Re: [PATCH usb-next v10 3/8] usb: core: add a wrapper for the USB PHYs on the HCD

Roger Quadros
2018-03-21T11:30:43Z

Martin,

On 21/03/18 00:01, Martin Blumenstingl wrote:
> Hi Roger, Hi Chunfeng,
>
> On Tue, Mar 20, 2018 at 1:04 PM, Chunfeng Yun <chunfeng.yun-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org> wrote:
>> Hi Martin & Roger:
>>
>> On Mon, 2018-03-19 at 17:12 +0100, Martin Blumenstingl wrote:
>>> Hi Roger,
>>>
>>> On Mon, Mar 19, 2018 at 9:49 AM, Roger Quadros <rogerq-l0cyMroinI0@public.gmane.org> wrote:
>>>> Hi,
>>>>
>>>> On 19/03/18 00:29, Martin Blumenstingl wrote:
>>>>> Hi Roger,
>>>>>
>>>>> On Fri, Mar 16, 2018 at 3:32 PM, Roger Quadros <rogerq-l0cyMroinI0@public.gmane.org> wrote:
>>>>>> +some TI folks
>>>>>>
>>>>>> Hi Martin,
>>>>>>
>>>>>> On 18/02/18 20:44, Martin Blumenstingl wrote:
>>>>>>> Many SoC platforms have separate devices for the USB PHY which are
>>>>>>> registered through the generic PHY framework. These PHYs have to be
>>>>>>> enabled to make the USB controller actually work. They also have to be
>>>>>>> disabled again on shutdown/suspend.
>>>>>>>
>>>>>>> Currently (at least) the following HCI platform drivers are using custom
>>>>>>> code to obtain all PHYs via devicetree for the roothub/controller and
>>>>>>> disable/enable them when required:
>>>>>>> - ehci-platform.c has ehci_platform_power_{on,off}
>>>>>>> - xhci-mtk.c has xhci_mtk_phy_{init,exit,power_on,power_off}
>>>>>>> - ohci-platform.c has ohci_platform_power_{on,off}
>>>>>>>
>>>>>>> With this new wrapper the USB PHYs can be specified directly in the
>>>>>>> USB controller's devicetree node (just like on the drivers listed
>>>>>>> above). This allows SoCs like the Amlogic Meson GXL family to operate
>>>>>>> correctly once this is wired up correctly. These SoCs use a dwc3
>>>>>>> controller and require all USB PHYs to be initialized (if one of the USB
>>>>>>> PHYs it not initialized then none of USB port works at all).
>>>>>>>
>>>>>>> Signed-off-by: Martin Blumenstingl <martin.blumenstingl-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
>>>>>>> Tested-by: Yixun Lan <yixun.lan-LpR1jeaWuhtBDgjK7y7TUQ@public.gmane.org>
>>>>>>> Cc: Neil Armstrong <narmstrong-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
>>>>>>> Cc: Chunfeng Yun <chunfeng.yun-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
>>>>>>
>>>>>> This patch is breaking low power cases on TI SoCs when USB is in host mode.
>>>>>> I'll explain why below.
>>>>> based on your explanation and reading the TI PHY drivers I am assuming
>>>>> that the affected SoCs are using the "phy-omap-usb2" driver
>>>>>
>>>> yes and phy-ti-pipe3 as well i.e. "ti,phy-usb3" and "ti,omap-usb3"
>>> I missed that, thanks
>>>
>>>>>>> ---
>>>>>>> drivers/usb/core/Makefile | 2 +-
>>>>>>> drivers/usb/core/phy.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++
>>>>>>> drivers/usb/core/phy.h | 7 ++
>>>>>>> 3 files changed, 166 insertions(+), 1 deletion(-)
>>>>>>> create mode 100644 drivers/usb/core/phy.c
>>>>>>> create mode 100644 drivers/usb/core/phy.h
>>>>>>>
>>>>>>> diff --git a/drivers/usb/core/Makefile b/drivers/usb/core/Makefile
