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Message-ID: <CAGZ6i=1v6+Jt3Jecd3euNnumVK781U9DQvRz7cHWnxi8Ga6W=g@mail.gmail.com>
Date: Wed, 7 Aug 2024 12:33:08 +0800
From: Kyle Tso <kyletso@...gle.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, "raychi@...gle.com" <raychi@...gle.com>,
"badhri@...gle.com" <badhri@...gle.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "royluo@...gle.com" <royluo@...gle.com>,
"bvanassche@....org" <bvanassche@....org>, "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v3] usb: dwc3: Runtime get and put usb power_supply handle
On Wed, Aug 7, 2024 at 7:29 AM Thinh Nguyen <Thinh.Nguyen@...opsys.com> wrote:
>
> On Sun, Aug 04, 2024, Kyle Tso wrote:
> > It is possible that the usb power_supply is registered after the probe
>
> Should we defer the dwc3 probe until the power_supply is registered
> then?
>
We can do that, but getting the power_supply reference just before
using the power_supply APIs is safer because we don't risk waiting for
the registration of the usb power_supply. If vbus_draw is being called
but the usb power_supply is still not ready, just let it fail without
doing anything (only print the error logs). The usb gadget function
still works. And once the usb power_supply is ready, the vbus_draw
will be fine in following usb state changes.
Moreover, all drivers using power_supply_get_by_name in the source
tree adopt this way. IMO it should be okay.
> > of dwc3. In this case, trying to get the usb power_supply during the
> > probe will fail and there is no chance to try again. Also the usb
> > power_supply might be unregistered at anytime so that the handle of it
>
> This is problematic... If the power_supply is unregistered, the device
> is no longer usable.
>
> > in dwc3 would become invalid. To fix this, get the handle right before
> > calling to power_supply functions and put it afterward.
>
> Shouldn't the life-cycle of the dwc3 match with the power_supply? How
> can we maintain function without the proper power_supply?
>
> BR,
> Thinh
>
usb power_supply is controlled by "another" driver which can be
unloaded without notifying other drivers using it (such as dwc3).
Unless there is a notification mechanism for the (un)registration of
the power_supply class, getting/putting the reference right
before/after calling the power_supply api is the best we can do for
now.
Kyle
> >
> > dwc3_gadet_vbus_draw might be in interrupt context. Create a kthread
> > worker beforehand and use it to process the "might-sleep"
> > power_supply_put ASAP after the property set.
> >
> > Fixes: 6f0764b5adea ("usb: dwc3: add a power supply for current control")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Kyle Tso <kyletso@...gle.com>
> > ---
> > v2 -> v3:
> > - Only move power_supply_put to a work. Still call _get_by_name and
> > _set_property in dwc3_gadget_vbus_draw.
> > - Create a kthread_worker to handle the work
> >
> > v1 -> v2:
> > - move power_supply_put out of interrupt context
> >
> > drivers/usb/dwc3/core.c | 29 ++++++++++++----------------
> > drivers/usb/dwc3/core.h | 6 ++++--
> > drivers/usb/dwc3/gadget.c | 40 +++++++++++++++++++++++++++++++++++----
> > 3 files changed, 52 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 734de2a8bd21..82c8376330d7 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1631,8 +1631,6 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> > u8 tx_thr_num_pkt_prd = 0;
> > u8 tx_max_burst_prd = 0;
> > u8 tx_fifo_resize_max_num;
> > - const char *usb_psy_name;
> > - int ret;
> >
> > /* default to highest possible threshold */
> > lpm_nyet_threshold = 0xf;
> > @@ -1667,12 +1665,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> >
> > dwc->sys_wakeup = device_may_wakeup(dwc->sysdev);
> >
> > - ret = device_property_read_string(dev, "usb-psy-name", &usb_psy_name);
> > - if (ret >= 0) {
> > - dwc->usb_psy = power_supply_get_by_name(usb_psy_name);
> > - if (!dwc->usb_psy)
> > - dev_err(dev, "couldn't get usb power supply\n");
> > - }
> > + device_property_read_string(dev, "usb-psy-name", &dwc->usb_psy_name);
> >
> > dwc->has_lpm_erratum = device_property_read_bool(dev,
> > "snps,has-lpm-erratum");
> > @@ -2132,19 +2125,24 @@ static int dwc3_probe(struct platform_device *pdev)
> >
> > dwc3_get_software_properties(dwc);
> >
> > + dwc->worker = kthread_create_worker(0, "dwc3-worker");
> > + if (IS_ERR(dwc->worker))
> > + return PTR_ERR(dwc->worker);
> > + sched_set_fifo(dwc->worker->task);
> > +
> > dwc->reset = devm_reset_control_array_get_optional_shared(dev);
> > if (IS_ERR(dwc->reset)) {
> > ret = PTR_ERR(dwc->reset);
> > - goto err_put_psy;
> > + goto err_destroy_worker;
> > }
> >
> > ret = dwc3_get_clocks(dwc);
> > if (ret)
