_switch_wq starts up. Why not check the ID status there?
>
>Also directly changing role here doesn't make sense as
>there will be a mismatch between currently active role and cdns->role.

Yes this fragment does not make sense.  
>> +
>> +		queue_work(system_freezable_wq, &cdns->role_switch_wq);
>> +
>> +		ret = IRQ_HANDLED;
>> +	}
>> +
>> +	writel(~0, &cdns->otg_regs->ivect);
>> +	return IRQ_HANDLED;
>
>return ret;
>
>> +}
>> +
>> +int cdns3_drd_init(struct cdns3 *cdns)
>> +{
>> +	enum usb_dr_mode dr_mode;
>> +	int ret = 0;
>> +	u32 state;
>> +
>> +	state = OTGSTS_STRAP(readl(&cdns->otg_regs->sts));
>> +
>> +	dr_mode = cdns->dr_mode;
>> +	if (state == OTGSTS_STRAP_HOST) {
>> +		dev_info(cdns->dev, "Controller strapped to HOST\n");
>> +		dr_mode = USB_DR_MODE_HOST;
>> +		if (cdns->dr_mode != USB_DR_MODE_HOST &&
>> +		    cdns->dr_mode != USB_DR_MODE_OTG)
>> +			ret = -EINVAL;
>> +	} else if (state == OTGSTS_STRAP_GADGET) {
>> +		dev_info(cdns->dev, "Controller strapped to PERIPHERAL\n");
>> +		dr_mode = USB_DR_MODE_PERIPHERAL;
>> +		if (cdns->dr_mode != USB_DR_MODE_PERIPHERAL &&
>> +		    cdns->dr_mode != USB_DR_MODE_OTG)
>> +			ret = -EINVAL;
>> +	}
>> +
>> +	if (ret) {
>> +		dev_err(cdns->dev, "Incorrect DRD configuration\n");
>> +		return ret;
>> +	}
>> +
>> +	//Updating DR mode according to strap.
>> +	cdns->dr_mode = dr_mode;
>> +	cdns->desired_dr_mode = dr_mode;
>> +	cdns->current_dr_mode = USB_DR_MODE_UNKNOWN;
>> +
>> +	dev_info(cdns->dev, "Controller Device ID: %08lx, Revision ID: %08lx\n",
>> +		 CDNS_RID(readl(&cdns->otg_regs->rid)),
>> +		 CDNS_DID(readl(&cdns->otg_regs->did)));
>
>dev_info should be moved at the end if cdns3_drd_update_mode() if it succeeded.
Ok, 
>
>> +
>> +	state = readl(&cdns->otg_regs->sts);
>> +	if (OTGSTS_OTG_NRDY(state) != 0) {
>> +		dev_err(cdns->dev, "Cadence USB3 OTG device not ready\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	ret = cdns3_drd_update_mode(cdns);
>> +
>> +	return ret;
>> +}
>> diff --git a/drivers/usb/cdns3/drd.h b/drivers/usb/cdns3/drd.h
>> new file mode 100644
>> index 000000000000..0faa7520ecac
>> --- /dev/null
>> +++ b/drivers/usb/cdns3/drd.h
>> @@ -0,0 +1,122 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Cadence USB3 DRD part of USBSS driver
>> + *
>> + * Copyright (C) 2018 Cadence.