>>>>>>> index 92c9cefb4317..18e874b0441e 100644
>>>>>>> --- a/drivers/usb/core/Makefile
>>>>>>> +++ b/drivers/usb/core/Makefile
>>>>>>> @@ -6,7 +6,7 @@
>>>>>>> usbcore-y := usb.o hub.o hcd.o urb.o message.o driver.o
>>>>>>> usbcore-y += config.o file.o buffer.o sysfs.o endpoint.o
>>>>>>> usbcore-y += devio.o notify.o generic.o quirks.o devices.o
>>>>>>> -usbcore-y += port.o
>>>>>>> +usbcore-y += phy.o port.o
>>>>>>>
>>>>>>> usbcore-$(CONFIG_OF) += of.o
>>>>>>> usbcore-$(CONFIG_USB_PCI) += hcd-pci.o
>>>>>>> diff --git a/drivers/usb/core/phy.c b/drivers/usb/core/phy.c
>>>>>>> new file mode 100644
>>>>>>> index 000000000000..09b7c43c0ea4
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/usb/core/phy.c
>>>>>>> @@ -0,0 +1,158 @@
>>>>>>> +// SPDX-License-Identifier: GPL-2.0+
>>>>>>> +/*
>>>>>>> + * A wrapper for multiple PHYs which passes all phy_* function calls to
>>>>>>> + * multiple (actual) PHY devices. This is comes handy when initializing
>>>>>>> + * all PHYs on a HCD and to keep them all in the same state.
>>>>>>> + *
>>>>>>> + * Copyright (C) 2018 Martin Blumenstingl <martin.blumenstingl-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
>>>>>>> + */
>>>>>>> +
>>>>>>> +#include <linux/device.h>
>>>>>>> +#include <linux/list.h>
>>>>>>> +#include <linux/phy/phy.h>
>>>>>>> +#include <linux/of.h>
>>>>>>> +
>>>>>>> +#include "phy.h"
>>>>>>> +
>>>>>>> +struct usb_phy_roothub {
>>>>>>> + struct phy *phy;
>>>>>>> + struct list_head list;
>>>>>>> +};
>>>>>>> +
>>>>>>> +static struct usb_phy_roothub *usb_phy_roothub_alloc(struct device *dev)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> +
>>>>>>> + roothub_entry = devm_kzalloc(dev, sizeof(*roothub_entry), GFP_KERNEL);
>>>>>>> + if (!roothub_entry)
>>>>>>> + return ERR_PTR(-ENOMEM);
>>>>>>> +
>>>>>>> + INIT_LIST_HEAD(&roothub_entry->list);
>>>>>>> +
>>>>>>> + return roothub_entry;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int usb_phy_roothub_add_phy(struct device *dev, int index,
>>>>>>> + struct list_head *list)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> + struct phy *phy = devm_of_phy_get_by_index(dev, dev->of_node, index);
>>>>>>> +
>>>>>>> + if (IS_ERR_OR_NULL(phy)) {
>>>>>>> + if (!phy || PTR_ERR(phy) == -ENODEV)
>>>>>>> + return 0;
>>>>>>> + else
>>>>>>> + return PTR_ERR(phy);
>>>>>>> + }
>>>>>>> +
>>>>>>> + roothub_entry = usb_phy_roothub_alloc(dev);
>>>>>>> + if (IS_ERR(roothub_entry))
>>>>>>> + return PTR_ERR(roothub_entry);
>>>>>>> +
>>>>>>> + roothub_entry->phy = phy;
>>>>>>> +
>>>>>>> + list_add_tail(&roothub_entry->list, list);
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +struct usb_phy_roothub *usb_phy_roothub_init(struct device *dev)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *phy_roothub;
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> + struct list_head *head;
>>>>>>> + int i, num_phys, err;
>>>>>>> +
>>>>>>> + num_phys = of_count_phandle_with_args(dev->of_node, "phys",
>>>>>>> + "#phy-cells");
>>>>>>> + if (num_phys <= 0)
>>>>>>> + return NULL;
>>>>>>> +
>>>>>>> + phy_roothub = usb_phy_roothub_alloc(dev);
>>>>>>> + if (IS_ERR(phy_roothub))
