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

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Date:   Mon, 18 Jan 2021 12:02:01 +0530
From:   sanm@...eaurora.org
To:     Felipe Balbi <balbi@...nel.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>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...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>
Subject: Re: [PATCH] usb: dwc3: qcom: Add shutdown callback for dwc3

On 2021-01-13 14:10, Felipe Balbi wrote:
> Hi,
> 
> Sandeep Maheswaram <sanm@...eaurora.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@...eaurora.org>
> 
> sounds like this is fixing a bug. Do you have a Fixes tag for it? 
> Should
> this go to stable?
> 
Didn't encounter any bug till now but made this change to prevent issue.

>> 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 ;-)

I will do this in next version