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Subject: Re: [PATCH v10 5/6] usb:cdns3 Add Cadence USB3 DRD Driver
To:     Pawel Laszczak <pawell@cadence.com>,
        "felipe.balbi@linux.intel.com" <felipe.balbi@linux.intel.com>
CC:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "jbergsagel@ti.com" <jbergsagel@ti.com>,
        "nsekhar@ti.com" <nsekhar@ti.com>, "nm@ti.com" <nm@ti.com>,
        Suresh Punnoose <sureshp@cadence.com>,
        Jayshri Dajiram Pawar <jpawar@cadence.com>,
        Rahul Kumar <kurahul@cadence.com>,
        Anil Joy Varughese <aniljoy@cadence.com>
References: <1563733939-21214-1-git-send-email-pawell@cadence.com>
 <1563733939-21214-6-git-send-email-pawell@cadence.com>
 <61a14c20-c02c-776c-6ce1-3dd5d6abac8e@ti.com>
 <BYAPR07MB47090324855158D2469C45FADDA80@BYAPR07MB4709.namprd07.prod.outlook.com>
From:   Roger Quadros <rogerq@ti.com>
Message-ID: <2a365912-a775-3b2a-6b9e-0bcb6971ccb2@ti.com>
Date:   Mon, 19 Aug 2019 13:59:37 +0300
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Pawel,

On 19/08/2019 13:30, Pawel Laszczak wrote:
> Hi,
> 
>>
>> On 21/07/2019 21:32, Pawel Laszczak wrote:
>>> This patch introduce new Cadence USBSS DRD driver to Linux kernel.
>>>
>>> The Cadence USBSS DRD Controller is a highly configurable IP Core which
>>> can be instantiated as Dual-Role Device (DRD), Peripheral Only and
>>> Host Only (XHCI)configurations.
>>>
>>> The current driver has been validated with FPGA platform. We have
>>> support for PCIe bus, which is used on FPGA prototyping.
>>>
>>> The host side of USBSS-DRD controller is compliant with XHCI
>>> specification, so it works with standard XHCI Linux driver.
>>>
>>> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
>>> ---
>>>  drivers/usb/Kconfig                |    2 +
>>>  drivers/usb/Makefile               |    2 +
>>>  drivers/usb/cdns3/Kconfig          |   46 +
>>>  drivers/usb/cdns3/Makefile         |   17 +
>>>  drivers/usb/cdns3/cdns3-pci-wrap.c |  203 +++
>>>  drivers/usb/cdns3/core.c           |  554 +++++++
>>>  drivers/usb/cdns3/core.h           |  109 ++
>>>  drivers/usb/cdns3/debug.h          |  171 ++
>>>  drivers/usb/cdns3/debugfs.c        |   87 ++
>>>  drivers/usb/cdns3/drd.c            |  390 +++++
>>>  drivers/usb/cdns3/drd.h            |  166 ++
>>>  drivers/usb/cdns3/ep0.c            |  914 +++++++++++
>>>  drivers/usb/cdns3/gadget-export.h  |   28 +
>>>  drivers/usb/cdns3/gadget.c         | 2338 ++++++++++++++++++++++++++++
>>>  drivers/usb/cdns3/gadget.h         | 1321 ++++++++++++++++
>>>  drivers/usb/cdns3/host-export.h    |   28 +
>>>  drivers/usb/cdns3/host.c           |   71 +
>>>  drivers/usb/cdns3/trace.c          |   11 +
>>>  drivers/usb/cdns3/trace.h          |  493 ++++++
>>>  19 files changed, 6951 insertions(+)
>>>  create mode 100644 drivers/usb/cdns3/Kconfig
>>>  create mode 100644 drivers/usb/cdns3/Makefile
>>>  create mode 100644 drivers/usb/cdns3/cdns3-pci-wrap.c
>>>  create mode 100644 drivers/usb/cdns3/core.c
>>>  create mode 100644 drivers/usb/cdns3/core.h
>>>  create mode 100644 drivers/usb/cdns3/debug.h
>>>  create mode 100644 drivers/usb/cdns3/debugfs.c
>>>  create mode 100644 drivers/usb/cdns3/drd.c
>>>  create mode 100644 drivers/usb/cdns3/drd.h
>>>  create mode 100644 drivers/usb/cdns3/ep0.c
>>>  create mode 100644 drivers/usb/cdns3/gadget-export.h
>>>  create mode 100644 drivers/usb/cdns3/gadget.c
>>>  create mode 100644 drivers/usb/cdns3/gadget.h
>>>  create mode 100644 drivers/usb/cdns3/host-export.h
>>>  create mode 100644 drivers/usb/cdns3/host.c
>>>  create mode 100644 drivers/usb/cdns3/trace.c
>>>  create mode 100644 drivers/usb/cdns3/trace.h
>>>
>>
>> <snip>
>>
>>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>>> new file mode 100644
>>> index 000000000000..900b2ce08162
>>> --- /dev/null
>>> +++ b/drivers/usb/cdns3/core.c
>>> @@ -0,0 +1,554 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Cadence USBSS DRD Driver.