>>>>>>> + return phy_roothub;
>>>>>>> +
>>>>>>> + for (i = 0; i < num_phys; i++) {
>>>>>>> + err = usb_phy_roothub_add_phy(dev, i, &phy_roothub->list);
>>>>>>> + if (err)
>>>>>>> + goto err_out;
>>>>>>> + }
>>>>>>> +
>>>>>>> + head = &phy_roothub->list;
>>>>>>> +
>>>>>>> + list_for_each_entry(roothub_entry, head, list) {
>>>>>>> + err = phy_init(roothub_entry->phy);
>>>>>>
>>>>>> The phy_init() function actually enables the PHY clocks.
>>>>>> It should be moved to the usb_phy_roothub_exit() routine just before calling phy_power_on().
>>>>> do you mean that phy_init should be moved to usb_phy_roothub_power_on
>>>>> (just before phy_power_on is called within usb_phy_roothub_power_on)?
>>>>>
>>>>
>>>> Yes.
>>>>
>>>>> an earlier version of my patch did exactly this, but it caused
>>>>> problems during a suspend/resume cycle on Mediatek devices
>>>>> Chunfeng Yun reported that issue here [0], quote from that mail for
>>>>> easier reading:
>>>>> "In order to keep link state on mt8173, we just power off all phys(not
>>>>> exit) when system enter suspend, then power on them again (needn't
>>>>> init, otherwise device will be disconnected) when system resume, this
>>>>> can avoid re-enumerating device."
>>>>>
>>>>>>> + if (err)
>>>>>>> + goto err_exit_phys;
>>>>>>> + }
>>>>>>> +
>>>>>>> + return phy_roothub;
>>>>>>> +
>>>>>>> +err_exit_phys:
>>>>>>> + list_for_each_entry_continue_reverse(roothub_entry, head, list)
>>>>>>> + phy_exit(roothub_entry->phy);
>>>>>>> +
>>>>>>> +err_out:
>>>>>>> + return ERR_PTR(err);
>>>>>>> +}
>>>>>>> +EXPORT_SYMBOL_GPL(usb_phy_roothub_init);
>>>>>>> +
>>>>>>> +int usb_phy_roothub_exit(struct usb_phy_roothub *phy_roothub)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> + struct list_head *head;
>>>>>>> + int err, ret = 0;
>>>>>>> +
>>>>>>> + if (!phy_roothub)
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> + head = &phy_roothub->list;
>>>>>>> +
>>>>>>> + list_for_each_entry(roothub_entry, head, list) {
>>>>>>> + err = phy_exit(roothub_entry->phy);
>>>>>>> + if (err)
>>>>>>> + ret = ret;
>>>>>>> + }
>>>>>>
>>>>>> phy_exit() should be moved to usb_phy_roothub_poweroff() just after calling phy_power_off().
>>>>> if I understood Chunfeng Yun correctly this will require
>>>>> re-enumeration of the USB devices after a suspend/resume cycle on
>>>>> Mediatek SoCs
>>>>>
>>>>
>>>> OK. I suppose that there are 2 cases
>>>> 1) Mediatek's case: USB controller context retained across suspend/resume.
>>>> Remote wakeup probably required.
>>>> No re-enumeration preferred after resume. phy_exit()/phy_init() must not be called
>>>> during suspend/resume to keep PHY link active.
>>> Documentation/devicetree/bindings/usb/mediatek,mtu3.txt indeed shows
>>> that the parent of the USB controller can be marked as "wakeup-source"
>>>
>>>> 2) TI's case: low power important: USB context is lost, OK to re-enumerate.
>>>> phy_exit()/phy_init() must be called during suspend/resume.
>>> ACK
>>>
>>>>>> With that there is nothing else being done here. Shouldn't we be doing the equivalent of
>>>>>> usb_phy_roothub_del_phy() and usb_phy_roothub_free() here?
