Re: [PATCH v2 10/10] usb: dwc2/gadget: rework suspend/resume code to correctly restore gadget state

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On 2014-10-27 08:18, Marek Szyprowski wrote:
>
> On 2014-10-25 03:16, Paul Zimmerman wrote:
>>> From: Marek Szyprowski [mailto:m.szyprowski@samsung.com]
>>> Sent: Monday, October 20, 2014 3:46 AM
>>>
>>> Suspend/resume code assumed that the gadget was always enabled and
>>> connected to usb bus. This means that the actual state of the gadget
>>> (soft-enabled/disabled or connected/disconnected) was not correctly
>>> preserved on suspend/resume cycle. This patch fixes this issue.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   drivers/usb/dwc2/core.h   |  4 +++-
>>>   drivers/usb/dwc2/gadget.c | 43 
>>> +++++++++++++++++++++++++++----------------
>>>   2 files changed, 30 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
>>> index bf015ab3b44c..3648b76a18b4 100644
>>> --- a/drivers/usb/dwc2/core.h
>>> +++ b/drivers/usb/dwc2/core.h
>>> @@ -210,7 +210,9 @@ struct s3c_hsotg {
>>>       u8                      ctrl_buff[8];
>>>
>>>       struct usb_gadget       gadget;
>>> -    unsigned int            setup;
>>> +    unsigned int            setup:1;
>>> +    unsigned int        connected:1;
>>> +    unsigned int        enabled:1;
>>>       unsigned long           last_rst;
>>>       struct s3c_hsotg_ep     *eps;
>>>   };
>>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
>>> index 0d34cfc71bfb..c6c6cf982c90 100644
>>> --- a/drivers/usb/dwc2/gadget.c
>>> +++ b/drivers/usb/dwc2/gadget.c
>>> @@ -2925,6 +2925,8 @@ static int s3c_hsotg_udc_start(struct 
>>> usb_gadget *gadget,
>>>       spin_lock_irqsave(&hsotg->lock, flags);
>>>       s3c_hsotg_init(hsotg);
>>>       s3c_hsotg_core_init_disconnected(hsotg);
>>> +    hsotg->enabled = 1;
>>> +    hsotg->connected = 0;
>>>       spin_unlock_irqrestore(&hsotg->lock, flags);
>>>
>>>       dev_info(hsotg->dev, "bound driver %s\n", driver->driver.name);
>>> @@ -2961,6 +2963,8 @@ static int s3c_hsotg_udc_stop(struct 
>>> usb_gadget *gadget,
>>>
>>>       hsotg->driver = NULL;
>>>       hsotg->gadget.speed = USB_SPEED_UNKNOWN;
>>> +    hsotg->enabled = 0;
>>> +    hsotg->connected = 0;
>>>
>>>       spin_unlock_irqrestore(&hsotg->lock, flags);
>>>
>>> @@ -2999,11 +3003,14 @@ static int s3c_hsotg_pullup(struct 
>>> usb_gadget *gadget, int is_on)
>>>       dev_dbg(hsotg->dev, "%s: is_on: %d\n", __func__, is_on);
>>>
>>>       spin_lock_irqsave(&hsotg->lock, flags);
>>> +
>>>       if (is_on) {
>>>           clk_enable(hsotg->clk);
>>> +        hsotg->connected = 1;
>>>           s3c_hsotg_core_connect(hsotg);
>>>       } else {
>>>           s3c_hsotg_core_disconnect(hsotg);
>>> +        hsotg->connected = 0;
>>>           clk_disable(hsotg->clk);
>>>       }
>>>
>>> @@ -3652,16 +3659,18 @@ static int s3c_hsotg_suspend(struct 
>>> platform_device *pdev, pm_message_t state)
>>>           dev_info(hsotg->dev, "suspending usb gadget %s\n",
>>>                hsotg->driver->driver.name);
>>>
>>> -    spin_lock_irqsave(&hsotg->lock, flags);
>>> -    s3c_hsotg_core_disconnect(hsotg);
>>> -    s3c_hsotg_disconnect(hsotg);
>>> -    hsotg->gadget.speed = USB_SPEED_UNKNOWN;
>>> -    spin_unlock_irqrestore(&hsotg->lock, flags);
>>> +    if (hsotg->enabled) {
>> Hmm. Are you sure it's safe to check ->enabled outside of the spinlock?
>> What happens if s3c_hsotg_udc_stop() runs right after this, before the
>> spinlock is taken, and disables stuff? Sure, it's a tiny window, but
>> still...
>
> This code is called only in system suspend path, when userspace has 
> been already frozen.
> udc_stop() can be called only as a result of userspace action, so it 
> is imho safe to
> assume that the above code doesn't need additional locking.

However if you prefer the version with explicit locking, I will send v3 
in a few minutes.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland