linux-kernel - Re: [PATCH v3 7/8] usb: dwc3: qcom: Start USB in 'host mode' on the SDM845

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Date:   Wed, 12 Jun 2019 06:57:36 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     alokc@...eaurora.org, andy.gross@...aro.org,
        david.brown@...aro.org, wsa+renesas@...g-engineering.com,
        linus.walleij@...aro.org, balbi@...nel.org,
        gregkh@...uxfoundation.org, ard.biesheuvel@...aro.org,
        jlhugo@...il.com, linux-i2c@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/8] usb: dwc3: qcom: Start USB in 'host mode' on the
 SDM845

On Tue, 11 Jun 2019, Bjorn Andersson wrote:

> On Mon 10 Jun 01:42 PDT 2019, Lee Jones wrote:
> 
> > When booting with Device Tree, the current default boot configuration
> > table option, the request to boot via 'host mode' comes from the
> > 'dr_mode' property.
> 
> As I said in my previous review, the default mode for SDM845 is OTG. For
> the MTP specifically we specify the default mode to be peripheral (was
> host).
> 
> 
> The remaining thing that worries me with this patch is that I do expect
> that at least one of the USB-C ports is OTG. But I am not able to
> conclude anything regarding this and host-only is a good default for
> this type of device, so I suggest that we merge this.

Right.  So one thing to consider is that Qualcomm Mobile Dept. do not
use ACPI for Linux, so this patch-set only affects the Laptop
form factor devices, where 'host' is the expected mode.

> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Thanks for taking the time to review this Bjorn.

Hopefully we can get Felipe's attention soon.

Felipe,

One thing to think about when taking Bjorn's Reviewed-by into
consideration; although we both work for Linaro, we actually operate
in different teams.  Bjorn is on the Qualcomm Landing Team, and as an
ex-Qualcomm employee he is in an excellent position to review these
patches, thus his Review should carry more weight than the usual
co-worker review IMHO.

TIA.

> > A property of the same name can be used inside
> > ACPI tables too.  However it is missing from the SDM845's ACPI tables
> > so we have to supply this information using Platform Device Properties
> > instead.
> > 
> > This does not change the behaviour of any currently supported devices.
> > The property is only set on ACPI enabled platforms, thus for H/W
> > booting DT, unless a 'dr_mode' property is present, the default is
> > still OTG (On-The-Go) as per [0].  Any new ACPI devices added will
> > also be able to over-ride this implementation by providing a 'dr_mode'
> > property in their ACPI tables.  In cases where 'dr_mode' is omitted
> > from the tables AND 'host mode' should not be the default (very
> > unlikely), then we will have to add some way of choosing between them
> > at run time - most likely by ACPI HID.
> > 
> > [0] Documentation/devicetree/bindings/usb/generic.txt
> > 
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  drivers/usb/dwc3/dwc3-qcom.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> > index 1e1f12b7991d..55ba04254e38 100644
> > --- a/drivers/usb/dwc3/dwc3-qcom.c
> > +++ b/drivers/usb/dwc3/dwc3-qcom.c
> > @@ -444,6 +444,11 @@ static int dwc3_qcom_clk_init(struct dwc3_qcom *qcom, int count)
> >  	return 0;
> >  }
> >  
> > +static const struct property_entry dwc3_qcom_acpi_properties[] = {
> > +	PROPERTY_ENTRY_STRING("dr_mode", "host"),
> > +	{}
> > +};
> > +
> >  static int dwc3_qcom_acpi_register_core(struct platform_device *pdev)
> >  {
> >  	struct dwc3_qcom 	*qcom = platform_get_drvdata(pdev);
> > @@ -488,6 +493,13 @@ static int dwc3_qcom_acpi_register_core(struct platform_device *pdev)
> >  		goto out;
> >  	}
> >  
> > +	ret = platform_device_add_properties(qcom->dwc3,
> > +					     dwc3_qcom_acpi_properties);
> > +	if (ret < 0) {
> > +		dev_err(&pdev->dev, "failed to add properties\n");
> > +		goto out;
> > +	}
> > +
> >  	ret = platform_device_add(qcom->dwc3);
> >  	if (ret)
> >  		dev_err(&pdev->dev, "failed to add device\n");

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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