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

Martin Blumenstingl
2018-03-19T16:12:06Z

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

>> - 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);
>>>>
>>>
>
> <snip>
>
> --
> cheers,
> -roger
>
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Regards
Martin