>>>>>>
>>>>>>> +
>>>>>>> + return ret;
>>>>>>> +}
>>>>>>> +EXPORT_SYMBOL_GPL(usb_phy_roothub_exit);
>>>>>>> +
>>>>>>> +int usb_phy_roothub_power_on(struct usb_phy_roothub *phy_roothub)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> + struct list_head *head;
>>>>>>> + int err;
>>>>>>> +
>>>>>>> + if (!phy_roothub)
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> + head = &phy_roothub->list;
>>>>>>> +
>>>>>>> + list_for_each_entry(roothub_entry, head, list) {
>>>>>>> + err = phy_power_on(roothub_entry->phy);
>>>>>>> + if (err)
>>>>>>> + goto err_out;
>>>>>>> + }
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> +err_out:
>>>>>>> + list_for_each_entry_continue_reverse(roothub_entry, head, list)
>>>>>>> + phy_power_off(roothub_entry->phy);
>>>>>>> +
>>>>>>> + return err;
>>>>>>> +}
>>>>>>> +EXPORT_SYMBOL_GPL(usb_phy_roothub_power_on);
>>>>>>> +
>>>>>>> +void usb_phy_roothub_power_off(struct usb_phy_roothub *phy_roothub)
>>>>>>> +{
>>>>>>> + struct usb_phy_roothub *roothub_entry;
>>>>>>> +
>>>>>>> + if (!phy_roothub)
>>>>>>> + return;
>>>>>>> +
>>>>>>> + list_for_each_entry_reverse(roothub_entry, &phy_roothub->list, list)
>>>>>>> + phy_power_off(roothub_entry->phy);
>>>>>>
>>>>>> Not doing the phy_exit() here leaves the clocks enabled on our SoC and
>>>>>> we're no longer able to reach low power states on system suspend.
>>>>> I'm not sure where this problem should be solved:
>>>>> - set skip_phy_initialization in struct usb_hcd to 1 for the affected
>>>>> TI platforms
>>>>
>>>> Many TI platforms are affected, omap5*, dra7*, am43*
>>>>
>>>>> - fix this in the usb_phy_roothub code
>>>>
>>>> I'd vote for fixing it in the usb_phy_roothub code. How?
>>>> How about using the device_can_wakeup() to decide if we should call phy_exit()/init() or not?
>>>> If the USB device can't wakeup the system there is no point in keeping it powered/clocked right?
>>> @Chunfeng: can you confirm Roger's idea that we could call phy_exit if
>>> the controller is *NOT* marked as "wakeup-source"?
>>> I am also not sure if it would work, since the "wakeup-source"
>>> property is defined on the USB controller's parent node in case of the
>>> Mediatek MTU3 (Mediatek USB3.0 DRD) controller
>>>
>> Very sorry, I forgot that MTU3 & xHCI drivers always set them as wakeup
>> devices by device_init_wakeup(dev, true),but not dependent on
>> "wakeup-source" property, so maybe we can use device_can_wakeup() to
>> decide whether call phy_exit()/init() or not.
> the 64-bit Amlogic Meson GXL/GXM SoCs don't support suspend/resume
> yet, so I cannot test this
> based on this suggestion I threw up two patches which are *compile
> tested only* based on Greg's usb-next branch
> you can find them here: [0] (as well as attached to this mail)
>
> @Chunfeng: can you please test this on one of your Mediatek SoCs?
> @Roger: can you please test this on a TI SoC?
>
> (apologies in advance if these patches don't work)
>
> please note that I won't have access to my computer until Saturday.
> if these patches need to be rewritten/replaced/etc. then feel free to
> send your own version to the list

