linux-kernel - Re: [PATCH 1/2] PM: base: power: don't try to use non-existing RTC for storing data

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Message-ID: <3f08f433-a228-d512-3608-3ed0c797e653@suse.com>
Date:   Tue, 7 Sep 2021 06:18:23 +0200
From:   Juergen Gross <jgross@...e.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        xen-devel@...ts.xenproject.org,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Stable <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] PM: base: power: don't try to use non-existing RTC
 for storing data

On 06.09.21 19:07, Rafael J. Wysocki wrote:
> On Fri, Sep 3, 2021 at 11:02 AM Juergen Gross <jgross@...e.com> wrote:
>>
>> On 03.09.21 10:56, Greg Kroah-Hartman wrote:
>>> On Fri, Sep 03, 2021 at 10:49:36AM +0200, Juergen Gross wrote:
>>>> In there is no legacy RTC device, don't try to use it for storing trace
>>>> data across suspend/resume.
>>>>
>>>> Cc: <stable@...r.kernel.org>
>>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>>> ---
>>>>    drivers/base/power/trace.c | 10 ++++++++++
>>>>    1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
>>>> index a97f33d0c59f..b7c80849455c 100644
>>>> --- a/drivers/base/power/trace.c
>>>> +++ b/drivers/base/power/trace.c
>>>> @@ -13,6 +13,7 @@
>>>>    #include <linux/export.h>
>>>>    #include <linux/rtc.h>
>>>>    #include <linux/suspend.h>
>>>> +#include <linux/init.h>
>>>>
>>>>    #include <linux/mc146818rtc.h>
>>>>
>>>> @@ -165,6 +166,9 @@ void generate_pm_trace(const void *tracedata, unsigned int user)
>>>>       const char *file = *(const char **)(tracedata + 2);
>>>>       unsigned int user_hash_value, file_hash_value;
>>>>
>>>> +    if (!x86_platform.legacy.rtc)
>>>> +            return 0;
>>>
>>> Why does the driver core code here care about a platform/arch-specific
>>> thing at all?  Did you just break all other arches?
>>
>> This file is only compiled for x86. It depends on CONFIG_PM_TRACE_RTC,
>> which has a "depends on X86" attribute.
> 
> This feature uses the CMOS RTC memory to store data, so if that memory
> is not present, it's better to avoid using it.
> 
> Please feel free to add
> 
> Reviewed-by: Rafael J. Wysocki <rafael@...nel.org>

Thanks!

> 
> to this patch or let me know if you want me to take it.
> 

No, I can take it with the other patch of this small series, thanks.


Juergen

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