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

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Date:	Thu, 12 May 2016 05:53:15 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Wenyou Yang <wenyou.yang@...el.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nicolas Ferre <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?

> 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.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com