Had to do the following to build

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 6d4a419..2884607 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2262,7 +2262,7 @@ int hcd_bus_suspend(struct usb_device *rhdev, pm_message_t msg)
hcd->state = HC_STATE_SUSPENDED;

if (!PMSG_IS_AUTO(msg))
- usb_phy_roothub_suspend(hcd->phy_roothub);
+ usb_phy_roothub_suspend(&rhdev->dev, hcd->phy_roothub);

/* Did we race with a root-hub wakeup event? */
if (rhdev->do_remote_wakeup) {
@@ -2302,7 +2302,7 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
}

if (!PMSG_IS_AUTO(msg)) {
- status = usb_phy_roothub_resume(hcd->phy_roothub);
+ status = usb_phy_roothub_resume(&rhdev->dev, hcd->phy_roothub);
if (status)
return status;
}
@@ -2344,7 +2344,7 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
}
} else {
hcd->state = old_state;
- usb_phy_roothub_suspend(hcd->phy_roothub);
+ usb_phy_roothub_suspend(&rhdev->dev, hcd->phy_roothub);
dev_dbg(&rhdev->dev, "bus %s fail, err %d\n",
"resume", status);
if (status != -ESHUTDOWN)

And the following to fix runtime issues

diff --git a/drivers/usb/core/phy.c b/drivers/usb/core/phy.c
index 2eca371..8598906 100644
--- a/drivers/usb/core/phy.c
+++ b/drivers/usb/core/phy.c
@@ -32,9 +32,9 @@ static int usb_phy_roothub_add_phy(struct device *dev, int index,
return PTR_ERR(phy);
}

- roothub_entry = usb_phy_roothub_alloc(dev);
- if (IS_ERR(roothub_entry))
- return PTR_ERR(roothub_entry);
+ roothub_entry = devm_kzalloc(dev, sizeof(*roothub_entry), GFP_KERNEL);
+ if (!roothub_entry)
+ return -ENOMEM;

roothub_entry->phy = phy;

@@ -162,7 +162,7 @@ int usb_phy_roothub_suspend(struct device *dev,
usb_phy_roothub_power_off(phy_roothub);

/* keep the PHYs initialized so the device can wake up the system */
- if (device_can_wakeup(dev))
+ if (device_may_wakeup(dev))
return 0;

return usb_phy_roothub_exit(phy_roothub);

Here are my obervations
- if wakeup is disabled it works fine as expected, phy_exit() is called and I'm able to reach
low power states.

- if wakeup is enabled (/sys/bus/usb/device/usb2/power/wakeup), then hcd_bus_suspend() is never called
and so phy_power_off won't be called either.

This means that the device_may_wakeup() check is redundant. Sorry for suggesting this.

This also means that wakeup is not enabled on Chunfeng's platform. Chunfeng, can you confirm this?
What does /sys/bus/usb/device/usb<?>/power/wakeup say?

Chunfeng sent a patch [1] to set shared_hcd->skip_phy_initialization for the mtk platform.
Chunfeng, why did you need this patch?

[1] - https://patchwork.kernel.org/patch/10298641/

What options do we have now to fix the original issue?

Chungfeng, can you set skip_phy_initialization for the hcd that has PHY's linked to it?
Then usb_phy_roothub_*() driver will be a no-op for you. And we could revert to the original approach
of doing phy_power_off() as well as phy_exit() during suspend.

Alternatively, Martin, how about not relying on skip_phy_initialization flag but having default behaviour
of no-op for the usb_phy_roothub_*() driver. As platforms migrate to it they can set a new
flag in hcd to use it?

>
>>>>> - fix this in the PHY driver
>>>>
>>>> There is nothing to fix in the PHY driver. It is doing what it is supposed to do.
>>> I actually wonder if phy_ops should have explicit suspend/resume support:
>>> - assuming we define two new callbacks: .suspend and .resume
>>> - the PHY framework could call .power_off by default if .suspend is not defined
>>> - the PHY framework could call .power_on by default if .resume is not defined
>>> - drivers could set .suspend and .resume on their own, allowing more
>>> fine-grained control by for example *only* stopping the clock (but not
>>> re-initializing the registers, etc.)
>>>
>>> @Roger: what do you think about this?
>>> Kishon (the PHY framework maintainer) is also CC'ed - I would like to
>>> hear his opinion too
>>>
>>>>> - somewhere else
>>>>>
>>>>>>> +}
>>>>>>> +EXPORT_SYMBOL_GPL(usb_phy_roothub_power_off);
>>>>>>> diff --git a/drivers/usb/core/phy.h b/drivers/usb/core/phy.h
>>>>>>> new file mode 100644
>>>>>>> index 000000000000..6fde59bfbff8
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/usb/core/phy.h
>>>>>>> @@ -0,0 +1,7 @@
>>>>>>> +struct usb_phy_roothub;
>>>>>>> +
>>>>>>> +struct usb_phy_roothub *usb_phy_roothub_init(struct device *dev);
>>>>>>> +int usb_phy_roothub_exit(struct usb_phy_roothub *phy_roothub);
>>>>>>> +
>>>>>>> +int usb_phy_roothub_power_on(struct usb_phy_roothub *phy_roothub);
>>>>>>> +void usb_phy_roothub_power_off(struct usb_phy_roothub *phy_roothub);
>>>>>>>
>>>>>>
>>>>

>
> [0] https://github.com/xdarklight/linux/commits/usb-phy-roothub-suspend-rfc-v1
>

--
cheers,
-roger

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