On Wed, Sep 09, 2020 at 04:10:41PM +0800, JC Kuo wrote:
> This commit implements the complete programming sequence for ELPG
> entry and exit.
> 
>  1. At ELPG entry, invokes tegra_xusb_padctl_enable_phy_sleepwalk()
>     and tegra_xusb_padctl_enable_phy_wake() to configure XUSB PADCTL
>     sleepwalk and wake detection circuits to maintain USB lines level
>     and respond to wake events (wake-on-connect, wake-on-disconnect,
>     device-initiated-wake).
> 
>  2. At ELPG exit, invokes tegra_xusb_padctl_disable_phy_sleepwalk()
>     and tegra_xusb_padctl_disable_phy_wake() to disarm sleepwalk and
>     wake detection circuits.
> 
> At runtime suspend, XUSB host controller can enter ELPG to reduce
> power consumption. When XUSB PADCTL wake detection circuit detects
> a wake event, an interrupt will be raised. xhci-tegra driver then
> will invoke pm_runtime_resume() for xhci-tegra.
> 
> Runtime resume could also be triggered by protocol drivers, this is
> the host-initiated-wake event. At runtime resume, xhci-tegra driver
> brings XUSB host controller out of ELPG to handle the wake events.
> 
> The same ELPG enter/exit procedure will be performed for system
> suspend/resume path so USB devices can remain connected across SC7.
> 
> Signed-off-by: JC Kuo <jckuo@nvidia.com>
> ---
> v3:
>    use 'unsigned int' for PHY index
>    remove unnecessary 'else'
>    drop IRQF_TRIGGER_HIGH when invokes devm_request_threaded_irq()
>    
>  drivers/usb/host/xhci-tegra.c | 389 +++++++++++++++++++++++++++++++---
>  1 file changed, 360 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
> index aabff8ee0bb3..ba3f40e78171 100644
> --- a/drivers/usb/host/xhci-tegra.c
> +++ b/drivers/usb/host/xhci-tegra.c
> @@ -15,9 +15,11 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
> +#include <linux/of_irq.h>
>  #include <linux/phy/phy.h>
>  #include <linux/phy/tegra/xusb.h>
>  #include <linux/platform_device.h>
> +#include <linux/usb/ch9.h>
>  #include <linux/pm.h>
>  #include <linux/pm_domain.h>
>  #include <linux/pm_runtime.h>
> @@ -224,6 +226,7 @@ struct tegra_xusb {
>  
>  	int xhci_irq;
>  	int mbox_irq;
> +	int padctl_irq;
>  
>  	void __iomem *ipfs_base;
>  	void __iomem *fpci_base;
> @@ -269,10 +272,13 @@ struct tegra_xusb {
>  		dma_addr_t phys;
>  	} fw;
>  
> +	bool suspended;
>  	struct tegra_xusb_context context;
>  };
>  
>  static struct hc_driver __read_mostly tegra_xhci_hc_driver;
> +static int tegra_xusb_exit_elpg(struct tegra_xusb *tegra, bool runtime);
> +static int tegra_xusb_enter_elpg(struct tegra_xusb *tegra, bool runtime);

Can we reshuffle the code to avoid these predeclarations? Looks like
they're only used in tegra_xusb_runtime_{suspend,resume}(), so perhaps
move the implementations right before those?

Thierry