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

Chunfeng Yun
2018-03-20T12:04:27Z

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.

> >> - 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