>>> + *
>>> + * Copyright (C) 2018-2019 Cadence.
>>> + * Copyright (C) 2017-2018 NXP
>>> + * Copyright (C) 2019 Texas Instruments
>>> + *
>>> + * Author: Peter Chen <peter.chen@nxp.com>
>>> + *         Pawel Laszczak <pawell@cadence.com>
>>> + *         Roger Quadros <rogerq@ti.com>
>>> + */
>>> +
>>> +#include <linux/dma-mapping.h>
>>> +#include <linux/module.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/io.h>
>>> +#include <linux/pm_runtime.h>
>>> +
>>> +#include "gadget.h"
>>> +#include "core.h"
>>> +#include "host-export.h"
>>> +#include "gadget-export.h"
>>> +#include "drd.h"
>>> +#include "debug.h"
>>> +
>>> +static inline
>>> +struct cdns3_role_driver *cdns3_get_current_role_driver(struct cdns3 *cdns)
>>> +{
>>> +	WARN_ON(!cdns->roles[cdns->role]);
>>> +	return cdns->roles[cdns->role];
>>> +}
>>> +
>>> +static int cdns3_role_start(struct cdns3 *cdns, enum usb_role role)
>>> +{
>>> +	int ret;
>>> +
>>> +	if (WARN_ON(role > USB_ROLE_DEVICE))
>>> +		return 0;
>>> +
>>> +	mutex_lock(&cdns->mutex);
>>> +	cdns->role = role;
>>> +	mutex_unlock(&cdns->mutex);
>>> +
>>> +	if (role == USB_ROLE_NONE)
>>> +		return 0;
>>
>> We will need to have a role driver for NONE case so we can deal with
>> type-C cable swap case. I will post a patch at the end about this.
>> You can squash the patches and use them in the next revision.
> 
>>
>>> +
>>> +	if (!cdns->roles[role])
>>> +		return -ENXIO;
>>> +
>>> +	if (cdns->roles[role]->state == CDNS3_ROLE_STATE_ACTIVE)
>>> +		return 0;
>>> +
>>> +	mutex_lock(&cdns->mutex);
>>> +	if (role == USB_ROLE_HOST)
>>> +		cdns3_drd_switch_host(cdns, 1);
>>> +	else
>>> +		cdns3_drd_switch_gadget(cdns, 1);
>>
>> Please don't do this here. You can call them from the respective role
>> drivers at the start. i.e. __cdns3_host_init(), __cdns3_gadget_init()
> 
> Why it can't do this here?
> 
Because it looks so wrong. You are dealing with state specific functionality
in a generic role start/stop function.

When you add idle state then it doesn't scale well.

> Do we really want to mix  drd code with gadget/host ?

I don't see it like that. You are only doing host/gadget specific stuff
in the respective drivers right?
