linux-kernel - Re: [PATCH v8 1/2] usb: dwc3: qcom: Add interconnect support in dwc3 driver

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Message-ID: <20200709172636.GL3191083@google.com>
Date:   Thu, 9 Jul 2020 10:26:36 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sandeep Maheswaram <sanm@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Manu Gautam <mgautam@...eaurora.org>,
        Chandana Kishori Chiluveru <cchiluve@...eaurora.org>
Subject: Re: [PATCH v8 1/2] usb: dwc3: qcom: Add interconnect support in dwc3
 driver

Hi,

inline one more thing I forgot to comment on in my previous mail

On Thu, Jul 09, 2020 at 09:30:11PM +0530, Sandeep Maheswaram wrote:
> Add interconnect support in dwc3-qcom driver to vote for bus
> bandwidth.
> 
> This requires for two different paths - from USB master to
> DDR slave. The other is from APPS master to USB slave.
> 
> Signed-off-by: Sandeep Maheswaram <sanm@...eaurora.org>
> Signed-off-by: Chandana Kishori Chiluveru <cchiluve@...eaurora.org>
> Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
> ---
>  drivers/usb/dwc3/dwc3-qcom.c | 127 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 125 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index 1dfd024..5532988 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
>
> ...
>
> @@ -648,6 +763,11 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  		goto depopulate;
>  	}
>  
> +	qcom->max_speed = usb_get_maximum_speed(&qcom->dwc3->dev);

What if the function returns USB_SPEED_UNKNOWN?

You need a reasonable default value for that case, which I think would be
USB_SPEED_SUPER (i.e. the controller would work properly at super speed,
though the interconnects would consume a bit more power than necessary lower
speed modes).