Re: [PATCH v2 1/3] usb: dwc3: core: Host wake up support from system suspend

[Matthias Kaehlcke <mka@chromium.org>]

Hi Sandeep,

On Thu, Jul 09, 2020 at 12:40:15AM +0530, Sandeep Maheswaram wrote:
> Avoiding phy powerdown in host mode so that it can be wake up by devices.
> Added need_phy_for_wakeup flag to distinugush resume path and hs_phy_flags
> to check connection status and set phy mode and  configure interrupts.
> 
> Signed-off-by: Sandeep Maheswaram <sanm@codeaurora.org>
> ---
>  drivers/usb/dwc3/core.c | 47 ++++++++++++++++++++++++++++++++++++++++-------
>  drivers/usb/dwc3/core.h |  2 ++
>  2 files changed, 42 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 25c686a7..eb7c225 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -31,12 +31,14 @@
>  #include <linux/usb/gadget.h>
>  #include <linux/usb/of.h>
>  #include <linux/usb/otg.h>
> +#include <linux/usb/hcd.h>
>  
>  #include "core.h"
>  #include "gadget.h"
>  #include "io.h"
>  
>  #include "debug.h"
> +#include "../host/xhci.h"
>  
>  #define DWC3_DEFAULT_AUTOSUSPEND_DELAY	5000 /* ms */
>  
> @@ -1627,10 +1629,36 @@ static int dwc3_core_init_for_resume(struct dwc3 *dwc)
>  	return ret;
>  }
>  
> +static void dwc3_set_phy_speed_flags(struct dwc3 *dwc)
> +{
> +
> +	int i, num_ports;
> +	u32 reg;
> +	struct usb_hcd	*hcd = platform_get_drvdata(dwc->xhci);
> +	struct xhci_hcd	*xhci_hcd = hcd_to_xhci(hcd);
> +
> +	dwc->hs_phy_flags &= ~(PHY_MODE_USB_HOST_HS | PHY_MODE_USB_HOST_LS);

Where is hs_phy_flags initialized? As far as I can tell it isn't, hence when
dwc3_set_phy_speed_flags() is executed the first time it is 0 (from
devm_kzalloc()), and after the '&=' it is still 0. The next time it will have
whatever value it was set to in the below loop, which is then cleared by
the '&='. It seems you could as well just write 'dwc->hs_phy_flags = 0',
which is clearer, unless the field is used in some other way that isn't
obvious to me.

> +
> +	reg = readl(&xhci_hcd->cap_regs->hcs_params1);
> +
> +	num_ports = HCS_MAX_PORTS(reg);
> +	for (i = 0; i < num_ports; i++) {
> +		reg = readl(&xhci_hcd->op_regs->port_status_base + i * 0x04);
> +		if (reg & PORT_PE) {
> +			if (DEV_HIGHSPEED(reg) || DEV_FULLSPEED(reg))
> +				dwc->hs_phy_flags |= PHY_MODE_USB_HOST_HS;
> +			else if (DEV_LOWSPEED(reg))
> +				dwc->hs_phy_flags |= PHY_MODE_USB_HOST_LS;

Is another entry for DEV_SUPERSPEED needed?

> +		}
> +	}
> +	phy_set_mode(dwc->usb2_generic_phy, dwc->hs_phy_flags);
> +}
> +
>  static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  {
>  	unsigned long	flags;
>  	u32 reg;
> +	struct usb_hcd  *hcd = platform_get_drvdata(dwc->xhci);
>  
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
> @@ -1643,9 +1671,12 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  		dwc3_core_exit(dwc);
>  		break;
>  	case DWC3_GCTL_PRTCAP_HOST:
> +		dwc3_set_phy_speed_flags(dwc);
>  		if (!PMSG_IS_AUTO(msg)) {
> -			dwc3_core_exit(dwc);
> -			break;
> +			if (usb_wakeup_enabled_descendants(hcd->self.root_hub))
> +				dwc->need_phy_for_wakeup = true;
> +			else
> +				dwc->need_phy_for_wakeup = false;
>  		}
>  
>  		/* Let controller to suspend HSPHY before PHY driver suspends */
> @@ -1705,11 +1736,13 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  		break;
>  	case DWC3_GCTL_PRTCAP_HOST:
>  		if (!PMSG_IS_AUTO(msg)) {
> -			ret = dwc3_core_init_for_resume(dwc);
> -			if (ret)
> -				return ret;
> -			dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_HOST);
> -			break;
> +			if (!dwc->need_phy_for_wakeup) {
> +				ret = dwc3_core_init_for_resume(dwc);

Before this patch we had the combo dwc3_core_exit() / dwc3_core_init_for_resume(),
now it is only dwc3_core_init_for_resume() for !dwc->need_phy_for_wakeup.
Doesn't this cause trouble with enable counts, e.g. with clk_bulk_prepare_enable()
being called in dwc3_core_init_for_resume(), without the corresponding
clk_bulk_disable_unprepare() calls in dwc3_core_exit()?