linux-kernel - RE: [PATCH] usb: ohci-at91: Suspend the ports while USB suspending

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Date:	Thu, 12 May 2016 05:50:18 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] usb: ohci-at91: Suspend the ports while USB suspending



> -----Original Message-----
> From: Alexandre Belloni [mailto:alexandre.belloni@...e-electrons.com]
> Sent: 2016年5月12日 11:53
> To: Yang, Wenyou <Wenyou.Yang@...el.com>
> Cc: Alan Stern <stern@...land.harvard.edu>; Greg Kroah-Hartman
> <gregkh@...uxfoundation.org>; Ferre, Nicolas <Nicolas.FERRE@...el.com>;
> linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH] usb: ohci-at91: Suspend the ports while USB suspending
> 
> Hi,
> 
> On 12/05/2016 at 09:05:34 +0800, Wenyou Yang wrote :
> > In order to get lower consumption, as a workaround, suspend the USB
> > PORTA/B/C via set the SUSPEND_A/B/C bits of OHCI Interrupt
> > Configuration Register while OHCI USB suspending.
> >
> 
> Why is that a workaround?

Because if these bits is not set as this patch, there is 5mA current left
at VDDOSC rail during suspend. If apply this patch, this current will disappear.

So, I think it is a workaround.

> 
> > This suspend operation must be done before stopping the USB clock,
> > resume after the USB clock enabled.
> >
> > Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> > ---
> >
> >  drivers/usb/host/ohci-at91.c | 63
> > ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 63 insertions(+)
> >
> > diff --git a/drivers/usb/host/ohci-at91.c
> > b/drivers/usb/host/ohci-at91.c index d177372..ce898e0 100644
> > --- a/drivers/usb/host/ohci-at91.c
> > +++ b/drivers/usb/host/ohci-at91.c
> > @@ -21,6 +21,8 @@
> >  #include <linux/io.h>
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> > +#include <linux/mfd/syscon.h>
> > +#include <linux/regmap.h>
> >  #include <linux/usb.h>
> >  #include <linux/usb/hcd.h>
> >
> > @@ -51,6 +53,7 @@ struct ohci_at91_priv {
> >  	struct clk *hclk;
> >  	bool clocked;
> >  	bool wakeup;		/* Saved wake-up state for resume */
> > +	struct regmap *sfr_regmap;
> >  };
> >  /* interface and function clocks; sometimes also an AHB clock */
> >
> > @@ -132,6 +135,17 @@ static void at91_stop_hc(struct platform_device
> > *pdev)
> >
> >
> > /*--------------------------------------------------------------------
> > -----*/
> >
> > +struct regmap *at91_dt_syscon_sfr(void) {
> > +	struct regmap *regmap;
> > +
> > +	regmap = syscon_regmap_lookup_by_compatible("atmel,sama5d2-sfr");
> > +	if (IS_ERR(regmap))
> > +		return NULL;
> > +
> > +	return regmap;
> > +}
> > +
> >  static void usb_hcd_at91_remove (struct usb_hcd *, struct
> > platform_device *);
> >
> >  /* configure so an HC device and id are always provided */ @@ -197,6
> > +211,8 @@ static int usb_hcd_at91_probe(const struct hc_driver *driver,
> >  		goto err;
> >  	}
> >
> > +	ohci_at91->sfr_regmap = at91_dt_syscon_sfr();
> > +
> >  	board = hcd->self.controller->platform_data;
> >  	ohci = hcd_to_ohci(hcd);
> >  	ohci->num_ports = board->ports;
> > @@ -581,6 +597,49 @@ static int ohci_hcd_at91_drv_remove(struct
> platform_device *pdev)
> >  	return 0;
> >  }
> >
> > +#define SFR_OHCIICR		0x10
> > +#define SFR_OHCIICR_SUSPEND_A	BIT(8)
> > +#define SFR_OHCIICR_SUSPEND_B	BIT(9)
> > +#define SFR_OHCIICR_SUSPEND_C	BIT(10)
> > +
> > +#define SFR_OHCIICR_USB_SUSPEND	(SFR_OHCIICR_SUSPEND_A | \
> > +				 SFR_OHCIICR_SUSPEND_B | \
> > +				 SFR_OHCIICR_SUSPEND_C)
> > +
> 
> Those defines should go in a header file either in include/soc/at91 or in
> include/linux/mfd
> 
> > +static int ohci_at91_port_ctrl(struct regmap *regmap, bool enable) {
> > +	u32 regval;
> > +	int ret;
> > +
> > +	if (IS_ERR(regmap))
> > +		return PTR_ERR(regmap);
> > +
> > +	ret = regmap_read(regmap, SFR_OHCIICR, &regval);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (enable)
> > +		regval &= ~SFR_OHCIICR_USB_SUSPEND;
> > +	else
> > +		regval |= SFR_OHCIICR_USB_SUSPEND;
> > +
> > +	regmap_write(regmap, SFR_OHCIICR, regval);
> > +
> > +	regmap_read(regmap, SFR_OHCIICR, &regval);
> > +
> > +	return 0;
> > +}
> > +
> > +static int ohci_at91_port_suspend(struct regmap *regmap) {
> > +	return ohci_at91_port_ctrl(regmap, false); }
> > +
> > +static int ohci_at91_port_resume(struct regmap *regmap) {
> > +	return ohci_at91_port_ctrl(regmap, true); }
> > +
> >  static int __maybe_unused
> >  ohci_hcd_at91_drv_suspend(struct device *dev)  { @@ -618,6 +677,8 @@
> > ohci_hcd_at91_drv_suspend(struct device *dev)
> >  		ohci_writel(ohci, ohci->hc_control, &ohci->regs->control);
> >  		ohci->rh_state = OHCI_RH_HALTED;
> >
> > +		ohci_at91_port_suspend(ohci_at91->sfr_regmap);
> > +
> 
> The main issue I see here is that you will call that function for all SoCs and it will
> always fail unless it is running on a sama5d2. Maybe we could be smarter about
> that.

Can we use another compatible, such as "atmel,sama5d2-ohci" to differentiate it? 


Best Regards,
Wenyou Yang