> 
>>> +
>>> +	ret = cdns->roles[role]->start(cdns);
>>> +	if (!ret)
>>> +		cdns->roles[role]->state = CDNS3_ROLE_STATE_ACTIVE;
>>> +	mutex_unlock(&cdns->mutex);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static void cdns3_role_stop(struct cdns3 *cdns)
>>> +{
>>> +	enum usb_role role = cdns->role;
>>> +
>>> +	if (WARN_ON(role > USB_ROLE_DEVICE))
>>> +		return;
>>> +
>>> +	if (role == USB_ROLE_NONE)
>>> +		return;
>>> +
>>> +	if (cdns->roles[role]->state == CDNS3_ROLE_STATE_INACTIVE)
>>> +		return;
>>> +
>>> +	mutex_lock(&cdns->mutex);
>>> +	cdns->roles[role]->stop(cdns);
>>> +	if (role == USB_ROLE_HOST)
>>> +		cdns3_drd_switch_host(cdns, 0);
>>> +	else
>>> +		cdns3_drd_switch_gadget(cdns, 0);
>>
>> No need to do this here. They can be done at the respective role
>> drivers at the end. i.e. cdns3_host_exit(), cdns3_gadget_exit()
>>
>>> +
>>> +	cdns->roles[role]->state = CDNS3_ROLE_STATE_INACTIVE;
>>> +	mutex_unlock(&cdns->mutex);
>>> +}
>>> +
>>> +static void cdns3_exit_roles(struct cdns3 *cdns)
>>> +{
>>> +	cdns3_role_stop(cdns);
>>> +	cdns3_drd_exit(cdns);
>>> +}
>>> +
>>> +enum usb_role cdsn3_real_role_switch_get(struct device *dev);
>>> +
>>> +/**
>>> + * cdns3_core_init_role - initialize role of operation
>>> + * @cdns: Pointer to cdns3 structure
>>> + *
>>> + * Returns 0 on success otherwise negative errno
>>> + */
>>> +static int cdns3_core_init_role(struct cdns3 *cdns)
>>> +{
>>> +	struct device *dev = cdns->dev;
>>> +	enum usb_dr_mode best_dr_mode;
>>> +	enum usb_dr_mode dr_mode;
>>> +	int ret = 0;
>>> +
>>> +	dr_mode = usb_get_dr_mode(dev);
>>> +	cdns->role = USB_ROLE_NONE;
>>> +
>>> +	/*
>>> +	 * If driver can't read mode by means of usb_get_dr_mode function then
>>> +	 * chooses mode according with Kernel configuration. This setting
>>> +	 * can be restricted later depending on strap pin configuration.
>>> +	 */
>>> +	if (dr_mode == USB_DR_MODE_UNKNOWN) {
>>> +		if (IS_ENABLED(CONFIG_USB_CDNS3_HOST) &&
>>> +		    IS_ENABLED(CONFIG_USB_CDNS3_GADGET))
>>> +			dr_mode = USB_DR_MODE_OTG;
>>> +		else if (IS_ENABLED(CONFIG_USB_CDNS3_HOST))
>>> +			dr_mode = USB_DR_MODE_HOST;
>>> +		else if (IS_ENABLED(CONFIG_USB_CDNS3_GADGET))
>>> +			dr_mode = USB_DR_MODE_PERIPHERAL;
>>> +	}
>>> +
>>> +	/*
>>> +	 * At this point cdns->dr_mode contains strap configuration.
>>> +	 * Driver try update this setting considering kernel configuration
>>> +	 */
>>> +	best_dr_mode = cdns->dr_mode;
>>> +
>>> +	if (dr_mode == USB_DR_MODE_OTG) {
>>> +		best_dr_mode = cdns->dr_mode;
>>> +	} else if (cdns->dr_mode == USB_DR_MODE_OTG) {
>>> +		best_dr_mode = dr_mode;
>>> +	} else if (cdns->dr_mode != dr_mode) {
>>> +		dev_err(dev, "Incorrect DRD configuration\n");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	dr_mode = best_dr_mode;
>>> +
>>> +	if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_HOST) {
>>> +		ret = cdns3_host_init(cdns);
>>> +		if (ret) {
>>> +			dev_err(dev, "Host initialization failed with %d\n",
>>> +				ret);
>>> +			goto err;
>>> +		}
>>> +	}
>>> +
>>> +	if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_PERIPHERAL) {
>>> +		ret = cdns3_gadget_init(cdns);
>>> +		if (ret) {
>>> +			dev_err(dev, "Device initialization failed with %d\n",
>>> +				ret);
>>> +			goto err;
>>> +		}
>>> +	}
>>> +
>>> +	cdns->desired_dr_mode = dr_mode;
>>> +	cdns->dr_mode = dr_mode;
>>> +
>>> +	/*
>>> +	 * desired_dr_mode might have changed so we need to update
>>> +	 * the controller configuration"?
