Re: [PATCH v2 2/8] usb: phy: tegra: Support waking up from a low power mode

[Thierry Reding <thierry.reding@gmail.com>]

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On Thu, Dec 17, 2020 at 12:40:01PM +0300, Dmitry Osipenko wrote:
> Support programming of waking up from a low power mode by implementing the
> generic set_wakeup() callback of the USB PHY API.
> 
> Tested-by: Matt Merhar <mattmerhar@protonmail.com>
> Tested-by: Nicolas Chauvet <kwizart@gmail.com>
> Tested-by: Peter Geis <pgwipeout@gmail.com>
> Tested-by: Ion Agorria <ion@agorria.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/usb/phy/phy-tegra-usb.c   | 94 +++++++++++++++++++++++++++++--
>  include/linux/usb/tegra_usb_phy.h |  2 +
>  2 files changed, 90 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/phy/phy-tegra-usb.c b/drivers/usb/phy/phy-tegra-usb.c
> index 1296524e1bee..46a1f61877ad 100644
> --- a/drivers/usb/phy/phy-tegra-usb.c
> +++ b/drivers/usb/phy/phy-tegra-usb.c
> @@ -45,6 +45,7 @@
>  #define TEGRA_PORTSC1_RWC_BITS	(PORT_CSC | PORT_PEC | PORT_OCC)
>  
>  #define USB_SUSP_CTRL				0x400
> +#define   USB_WAKE_ON_RESUME_EN			BIT(2)
>  #define   USB_WAKE_ON_CNNT_EN_DEV		BIT(3)
>  #define   USB_WAKE_ON_DISCON_EN_DEV		BIT(4)
>  #define   USB_SUSP_CLR				BIT(5)
> @@ -56,6 +57,15 @@
>  #define   USB_SUSP_SET				BIT(14)
>  #define   USB_WAKEUP_DEBOUNCE_COUNT(x)		(((x) & 0x7) << 16)
>  
> +#define USB_PHY_VBUS_SENSORS			0x404
> +#define   B_SESS_VLD_WAKEUP_EN			BIT(6)
> +#define   B_VBUS_VLD_WAKEUP_EN			BIT(14)
> +#define   A_SESS_VLD_WAKEUP_EN			BIT(22)
> +#define   A_VBUS_VLD_WAKEUP_EN			BIT(30)
> +
> +#define USB_PHY_VBUS_WAKEUP_ID			0x408
> +#define   VBUS_WAKEUP_WAKEUP_EN			BIT(30)
> +
>  #define USB1_LEGACY_CTRL			0x410
>  #define   USB1_NO_LEGACY_MODE			BIT(0)
>  #define   USB1_VBUS_SENSE_CTL_MASK		(3 << 1)
> @@ -334,6 +344,11 @@ static int utmip_pad_power_on(struct tegra_usb_phy *phy)
>  		writel_relaxed(val, base + UTMIP_BIAS_CFG0);
>  	}
>  
> +	if (phy->pad_wakeup) {
> +		phy->pad_wakeup = false;
> +		utmip_pad_count--;
> +	}
> +
>  	spin_unlock(&utmip_pad_lock);
>  
>  	clk_disable_unprepare(phy->pad_clk);
> @@ -359,6 +374,17 @@ static int utmip_pad_power_off(struct tegra_usb_phy *phy)
>  		goto ulock;
>  	}
>  
> +	/*
> +	 * In accordance to TRM, OTG and Bias pad circuits could be turned off
> +	 * to save power if wake is enabled, but the VBUS-change detection
> +	 * method is board-specific and these circuits may need to be enabled
> +	 * to generate wakeup event, hence we will just keep them both enabled.
> +	 */
> +	if (phy->wakeup_enabled) {
> +		phy->pad_wakeup = true;
> +		utmip_pad_count++;
> +	}
> +
>  	if (--utmip_pad_count == 0) {
>  		val = readl_relaxed(base + UTMIP_BIAS_CFG0);
>  		val |= UTMIP_OTGPD | UTMIP_BIASPD;
> @@ -503,11 +529,24 @@ static int utmi_phy_power_on(struct tegra_usb_phy *phy)
>  		writel_relaxed(val, base + UTMIP_PLL_CFG1);
>  	}
>  
> +	val = readl_relaxed(base + USB_SUSP_CTRL);
> +	val &= ~USB_WAKE_ON_RESUME_EN;
> +	writel_relaxed(val, base + USB_SUSP_CTRL);
> +
>  	if (phy->mode == USB_DR_MODE_PERIPHERAL) {
>  		val = readl_relaxed(base + USB_SUSP_CTRL);
>  		val &= ~(USB_WAKE_ON_CNNT_EN_DEV | USB_WAKE_ON_DISCON_EN_DEV);
>  		writel_relaxed(val, base + USB_SUSP_CTRL);
>  
> +		val = readl_relaxed(base + USB_PHY_VBUS_WAKEUP_ID);
> +		val &= ~VBUS_WAKEUP_WAKEUP_EN;
> +		writel_relaxed(val, base + USB_PHY_VBUS_WAKEUP_ID);
> +
> +		val = readl_relaxed(base + USB_PHY_VBUS_SENSORS);
> +		val &= ~(A_VBUS_VLD_WAKEUP_EN | A_SESS_VLD_WAKEUP_EN);
> +		val &= ~(B_VBUS_VLD_WAKEUP_EN | B_SESS_VLD_WAKEUP_EN);
> +		writel_relaxed(val, base + USB_PHY_VBUS_SENSORS);
> +
>  		val = readl_relaxed(base + UTMIP_BAT_CHRG_CFG0);
>  		val &= ~UTMIP_PD_CHRG;
>  		writel_relaxed(val, base + UTMIP_BAT_CHRG_CFG0);
> @@ -605,31 +644,55 @@ static int utmi_phy_power_off(struct tegra_usb_phy *phy)
>  
>  	utmi_phy_clk_disable(phy);
>  
> -	if (phy->mode == USB_DR_MODE_PERIPHERAL) {
> -		val = readl_relaxed(base + USB_SUSP_CTRL);
> -		val &= ~USB_WAKEUP_DEBOUNCE_COUNT(~0);
> -		val |= USB_WAKE_ON_CNNT_EN_DEV | USB_WAKEUP_DEBOUNCE_COUNT(5);
> -		writel_relaxed(val, base + USB_SUSP_CTRL);
> -	}
> +	/* PHY won't resume if reset is asserted */
> +	if (phy->wakeup_enabled)
> +		goto chrg_cfg0;
>  
>  	val = readl_relaxed(base + USB_SUSP_CTRL);
>  	val |= UTMIP_RESET;
>  	writel_relaxed(val, base + USB_SUSP_CTRL);
>  
> +chrg_cfg0:

