linux-kernel - Re: [PATCH v2] usb: dwc2: call dwc2_is_controller

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Date:	Wed, 14 Jan 2015 13:37:54 -0600
From:	Felipe Balbi <balbi@...com>
To:	Robert Baldyga <r.baldyga@...sung.com>
CC:	<paulz@...opsys.com>, <balbi@...com>, <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<dinguyen@...nsource.altera.com>, <yousaf.kaukab@...el.com>,
	<m.szyprowski@...sung.com>
Subject: Re: [PATCH v2] usb: dwc2: call dwc2_is_controller_alive() under
 spinlock

On Wed, Jan 14, 2015 at 07:45:31AM +0100, Robert Baldyga wrote:
> This patch fixes bug described here:
> https://lkml.org/lkml/2014/12/22/185
> 
> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
> ---
> 
> Changelog:
> 
> v2:
> - fixed comment from Paul Zimmerman
> 
> v1: https://lkml.org/lkml/2015/1/13/186
> 
>  drivers/usb/dwc2/core_intr.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc2/core_intr.c b/drivers/usb/dwc2/core_intr.c
> index ad43c5b..02e3e2d 100644
> --- a/drivers/usb/dwc2/core_intr.c
> +++ b/drivers/usb/dwc2/core_intr.c
> @@ -476,13 +476,13 @@ irqreturn_t dwc2_handle_common_intr(int irq, void *dev)
>  	u32 gintsts;
>  	irqreturn_t retval = IRQ_NONE;
>  
> +	spin_lock(&hsotg->lock);
> +
>  	if (!dwc2_is_controller_alive(hsotg)) {

This is really, really odd. Register accesses are atomic, so the lock
isn't really doing anything. Besides, you're calling
dwc2_is_controller_alive() from within the IRQ handler, so IRQs are
already disabled.

When the problem happens, do you see this "Controller is dead" message ?

-- 
balbi

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