>>> +	 */
>>> +	ret = cdns3_drd_update_mode(cdns);
>>> +	if (ret)
>>> +		goto err;
>>> +
>>> +	cdns->role = cdsn3_real_role_switch_get(cdns->dev);
>>> +
>>> +	ret = cdns3_role_start(cdns, cdns->role);
>>> +	if (ret) {
>>> +		dev_err(dev, "can't start %s role\n",
>>> +			cdns3_get_current_role_driver(cdns)->name);
>>> +		goto err;
>>> +	}
>>> +
>>> +	return ret;
>>> +err:
>>> +	cdns3_exit_roles(cdns);
>>> +	return ret;
>>> +}
>>> +
>>> +/**
>>> + * cdsn3_real_role_switch_get - get real role of controller based on hardware
>>> + *   settings.
>>> + * @dev: Pointer to device structure
>>> + *
>>> + * Returns role
>>> + */
>>> +enum usb_role cdsn3_real_role_switch_get(struct device *dev)
>>
>> let's not mix user space role_switch and HW based role swith.
>>
>> This function is really the HW based state machine. Let's rename it to
>>
>> * cdsn3_hw_role_state_machine - role switch state machine based on hw events
>> *
>> * @cdns: Pointer to controller structure
>> *
>> * Returns next role to be entered based on hw events.
>> */
>> static enum usb_role cdsn3_hw_role_state_machine(struct cdns3 *cdns)
>>
>>> +{
>>> +	struct cdns3 *cdns = dev_get_drvdata(dev);
>>> +	enum usb_role role;
>>> +	int id, vbus;
>>> +
>>> +	if (cdns->current_dr_mode != USB_DR_MODE_OTG)
>>> +		goto not_otg;
>>> +
>>> +	id = cdns3_get_id(cdns);
>>> +	vbus = cdns3_get_vbus(cdns);
>>> +
>>> +	/*
>>> +	 * Role change state machine
>>> +	 * Inputs: ID, VBUS
>>> +	 * Previous state: cdns->role
>>> +	 * Next state: role
>>> +	 */
>>> +	role = cdns->role;
>>> +
>>> +	switch (role) {
>>> +	case USB_ROLE_NONE:
>>> +		/*
>>> +		 * Driver treat USB_ROLE_NONE synonymous to IDLE state from
>>
>> s/treat/treats
>>
>>> +		 * controller specification.
>>> +		 */
>>> +		if (!id)
>>> +			role = USB_ROLE_HOST;
>>> +		else if (vbus)
>>> +			role = USB_ROLE_DEVICE;
>>> +		break;
>>> +	case USB_ROLE_HOST: /* from HOST, we can only change to NONE */
>>> +		if (id)
>>> +			role = USB_ROLE_NONE;
>>> +		break;
>>> +	case USB_ROLE_DEVICE: /* from GADGET, we can only change to NONE*/
>>> +		if (!vbus)
>>> +			role = USB_ROLE_NONE;
>>> +		break;
>>> +	}
>>> +
>>> +	dev_dbg(cdns->dev, "role %d -> %d\n", cdns->role, role);
>>> +
>>> +	return role;
>>> +
>>> +not_otg:
>>> +	if (cdns3_is_host(cdns))
>>> +		role = USB_ROLE_HOST;
>>> +	if (cdns3_is_device(cdns))
>>> +		role = USB_ROLE_DEVICE;
>>> +
>>> +	return role;
>>> +}
>>> +
>>> +/**
>>> + * cdns3_role_switch_set - work queue handler for role switch
>>> + *
>>> + * @dev: pointer to device object
>>> + * @role - the previous role
>>> + * Handles below events:
>>> + * - Role switch for dual-role devices
>>> + * - USB_ROLE_GADGET <--> USB_ROLE_NONE for peripheral-only devices
>>> + */
>>> +static int cdns3_role_switch_set(struct device *dev, enum usb_role role)
>>
>> Let's not use this for user space role switch but just for HW based switching
>> How about calling it
>>
>> int cdns3_hw_role_switch(struct cdns3 *cdns)
> 
> Ok, I will change name.