I found this diffcult to read until I realized that it was basically
just the equivalent of this:

	if (!phy->wakeup_enabled) {
		val = readl_relaxed(base + USB_SUSP_CTRL);
		val |= UTMIP_RESET;
		writel_relaxed(val, base + USB_SUSP_CTRL);
	}

>  	val = readl_relaxed(base + UTMIP_BAT_CHRG_CFG0);
>  	val |= UTMIP_PD_CHRG;
>  	writel_relaxed(val, base + UTMIP_BAT_CHRG_CFG0);
>  
> +	if (phy->wakeup_enabled)
> +		goto xcvr_cfg1;
> +
>  	val = readl_relaxed(base + UTMIP_XCVR_CFG0);
>  	val |= UTMIP_FORCE_PD_POWERDOWN | UTMIP_FORCE_PD2_POWERDOWN |
>  	       UTMIP_FORCE_PDZI_POWERDOWN;
>  	writel_relaxed(val, base + UTMIP_XCVR_CFG0);
>  
> +xcvr_cfg1:

Similarly, I think this is more readable as:

	if (!phy->wakeup_enabled) {
		val = readl_relaxed(base + UTMIP_XCVR_CFG0);
		val |= UTMIP_FORCE_PD_POWERDOWN | UTMIP_FORCE_PD2_POWERDOWN |
		       UTMIP_FORCE_PDZI_POWERDOWN;
		writel_relaxed(val, base + UTMIP_XCVR_CFG0);
	}

>  	val = readl_relaxed(base + UTMIP_XCVR_CFG1);
>  	val |= UTMIP_FORCE_PDDISC_POWERDOWN | UTMIP_FORCE_PDCHRP_POWERDOWN |
>  	       UTMIP_FORCE_PDDR_POWERDOWN;
>  	writel_relaxed(val, base + UTMIP_XCVR_CFG1);
>  
> +	if (phy->wakeup_enabled) {

Which then also matches the style of this conditional here.

> +		val = readl_relaxed(base + USB_SUSP_CTRL);
> +		val &= ~USB_WAKEUP_DEBOUNCE_COUNT(~0);
> +		val |= USB_WAKEUP_DEBOUNCE_COUNT(5);
> +		val |= USB_WAKE_ON_RESUME_EN;
> +		writel_relaxed(val, base + USB_SUSP_CTRL);
> +
> +		/*
> +		 * Ask VBUS sensor to generate wake event once cable is
> +		 * connected.
> +		 */
> +		if (phy->mode == USB_DR_MODE_PERIPHERAL) {
> +			val = readl_relaxed(base + USB_PHY_VBUS_WAKEUP_ID);
> +			val |= VBUS_WAKEUP_WAKEUP_EN;
> +			writel_relaxed(val, base + USB_PHY_VBUS_WAKEUP_ID);
> +
> +			val = readl_relaxed(base + USB_PHY_VBUS_SENSORS);
> +			val |= A_VBUS_VLD_WAKEUP_EN;
> +			writel_relaxed(val, base + USB_PHY_VBUS_SENSORS);
> +		}
> +	}
> +
>  	return utmip_pad_power_off(phy);
>  }
>  
> @@ -765,6 +828,15 @@ static int ulpi_phy_power_off(struct tegra_usb_phy *phy)
>  	usleep_range(5000, 6000);
>  	clk_disable_unprepare(phy->clk);
>  
> +	/*
> +	 * Wakeup currently unimplemented for ULPI, thus PHY needs to be
> +	 * force-resumed.
> +	 */
> +	if (WARN_ON_ONCE(phy->wakeup_enabled)) {
> +		ulpi_phy_power_on(phy);
> +		return -EOPNOTSUPP;
> +	}

How do we control phy->wakeup_enabled? Is this something that we can set
in device tree, for example? I hope so, because otherwise this would
cause a nasty splat every time we try to power-off a ULPI PHY.

Thierry

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