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 15:11:51 +0300
From:	Felipe Balbi <balbi@...com>
To:	Roger Quadros <rogerq@...com>
CC:	<stern@...land.harvard.edu>, <tony@...mide.com>, <balbi@...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

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);
		omap->flags &= ~OMAP_EHCI_IRQ_PENDING;
	}

	return 0;
}

or something similar

-- 
balbi

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