> 
>>
>>> +{
>>> +	struct cdns3 *cdns = dev_get_drvdata(dev);
>>> +	enum usb_role real_role = USB_ROLE_NONE;
>>> +	enum usb_role current_role;
>>
>> enum usb_role real_role, current_role;
>>
>>> +	int ret = 0;
>>> +
>>> +	/* Check if dr_mode was changed.*/
>>> +	ret = cdns3_drd_update_mode(cdns);
>>
> 
> After removing debugfs it's not longer needed. 
> 
>> Why is this check required? Who is going to change dr_mode?
>>
>>> +	if (ret)
>>> +		return ret;
>>
>> I think here we need to check if user overrides the role
>> using role switch sysfs. If yes then we ned ignore HW events
>> and just return here.
> 
> Should I add some extra flags for detecting this in CDNS3 driver 
> or we should assume that it will be added in role switch framework ?
> 

We can always add private flags.

>>
>>> +
>>> +	pm_runtime_get_sync(cdns->dev);
>>> +
>>> +	real_role = cdsn3_real_role_switch_get(cdns->dev);
>>
>>       current_role = cdns->role;
>>       real_role = cdsn3_hw_role_state_machine(cdns);
>>
>>> +
>>> +	/* Do nothing if nothing changed */
>>> +	if (cdns->role == real_role)
>>
>> 	if (current_role == real_role)
>>
>>> +		goto exit;
>>> +
>>> +	cdns3_role_stop(cdns);
>>> +
>>> +	real_role = cdsn3_real_role_switch_get(cdns->dev);
>>> +
>>> +	current_role = role;
>>
>> Remove above 2 lines. Don't need to get real role again
>> here as it will break the state machine.
>> If HW state changes, we will deal with it in next interrupt
>> not here.
>>
>>> +	dev_dbg(cdns->dev, "Switching role");
>>
>> 	dev_dbg(cdns->dev, "Switching role %d -> %d", current_role, real_role);
>>
>>> +
>>> +	ret = cdns3_role_start(cdns, real_role);
>>> +	if (ret) {
>>> +		/* Back to current role */
>>> +		dev_err(cdns->dev, "set %d has failed, back to %d\n",
>>> +			role, current_role);
>>
>> 			real_role, current_role
>>
>>> +		ret = cdns3_role_start(cdns, current_role);
>>> +		if (ret)
>>> +			dev_err(cdns->dev, "back to %d failed too\n",
>>> +				current_role);
>>> +	}
>>> +exit:
>>> +	pm_runtime_put_sync(cdns->dev);
>>> +	return ret;
>>> +}
>>
>> How about the below 2 functions for user space role switch handling.
>>
>> +/**
>> + * cdsn3_role_get - get current role of controller.
>> + *
>> + * @dev: Pointer to device structure
>> + *
>> + * Returns role
>> + */
>> +static enum usb_role cdns3_role_get(struct device *dev)
>> +{
>> +       struct cdns3 *cdns = dev_get_drvdata(dev);
>> +
>> +       return cdns->role;
>> +}
>> +
>> +/**
>> + * cdns3_role_set - set current role of controller.
>> + *
>> + * @dev: pointer to device object
>> + * @role - the previous role
>> + * Handles below events:
>> + * - Role switch for dual-role devices
>> + * - USB_ROLE_GADGET <--> USB_ROLE_NONE for peripheral-only devices
>> + */
>> +static int cdns3_role_set(struct device *dev, enum usb_role role)
>> +{
>> +       /* FIXME: doing nothing for now */
>>
>> Here we need to implement the user space switching logic.
>>
>> 1) If called change to desired role and set a userspace override flag
>> 2) How do we clear the userspace override flag so HW based switching can
>> continue? Need new API hook in struct usb_role_switch_desc?
>>
>> +       return -EPERM;
>> +}
>> +
> 
> But Felipe will complain for this empty function :).

I hope you will put something in there before sending v11 :).
Since you are getting rid of debugfs, you need to make this function work.
> 
>>> +
>>> +static const struct usb_role_switch_desc cdns3_switch_desc = {
>>> +	.set = cdns3_role_switch_set,
>>> +	.get = cdsn3_real_role_switch_get,
>>
>>       .set = cdns3_role_set,
>>       .get = cdns3_role_get,
>>
>>> +	.allow_userspace_control = true,
>>> +};
>>> +
>>
<snip>

cheers,
-roger
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