linux-kernel - Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during bus suspend

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Date:	Thu, 20 Jun 2013 15:35:22 +0300
From:	Roger Quadros <rogerq@...com>
To:	<balbi@...com>
CC:	<stern@...land.harvard.edu>, <tony@...mide.com>,
	<ruslan.bilovol@...com>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during
 bus suspend

On 06/20/2013 03:11 PM, Felipe Balbi wrote:
> Hi,
> 
> On Wed, Jun 19, 2013 at 05:05:51PM +0300, Roger Quadros wrote:
>> Runtime suspend the controller during bus suspend and resume it
>> during bus resume. This will ensure that the USB Host power domain
>> enters lower power state and does not prevent the SoC from
>> endering deeper sleep states.
>>
>> Remote wakeup will come up as an interrupt while the controller
>> is suspended, so tackle it carefully using a workqueue.
>>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>  drivers/usb/host/ehci-omap.c |   82 ++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 82 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/usb/host/ehci-omap.c b/drivers/usb/host/ehci-omap.c
>> index 16d7150..91f14f1 100644
>> --- a/drivers/usb/host/ehci-omap.c
>> +++ b/drivers/usb/host/ehci-omap.c
>> @@ -44,6 +44,8 @@
>>  #include <linux/usb/hcd.h>
>>  #include <linux/of.h>
>>  #include <linux/dma-mapping.h>
>> +#include <linux/workqueue.h>
>> +#include <linux/spinlock.h>
>>  
>>  #include "ehci.h"
>>  
>> @@ -69,6 +71,7 @@ static const char hcd_name[] = "ehci-omap";
>>  struct omap_hcd {
>>  	struct usb_phy *phy[OMAP3_HS_USB_PORTS]; /* one PHY for each port */
>>  	int nports;
>> +	struct work_struct work;
>>  };
>>  
>>  static inline void ehci_write(void __iomem *base, u32 reg, u32 val)
>> @@ -81,6 +84,76 @@ static inline u32 ehci_read(void __iomem *base, u32 reg)
>>  	return __raw_readl(base + reg);
>>  }
>>  
>> +static void omap_ehci_work(struct work_struct *work)
>> +{
>> +	struct omap_hcd *omap = container_of(work, struct omap_hcd, work);
>> +	struct ehci_hcd *ehci = container_of((void *) omap,
>> +						struct ehci_hcd, priv);
>> +	struct usb_hcd *hcd = ehci_to_hcd(ehci);
>> +	struct device *dev = hcd->self.controller;
>> +
>> +	pm_runtime_get_sync(dev);
>> +	enable_irq(hcd->irq);
>> +	/*
>> +	 * enable_irq() should preempt us with a pending IRQ
>> +	 * so we can be sure that IRQ handler completes before
>> +	 * we call pm_runtime_put_sync()
>> +	 */
>> +	pm_runtime_put_sync(dev);
>> +}
>> +
>> +static irqreturn_t omap_ehci_irq(struct usb_hcd *hcd)
>> +{
>> +	struct omap_hcd *omap = (struct omap_hcd *)hcd_to_ehci(hcd)->priv;
>> +	struct device *dev = hcd->self.controller;
>> +	irqreturn_t ret;
>> +
>> +	if (pm_runtime_suspended(dev)) {
>> +		schedule_work(&omap->work);
>> +		disable_irq_nosync(hcd->irq);
>> +		ret = IRQ_HANDLED;
> 
> looks like this could be done as:
> 
> if (pm_runtime_suspended(dev)) {
> 	pm_runtime_get(dev);
> 	omap->flags |= OMAP_EHCI_IRQ_PENDING;
> 	disable_irq_nosync(hcd->irq);
> 	ret = IRQ_HANDLED;
> }
> 
> then on your ->runtime_resume():
> 
> runtime_resume(dev)
> {
> 	...
> 
> 	if (omap->flags & OMAP_EHCI_IRQ_PENDING) {
> 		process_pending_irqs(omap);

OK, thanks. 

But I'm not sure if the generic ehci_irq handler is able to
run in a process context. Maybe if we replace spin_lock(&ehci->lock);
with spin_lock_irqsave() there, it will work.

Alan is this a doable option?

> 		omap->flags &= ~OMAP_EHCI_IRQ_PENDING;
> 	}
> 
> 	return 0;
> }
> 
> or something similar
> 

cheers,
-roger
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