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

Roger Quadros
2018-03-20T11:02:33Z

On 20/03/18 12:55, Roger Quadros wrote:
> On 19/03/18 18:12, 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
>
> That is about wakeup-source and not about whether remote wakeup should be enabled or not.

correction. It indeed means enable/disable wakeup :).

> i.e. wakeup-source can be present but wakeup can still be disabled by the user via sysfs.
>
>>
>>>> - 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?
>
> Looks fine to me. However one thing is still not clear. How does the PHY driver
> decide if it needs to do a full power off or partial power off?
> It doesn't know about the roothub's device_may_wakeup() status.
>
>> 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);
>>>>>>
>>>>>
>>>
>

--
cheers,
-roger

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