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

Roger Quadros
2018-03-19T08:49:55Z

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"

>>> ---
>>> 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.

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.

>> 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?

> - fix this in the PHY driver

There is nothing to fix in the PHY driver. It is doing what it is supposed to do.

> - 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

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