> > - goto err_put_psy;
> > + goto err_destroy_worker;
> >
> > ret = reset_control_deassert(dwc->reset);
> > if (ret)
> > - goto err_put_psy;
> > + goto err_destroy_worker;
> >
> > ret = dwc3_clk_enable(dwc);
> > if (ret)
> > @@ -2245,9 +2243,8 @@ static int dwc3_probe(struct platform_device *pdev)
> > dwc3_clk_disable(dwc);
> > err_assert_reset:
> > reset_control_assert(dwc->reset);
> > -err_put_psy:
> > - if (dwc->usb_psy)
> > - power_supply_put(dwc->usb_psy);
> > +err_destroy_worker:
> > + kthread_destroy_worker(dwc->worker);
> >
> > return ret;
> > }
> > @@ -2258,6 +2255,7 @@ static void dwc3_remove(struct platform_device *pdev)
> >
> > pm_runtime_get_sync(&pdev->dev);
> >
> > + kthread_destroy_worker(dwc->worker);
> > dwc3_core_exit_mode(dwc);
> > dwc3_debugfs_exit(dwc);
> >
> > @@ -2276,9 +2274,6 @@ static void dwc3_remove(struct platform_device *pdev)
> > pm_runtime_set_suspended(&pdev->dev);
> >
> > dwc3_free_event_buffers(dwc);
> > -
> > - if (dwc->usb_psy)
> > - power_supply_put(dwc->usb_psy);
> > }
> >
> > #ifdef CONFIG_PM
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index 1e561fd8b86e..3fc58204db6e 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -993,6 +993,7 @@ struct dwc3_scratchpad_array {
> > /**
> > * struct dwc3 - representation of our controller
> > * @drd_work: workqueue used for role swapping
> > + * @worker: dedicated kthread worker
> > * @ep0_trb: trb which is used for the ctrl_req
> > * @bounce: address of bounce buffer
> > * @setup_buf: used while precessing STD USB requests
> > @@ -1045,7 +1046,7 @@ struct dwc3_scratchpad_array {
> > * @role_sw: usb_role_switch handle
> > * @role_switch_default_mode: default operation mode of controller while
> > * usb role is USB_ROLE_NONE.
> > - * @usb_psy: pointer to power supply interface.
> > + * @usb_psy_name: name of the usb power supply interface
> > * @usb2_phy: pointer to USB2 PHY
> > * @usb3_phy: pointer to USB3 PHY
> > * @usb2_generic_phy: pointer to array of USB2 PHYs
> > @@ -1163,6 +1164,7 @@ struct dwc3_scratchpad_array {
> > */
> > struct dwc3 {
> > struct work_struct drd_work;
> > + struct kthread_worker *worker;
> > struct dwc3_trb *ep0_trb;
> > void *bounce;
> > u8 *setup_buf;
> > @@ -1223,7 +1225,7 @@ struct dwc3 {
> > struct usb_role_switch *role_sw;
> > enum usb_dr_mode role_switch_default_mode;
> >
> > - struct power_supply *usb_psy;
> > + const char *usb_psy_name;
> >
> > u32 fladj;
> > u32 ref_clk_per;
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 89fc690fdf34..1ff583281eff 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -30,6 +30,11 @@
> > #define DWC3_ALIGN_FRAME(d, n) (((d)->frame_number + ((d)->interval * (n))) \
> > & ~((d)->interval - 1))
> >
> > +struct dwc3_psy_put {
> > + struct kthread_work work;
> > + struct power_supply *psy;
> > +};
> > +
> > /**
> > * dwc3_gadget_set_test_mode - enables usb2 test modes
> > * @dwc: pointer to our context structure
> > @@ -3047,22 +3052,49 @@ static void dwc3_gadget_set_ssp_rate(struct usb_gadget *g,
> > spin_unlock_irqrestore(&dwc->lock, flags);
> > }
> >
> > +static void dwc3_gadget_psy_put(struct kthread_work *work)
> > +{
> > + struct dwc3_psy_put *psy_put = container_of(work, struct dwc3_psy_put, work);
> > +
> > + power_supply_put(psy_put->psy);
> > + kfree(psy_put);
> > +}
> > +
> > static int dwc3_gadget_vbus_draw(struct usb_gadget *g, unsigned int mA)
> > {
> > - struct dwc3 *dwc = gadget_to_dwc(g);
> > + struct dwc3 *dwc = gadget_to_dwc(g);
> > + struct power_supply *usb_psy;
> > union power_supply_propval val = {0};
> > + struct dwc3_psy_put *psy_put;
> > int ret;
> >
> > if (dwc->usb2_phy)
> > return usb_phy_set_power(dwc->usb2_phy, mA);
> >
> > - if (!dwc->usb_psy)
> > + if (!dwc->usb_psy_name)
> > return -EOPNOTSUPP;
> >
> > + usb_psy = power_supply_get_by_name(dwc->usb_psy_name);
> > + if (!usb_psy) {
> > + dev_err(dwc->dev, "couldn't get usb power supply\n");
> > + return -ENODEV;
> > + }
> > +
> > val.intval = 1000 * mA;
> > - ret = power_supply_set_property(dwc->usb_psy, POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, &val);
> > + ret = power_supply_set_property(usb_psy, POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, &val);
> > + if (ret < 0) {
> > + dev_err(dwc->dev, "failed to set power supply property\n");
> > + return ret;
> > + }
> >
> > - return ret;
> > + psy_put = kzalloc(sizeof(*psy_put), GFP_ATOMIC);
> > + if (!psy_put)
> > + return -ENOMEM;
> > + kthread_init_work(&psy_put->work, dwc3_gadget_psy_put);
> > + psy_put->psy = usb_psy;
> > + kthread_queue_work(dwc->worker, &psy_put->work);
> > +
> > + return 0;
> > }
> >
> > /**
> > --
> > 2.46.0.rc2.264.g509ed76dc8-goog
> >
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