Re: [PATCH] usb: ehci-brcm: fix sleep during atomic

[Florian Fainelli <florian.fainelli@broadcom.com>]

On 3/18/26 09:31, Justin Chen wrote:
> 
> 
> On 3/18/2026 7:14 AM, Greg KH wrote:
>> On Thu, Mar 12, 2026 at 12:08:25PM -0700, justin.chen@broadcom.com wrote:
>>> From: Justin Chen <justin.chen@broadcom.com>
>>>
>>> echi_brcm_wait_for_sof() gets called after disabling interrupts
>>> in ehci_brcm_hub_control(). Use the atomic version of poll_timeout
>>> to fix the warning.
>>>
>>> Fixes: ("9df231511bd6 usb: ehci: Add new EHCI driver for Broadcom STB 
>>> SoC's")
>>> Signed-off-by: Justin Chen <justin.chen@broadcom.com>
>>> ---
>>>   drivers/usb/host/ehci-brcm.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/usb/host/ehci-brcm.c b/drivers/usb/host/ehci-brcm.c
>>> index 888e8f6670d2..5e3156f94cc6 100644
>>> --- a/drivers/usb/host/ehci-brcm.c
>>> +++ b/drivers/usb/host/ehci-brcm.c
>>> @@ -31,8 +31,8 @@ static inline void ehci_brcm_wait_for_sof(struct 
>>> ehci_hcd *ehci, u32 delay)
>>>       int res;
>>>       /* Wait for next microframe (every 125 usecs) */
>>> -    res = readl_relaxed_poll_timeout(&ehci->regs->frame_index, val,
>>> -                     val != frame_idx, 1, 130);
>>> +    res = readl_relaxed_poll_timeout_atomic(&ehci->regs->frame_index,
>>> +                        val, val != frame_idx, 1, 130);
>>>       if (res)
>>>           ehci_err(ehci, "Error waiting for SOF\n");
>>>       udelay(delay);
>>> -- 
>>> 2.34.1
>>>
>>>
>>
>> Why is something that has been around for so long just now suddenly
>> being seen?  What changed to trigger this?
>>
> 
> The edge case occurs in rare occasions and predates my time maintaining 
> this driver. So we just so happened to run into it recently in our 
> tests. Guess in the past we just never hit the edge case with the 
> warnings enabled. I had the same question when the warning was reported.
> 
> Will fix the Fixes tag in v2.

The other thing is that recently enabled CONFIG_DEBUG_SLEEP_ATOMIC in 
our builds which is how this got caught, it was not the case before.
-- 
Florian