Re: [PATCH] usb: dwc3: qcom: Add shutdown callback for dwc3

From: Felipe Balbi <balbi@kernel.org>
To: Sandeep Maheswaram <sanm@codeaurora.org>,
	Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Stephen Boyd <swboyd@chromium.org>,
	Doug Anderson <dianders@chromium.org>,
	Matthias Kaehlcke <mka@chromium.org>
Cc: linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	Manu Gautam <mgautam@codeaurora.org>,
	Sandeep Maheswaram <sanm@codeaurora.org>
Subject: Re: [PATCH] usb: dwc3: qcom: Add shutdown callback for dwc3
Date: Wed, 13 Jan 2021 10:40:01 +0200	[thread overview]
Message-ID: <87sg7544da.fsf@kernel.org> (raw)
In-Reply-To: <1605162619-10064-1-git-send-email-sanm@codeaurora.org>

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Hi,

Sandeep Maheswaram <sanm@codeaurora.org> writes:
> This patch adds a shutdown callback to USB DWC QCOM driver to ensure that
> it is properly shutdown in reboot/shutdown path. This is required
> where SMMU address translation is enabled like on SC7180
> SoC and few others. If the hardware is still accessing memory after
> SMMU translation is disabled as part of SMMU shutdown callback in
> system reboot or shutdown path, then IOVAs(I/O virtual address)
> which it was using will go on the bus as the physical addresses which
> might result in unknown crashes (NoC/interconnect errors).
>
> Signed-off-by: Sandeep Maheswaram <sanm@codeaurora.org>

sounds like this is fixing a bug. Do you have a Fixes tag for it? Should
this go to stable?

> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index c703d55..a930e06 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -790,13 +790,11 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  	return ret;
>  }
>  
> -static int dwc3_qcom_remove(struct platform_device *pdev)
> +static void __dwc3_qcom_teardown(struct dwc3_qcom *qcom)
>  {
> -	struct dwc3_qcom *qcom = platform_get_drvdata(pdev);
> -	struct device *dev = &pdev->dev;
>  	int i;
>  
> -	of_platform_depopulate(dev);
> +	of_platform_depopulate(qcom->dev);
>  
>  	for (i = qcom->num_clocks - 1; i >= 0; i--) {
>  		clk_disable_unprepare(qcom->clks[i]);
> @@ -807,12 +805,27 @@ static int dwc3_qcom_remove(struct platform_device *pdev)
>  	dwc3_qcom_interconnect_exit(qcom);
>  	reset_control_assert(qcom->resets);
>  
> -	pm_runtime_allow(dev);
> -	pm_runtime_disable(dev);
> +	pm_runtime_allow(qcom->dev);
> +	pm_runtime_disable(qcom->dev);
> +}

you can make the changes smaller by adding:

	struct device *dev = qcom->dev;

The nothing else needs to change in this function ;-)

-- 
balbi

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