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Message-ID: <20240916211819.ulvmre4o57bhrr6q@synopsys.com>
Date: Mon, 16 Sep 2024 21:18:13 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Selvarasu Ganesan <selvarasu.g@...sung.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jh0801.jung@...sung.com" <jh0801.jung@...sung.com>,
"dh10.jung@...sung.com" <dh10.jung@...sung.com>,
"naushad@...sung.com" <naushad@...sung.com>,
"akash.m5@...sung.com" <akash.m5@...sung.com>,
"rc93.raju@...sung.com" <rc93.raju@...sung.com>,
"taehyun.cho@...sung.com" <taehyun.cho@...sung.com>,
"hongpooh.kim@...sung.com" <hongpooh.kim@...sung.com>,
"eomji.oh@...sung.com" <eomji.oh@...sung.com>,
"shijie.cai@...sung.com" <shijie.cai@...sung.com>
Subject: Re: [PATCH] usb: dwc3: Potential fix of possible dwc3 interrupt storm
On Mon, Sep 16, 2024, Selvarasu Ganesan wrote:
>
> On 9/13/2024 11:21 PM, Thinh Nguyen wrote:
> > Hi,
> >
> > On Fri, Sep 13, 2024, Selvarasu Ganesan wrote:
> >> Hi Thinh,
> >>
> >> So far, there have been no reported error instances. But, we suspecting
> >> that the issue may be related to our glue driver. In our glue driver, we
> >> access the reference of evt->flags when starting or stopping the gadget
> >> based on a VBUS notification. We apologize for sharing this information
> >> so late, as we only became aware of it recently.
> >>
> >> The following sequence outlines the possible scenarios of race conditions:
> >>
> >> Thread#1 (Our glue Driver Sequence)
> >> ===================================
> >> ->USB VBUS notification
> >> ->Start/Stop gadget
> >> ->dwc->ev_buf->flags |= BIT(20); (It's for our reference)
> >> ->Call dwc3 exynos runtime suspend/resume
> >> ->dwc->ev_buf->flags &= ~BIT(20);
> >> ->Call dwc3 core runtime suspend/resume
> >>
> >> Thread#2
> >> ========
> >> ->dwc3_interrupt()
> >> ->evt->flags |= DWC3_EVENT_PENDING;
> >> ->dwc3_thread_interrupt()
> >> ->evt->flags &= ~DWC3_EVENT_PENDING;
> >>
> > This is great! That's likely the problem. Glad you found it.
> >
> >>
> >> After our internal discussions, we have decided to remove the
> >> unnecessary access to evt->flag in our glue driver. We have made these
> >> changes and initiated testing.
> >>
> >> Thank you for your help so far to understand more into our glue driver code.
> >>
> >> And We are thinking that it would be fine to reset evt->flag when the
> >> USB controller is started, along with the changes you suggested earlier.
> >> This additional measure will help prevent similar issues from occurring
> >> in the future.
> >>
> >> Please let us know your thoughts on this proposal. If it is not
> >> necessary, we understand and will proceed accordingly.
> >>
> > You can submit the change I suggested. That's a valid change. However,
> > we should not include the reset of the DWC3_EVENT_PENDING flag. Had we
> > done this, you may not found the issue above. It serves no purpose for
> > the core driver logic and will be an extra burden for us to maintain. (I
> > don't want to scratch my head in the future to figure out why that
> > change was needed or concern whether it can be removed without causing
> > regression).
>
> Yeah I understand.
>
> Please reconfirm the below changes once with commit message. I will post
> new version if this changes are fine.
>
>
> [PATCH] usb: dwc3: core: Stop processing of pending events if controller
> is halted
>
> This commit addresses an issue where events were being processed when
> the controller was in a halted state. To fix this issue by stop
> processing the events as the event count was considered stale or
> invalid when the controller was halted.
