linux-kernel - Re: [PATCH 4/6] usb: cdns3: support power-off of controller when in host role

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Message-ID: <20231114083838.GC64573@nchen-desktop>
Date:   Tue, 14 Nov 2023 16:38:38 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Théo Lebrun <theo.lebrun@...tlin.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Roger Quadros <rogerq@...nel.org>,
        Pawel Laszczak <pawell@...ence.com>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/6] usb: cdns3: support power-off of controller when in
 host role

On 23-11-13 15:26:59, Théo Lebrun wrote:
> The controller is not being reconfigured at resume. Change resume to
> redo hardware config if quirk CDNS3_RESET_ON_RESUME is active.

Current logic has power off judgement, see cdns3_controller_resume for
detail.

> 
> Platform data comes from the parent driver (eg cdns3-ti).
> 
> The quirk should be passed if the platform driver knows that the
> controller might be in reset state at resume. We do NOT reconfigure the
> hardware without this quirk to avoid losing state if we did a suspend
> without reset.
> 
> If the quirk is on, we notify the xHCI subsystem that:
> 
> 1. We reset on resume. It will therefore redo the xHC init & trigger
>    such message as "root hub lost power or was reset" in dmesg.
> 
> 2. It should disable/enable clocks on suspend/resume. This does not
>    matter on our platform as xhci-plat does not get access to any clock
>    but it would be the right thing to do if we indeed had such clocks.
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> ---
>  drivers/usb/cdns3/core.h |  1 +
>  drivers/usb/cdns3/host.c | 20 ++++++++++++++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/usb/cdns3/core.h b/drivers/usb/cdns3/core.h
> index 81a9c9d6be08..7487067ba23f 100644
> --- a/drivers/usb/cdns3/core.h
> +++ b/drivers/usb/cdns3/core.h
> @@ -44,6 +44,7 @@ struct cdns3_platform_data {
>  			bool suspend, bool wakeup);
>  	unsigned long quirks;
>  #define CDNS3_DEFAULT_PM_RUNTIME_ALLOW	BIT(0)
> +#define CDNS3_RESET_ON_RESUME		BIT(1)
>  };
>  
>  /**
> diff --git a/drivers/usb/cdns3/host.c b/drivers/usb/cdns3/host.c
> index 6164fc4c96a4..a81019a7c8cc 100644
> --- a/drivers/usb/cdns3/host.c
> +++ b/drivers/usb/cdns3/host.c
> @@ -88,6 +88,9 @@ static int __cdns_host_init(struct cdns *cdns)
>  		goto err1;
>  	}
>  
> +	if (cdns->pdata && cdns->pdata->quirks & CDNS3_RESET_ON_RESUME)
> +		cdns->xhci_plat_data->quirks |= XHCI_RESET_ON_RESUME | XHCI_SUSPEND_RESUME_CLKS;
> +

If you set this flag, how could you support the USB remote wakeup
request? In that case, the USB bus does not expect re-enumeration.

>  	if (cdns->pdata && (cdns->pdata->quirks & CDNS3_DEFAULT_PM_RUNTIME_ALLOW))
>  		cdns->xhci_plat_data->quirks |= XHCI_DEFAULT_PM_RUNTIME_ALLOW;
>  
> @@ -124,6 +127,18 @@ static void cdns_host_exit(struct cdns *cdns)
>  	cdns_drd_host_off(cdns);
>  }
>  
> +static int cdns_host_suspend(struct cdns *cdns, bool do_wakeup)
> +{
> +	if (!do_wakeup)
> +		cdns_drd_host_off(cdns);
> +	return 0;
> +}
> +
> +static int cdns_host_resume(struct cdns *cdns, bool hibernated)
> +{
> +	return cdns_drd_host_on(cdns);

This one will redo if controller's power is off, please consider both
on and power situation.

> +}
> +
>  int cdns_host_init(struct cdns *cdns)
>  {
>  	struct cdns_role_driver *rdrv;
> @@ -137,6 +152,11 @@ int cdns_host_init(struct cdns *cdns)
>  	rdrv->state	= CDNS_ROLE_STATE_INACTIVE;
>  	rdrv->name	= "host";
>  
> +	if (cdns->pdata && cdns->pdata->quirks & CDNS3_RESET_ON_RESUME) {
> +		rdrv->suspend = cdns_host_suspend;
> +		rdrv->resume = cdns_host_resume;
> +	}
> +
>  	cdns->roles[USB_ROLE_HOST] = rdrv;
>  
>  	return 0;
> 
> -- 
> 2.41.0
> 

-- 

Thanks,
Peter Chen