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 [off-list ref] wrote:

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Hi,

On Monday 19 March 2018 09:42 PM, Martin Blumenstingl wrote:

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Hi Roger,

On Mon, Mar 19, 2018 at 9:49 AM, Roger Quadros [off-list ref] wrote:

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Hi,

On 19/03/18 00:29, Martin Blumenstingl wrote:

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Hi Roger,

On Fri, Mar 16, 2018 at 3:32 PM, Roger Quadros [off-list ref] wrote:

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+some TI folks

Hi Martin,

On 18/02/18 20:44, Martin Blumenstingl wrote:

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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 <redacted>
Cc: Neil Armstrong <redacted>
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

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---
 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.

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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."

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+             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"

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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

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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?

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+
+     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*

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- 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

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- 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