>
> Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Selvarasu Ganesan <selvarasu.g@...sung.com>
> Suggested-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
> ---
> drivers/usb/dwc3/core.c | 17 +++++++++++++++--
> drivers/usb/dwc3/core.h | 4 ----
> drivers/usb/dwc3/gadget.c | 22 +++++++++++-----------
> 3 files changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 9eb085f359ce..f47b20bc2d1f 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -544,6 +544,7 @@ static int dwc3_alloc_event_buffers(struct dwc3
> *dwc, unsigned int length)
> int dwc3_event_buffers_setup(struct dwc3 *dwc)
> {
> struct dwc3_event_buffer *evt;
> + u32 reg;
>
> if (!dwc->ev_buf)
> return 0;
> @@ -556,8 +557,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
> upper_32_bits(evt->dma));
> dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0),
> DWC3_GEVNTSIZ_SIZE(evt->length));
> - dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 0);
>
> + /* Clear any stale event */
Do the same thing here as in dwc3_event_buffers_cleanup().
> + reg = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
> + dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), reg);
> return 0;
> }
>
> @@ -2499,7 +2502,11 @@ static int dwc3_runtime_resume(struct device *dev)
>
> switch (dwc->current_dr_role) {
> case DWC3_GCTL_PRTCAP_DEVICE:
> - dwc3_gadget_process_pending_events(dwc);
> + if (dwc->pending_events) {
> + pm_runtime_put(dwc->dev);
> + dwc->pending_events = false;
> + enable_irq(dwc->irq_gadget);
> + }
> break;
> case DWC3_GCTL_PRTCAP_HOST:
> default:
> @@ -2589,6 +2596,12 @@ static void dwc3_complete(struct device *dev)
> static const struct dev_pm_ops dwc3_dev_pm_ops = {
> SET_SYSTEM_SLEEP_PM_OPS(dwc3_suspend, dwc3_resume)
> .complete = dwc3_complete,
> +
> + /*
> + * Runtime suspend halts the controller on disconnection. It
> replies on
> + * platforms with custom connection notification to start the
> controller
> + * again.
> + */
> SET_RUNTIME_PM_OPS(dwc3_runtime_suspend, dwc3_runtime_resume,
> dwc3_runtime_idle)
> };
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index c71240e8f7c7..9c508e0c5cdf 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1675,7 +1675,6 @@ static inline void dwc3_otg_host_init(struct dwc3
> *dwc)
> #if !IS_ENABLED(CONFIG_USB_DWC3_HOST)
> int dwc3_gadget_suspend(struct dwc3 *dwc);
> int dwc3_gadget_resume(struct dwc3 *dwc);
> -void dwc3_gadget_process_pending_events(struct dwc3 *dwc);
> #else
> static inline int dwc3_gadget_suspend(struct dwc3 *dwc)
> {
> @@ -1687,9 +1686,6 @@ static inline int dwc3_gadget_resume(struct dwc3 *dwc)
> return 0;
> }
>
> -static inline void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
> -{
> -}
> #endif /* !IS_ENABLED(CONFIG_USB_DWC3_HOST) */
>
> #if IS_ENABLED(CONFIG_USB_DWC3_ULPI)
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 291bc549935b..a32c3a292353 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4483,6 +4483,17 @@ static irqreturn_t dwc3_check_event_buf(struct
> dwc3_event_buffer *evt)
> return IRQ_HANDLED;
>
> count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
If we properly cleanup event count in dwc3_event_buffers_cleanup() as
noted above, then you don't need this condition below. You can remove
the below check:
> +
> + /*
> + * If the controller is halted, the event count is
> stale/invalid. Ignore
> + * them. This happens if the interrupt assertion is from an
> out-of-band
> + * resume notification.
> + */
> + if (!dwc->pullups_connected && count) {
> + dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
> + return IRQ_HANDLED;
> + }
> +
> count &= DWC3_GEVNTCOUNT_MASK;
> if (!count)
> return IRQ_NONE;
> @@ -4728,14 +4739,3 @@ int dwc3_gadget_resume(struct dwc3 *dwc)
>
> return dwc3_gadget_soft_connect(dwc);
> }
> -
> -void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
> -{
> - if (dwc->pending_events) {
> - dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
> - dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
> - pm_runtime_put(dwc->dev);
> - dwc->pending_events = false;
> - enable_irq(dwc->irq_gadget);
> - }
> -}
The rest looks fine.
Thanks,
Thinh
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