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

Chunfeng Yun
2018-03-20T23:47:25Z

Hi Martin,

On Tue, 2018-03-20 at 22:57 +0100, Martin Blumenstingl wrote:
> Hello Kishon,
>
> On Tue, Mar 20, 2018 at 12:27 PM, Kishon Vijay Abraham I <kishon@ti.com> wrote:
> > Hi,
> >
> > On Monday 19 March 2018 09:42 PM, Martin Blumenstingl wrote:
> >> Hi Roger,
> >>
> >> On Mon, Mar 19, 2018 at 9:49 AM, Roger Quadros <rogerq@ti.com> 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@ti.com> 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@googlemail.com>
> >>>>>> Tested-by: Yixun Lan <yixun.lan@amlogic.com>
> >>>>>> Cc: Neil Armstrong <narmstrong@baylibre.com>
> >>>>>> Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
> >>>>>
> >>>>> 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@googlemail.com>
> >>>>>> + */
> >>>>>> +
> >>>>>> +#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:
> >
> > Not in favor of adding explicit suspend/resume ops since PM framework already
> > has those. I think we should let PHY drivers manage suspend/resume on its own
> > (after creating the dependency between the controller device and PHY using
> > device_link_add).
> even better if we can re-use some existing code!
>
> the platform I am working on (64-bit Amlogic Meson GXL/GXM) does not
> support suspend/resume yet, so unfortunately I cannot test this.
> besides that I have zero experience with suspend/resume logic.
>
> I'll try to read more about that topic, but I definitely need someone
> who could help testing if I have a patch ready
> in any case: I think implementing this should not be done for v4.17
> anymore - maybe we can find a small solution for v4.17 and switch to
> your proposed solution later (assuming nobody has arguments against
> that)
>
I'll test it.

Thanks
>
> Regards
> Martin