linux-kernel - Re: [PATCH v12 4/6] usb: dwc3: qcom: Keep power domain on to retain controller status

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Date:   Thu, 7 Apr 2022 11:01:57 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sandeep Maheswaram <quic_c_sanm@...cinc.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_pkondeti@...cinc.com, quic_ppratap@...cinc.com,
        quic_kriskura@...cinc.com, quic_vpulyala@...cinc.com
Subject: Re: [PATCH v12 4/6] usb: dwc3: qcom: Keep power domain on to retain
 controller status

On Thu, Apr 07, 2022 at 02:15:02PM +0530, Sandeep Maheswaram wrote:
> Keep the power domain on in order to retain controller status and
> to support wakeup from devices.
> 
> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
> ---
>  drivers/usb/dwc3/dwc3-qcom.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index 9804a19..35087cf 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -17,6 +17,7 @@
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/phy/phy.h>
> +#include <linux/pm_domain.h>
>  #include <linux/usb/of.h>
>  #include <linux/reset.h>
>  #include <linux/iopoll.h>
> @@ -724,6 +725,7 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  	struct resource		*res, *parent_res = NULL;
>  	int			ret, i;
>  	bool			ignore_pipe_clk;
> +	struct generic_pm_domain *genpd;
>  
>  	qcom = devm_kzalloc(&pdev->dev, sizeof(*qcom), GFP_KERNEL);
>  	if (!qcom)
> @@ -732,6 +734,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, qcom);
>  	qcom->dev = &pdev->dev;
>  
> +	genpd = pd_to_genpd(qcom->dev->pm_domain);
> +
>  	if (has_acpi_companion(dev)) {
>  		qcom->acpi_pdata = acpi_device_get_match_data(dev);
>  		if (!qcom->acpi_pdata) {
> @@ -839,6 +843,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto interconnect_exit;
>  
> +	genpd->flags |= GENPD_FLAG_ALWAYS_ON;

Not sure it really matters, but could this be done conditionally based
on device_can_wakeup() of the dwc3 core device?

> +
>  	device_init_wakeup(&pdev->dev, 1);

Now that the dwc3 core looks at the wakeup-source property it seems
this driver should enable wakeup only when it is enabled for the
core.

Actually I wonder if it would make sense to leave wakeup for dwc3-qcom
'officially' disabled, and just make all wakeup related decisions
based on the wakeup configuration of the dwc3 core (as
dwc3_qcom_en/disable_interrupts() already do). The separate wakeup
policies for dwc3 core and dwc3-qcom are confusing and don't seem to
add any value.