linux-kernel - Re: kexec on rk3399

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Message-ID: <0408cb6c-1b16-eacb-d47e-17f4ff89e2b8@arm.com>
Date:   Wed, 14 Aug 2019 14:12:26 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Vicente Bergas <vicencb@...il.com>, Felipe Balbi <balbi@...nel.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Will Deacon <will.deacon@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Matthias Brugger <mbrugger@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: kexec on rk3399

On 14/08/2019 13:53, Vicente Bergas wrote:
> On Monday, July 22, 2019 4:31:27 PM CEST, Vicente Bergas wrote:
>> Hi, i have been running linux on rk3399 booted with kexec fine until 5.2
>> From 5.2 onwards, there are memory corruption issues as reported here:
>> http://lkml.iu.edu/hypermail/linux/kernel/1906.2/07211.html
>> kexec has been identified as the principal reason for the issues.
>>
>> It turns out that kexec has never worked reliably on this platform,
>> i was just lucky until recently.
>>
>> Please, can you provide some directions on how to debug the issue?
> 
> Thank you all for your suggestions on where the issue could be.
> 
> It seems that it was the USB driver.
> Now using v5.2.8 booted with kexec from v5.2.8 with a workaround and
> so far so good. It is being tested on the Sapphire board.
> 
> The workaround is:
> --- a/drivers/usb/dwc3/dwc3-of-simple.c
> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
> @@ -133,6 +133,13 @@
>      return 0;
> }
> 
> +static void dwc3_of_simple_shutdown(struct platform_device *pdev)
> +{
> +    struct dwc3_of_simple *simple = platform_get_drvdata(pdev);
> +
> +    reset_control_assert(simple->resets);
> +}
> +
> static int __maybe_unused dwc3_of_simple_runtime_suspend(struct device 
> *dev)
> {
>      struct dwc3_of_simple    *simple = dev_get_drvdata(dev);
> @@ -190,6 +197,7 @@
> static struct platform_driver dwc3_of_simple_driver = {
>      .probe        = dwc3_of_simple_probe,
>      .remove        = dwc3_of_simple_remove,
> +    .shutdown    = dwc3_of_simple_shutdown,
>      .driver        = {
>          .name    = "dwc3-of-simple",
>          .of_match_table = of_dwc3_simple_match,
> 
> If this patch is OK after review i can resubmit it as a pull request.
> Should a similar change be applied to drivers/usb/dwc3/core.c ?

This particular change looks like it's implicitly specific to RK3399, 
which wouldn't be ideal. Presumably if the core dwc3 driver implemented 
shutdown correctly (echoing parts of dwc3_remove(), I guess) then the 
glue layers shouldn't need anything special anyway.

Robin.