>> + *
>> + * Author: Pawel Laszczak <pawell@...ence.com>
>> + */
>> +#ifndef __LINUX_CDNS3_DRD
>> +#define __LINUX_CDNS3_DRD
>> +
>> +#include <linux/usb/otg.h>
>> +#include <linux/phy/phy.h>
>> +#include "core.h"
>> +
>> +/*  DRD register interface. */
>> +struct cdns3_otg_regs {
>> +	__le32 did;
>> +	__le32 rid;
>> +	__le32 capabilities;
>> +	__le32 reserved1;
>> +	__le32 cmd;
>> +	__le32 sts;
>> +	__le32 state;
>> +	__le32 reserved2;
>> +	__le32 ien;
>> +	__le32 ivect;
>> +	__le32 refclk;
>> +	__le32 tmr;
>> +	__le32 reserved3[4];
>> +	__le32 simulate;
>> +	__le32 override;
>> +	__le32 susp_ctrl;
>> +	__le32 reserved4;
>> +	__le32 anasts;
>> +	__le32 adp_ramp_time;
>> +	__le32 ctrl1;
>> +	__le32 ctrl2;
>> +};
>> +
>> +/* CDNS_RID - bitmasks */
>> +#define CDNS_RID(p)			((p) & GENMASK(15, 0))
>> +
>> +/* CDNS_VID - bitmasks */
>> +#define CDNS_DID(p)			((p) & GENMASK(31, 0))
>> +
>> +/* OTGCMD - bitmasks */
>> +/* "Request the bus for Device mode. */
>> +#define OTGCMD_DEV_BUS_REQ	BIT(0)
>> +/* Request the bus for Host mode */
>> +#define OTGCMD_HOST_BUS_REQ		BIT(1)
>> +/* Enable OTG mode. */
>> +#define OTGCMD_OTG_EN			BIT(2)
>> +/* Disable OTG mode */
>> +#define OTGCMD_OTG_DIS			BIT(3)
>> +/*"Configure OTG as A-Device. */
>> +#define OTGCMD_A_DEV_EN			BIT(4)
>> +/*"Configure OTG as A-Device. */
>> +#define OTGCMD_A_DEV_DIS		BIT(5)
>> +/* Drop the bus for Device mod	e. */
>> +#define OTGCMD_DEV_BUS_DROP		BIT(8)
>> +/* Drop the bus for Host mode*/
>> +#define OTGCMD_HOST_BUS_DROP		BIT(9)
>> +/* Power Down USBSS-DEV. */
>> +#define OTGCMD_DEV_POWER_OFF		BIT(11)
>> +/* Power Down CDNSXHCI. */
>> +#define OTGCMD_HOST_POWER_OFF		BIT(12)
>> +
>> +/* OTGIEN - bitmasks */
>> +/* ID change interrupt enable */
>> +#define OTGIEN_ID_CHANGE_INT		BIT(0)
>> +/* Vbusvalid fall detected interrupt enable.*/
>> +#define OTGIEN_VBUSVALID_RISE_INT	BIT(4)
>> +/* Vbusvalid fall detected interrupt enable */
>> +#define OTGIEN_VBUSVALID_FALL_INT	BIT(5)
>> +
>> +/* OTGSTS - bitmasks */
>> +/*
>> + * Current value of the ID pin. It is only valid when idpullup in
>> + *  OTGCTRL1_TYPE register is set to '1'.
>> + */
>> +#define OTGSTS_ID_VALUE			BIT(0)
>> +/* Current value of the vbus_valid */
>> +#define OTGSTS_VBUS_VALID		BIT(1)
>> +/* Current value of the b_sess_vld */
>> +#define OTGSTS_SESSION_VALID		BIT(2)
>> +/*Device mode is active*/
>> +#define OTGSTS_DEV_ACTIVE		BIT(3)
>> +/* Host mode is active. */
>> +#define OTGSTS_HOST_ACTIVE		BIT(4)
>> +/* OTG Controller not ready. */
>> +#define OTGSTS_OTG_NRDY_MASK		BIT(11)
>> +#define OTGSTS_OTG_NRDY(p)		((p) & OTGSTS_OTG_NRDY_MASK)
>> +/*
>> + * Value of the strap pins.
>> + * 000 - no default configuration
>> + * 010 - Controller initiall configured as Host
>> + * 100 - Controller initially configured as Device
>> + */
>> +#define OTGSTS_STRAP(p)			(((p) & GENMASK(14, 12)) >> 12)
>> +#define OTGSTS_STRAP_NO_DEFAULT_CFG	0x00
>> +#define OTGSTS_STRAP_HOST_OTG		0x01
>> +#define OTGSTS_STRAP_HOST		0x02
>> +#define OTGSTS_STRAP_GADGET		0x04
>> +/* Host mode is turned on. */
>> +#define OTGSTSE_XHCI_READYF		BIT(26)
>> +/* "Device mode is turned on .*/
>> +#define OTGSTS_DEV_READY		BIT(27)
>> +
>> +/* OTGREFCLK - bitmasks */
>> +#define OTGREFCLK_STB_CLK_SWITCH_EN	BIT(31)
>> +
>> +/* OTGCTRL1 - bitmasks */
>> +#define OTGCTRL1_IDPULLUP		BIT(24)
>> +
>> +int cdns3_is_host(struct cdns3 *cdns);
>> +int cdns3_is_device(struct cdns3 *cdns);
>> +int cdns3_drd_init(struct cdns3 *cdns);
>> +int cdns3_drd_update_mode(struct cdns3 *cdns);
>> +irqreturn_t cdns3_drd_irq(struct cdns3 *cdns);
>> +
>> +#endif /* __LINUX_CDNS3_DRD */
>>
>
>cheers,
>-roger
>--
>Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Thanks for all your comments.
Cheers 
Pawel

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