linux-kernel - Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260

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Date:   Fri, 26 Oct 2018 11:05:30 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <jonas@...ital-systems.com>
CC:     <alexander.stein@...tec-electronic.com>,
        <linux-kernel@...r.kernel.org>, <sre@...nel.org>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <linux-pm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] power: reset: at91-reset: enable I-cache for
 at91sam9260_reset



On 19.10.2018 13:30, Jonas Danielsson wrote:
> On Wed, Oct 17, 2018 at 3:10 PM <Claudiu.Beznea@...rochip.com> wrote:
>>
>>>
>>> We take the normal path of sys_reboot => kernel_restart => machine_restart ...
>>>
>>> I added code to print the c1 register in different paths. And I-cache
>>> is enabled.
>>> So now I am really confused about why the patch worked.
>>
>> Just saying... maybe your instructions add some delay on the execution path
>> and this is why it helps... try to access cp15 co-processor for read and
>> write back the value you read without actually to modify it, to see if this
>> could be the reason: e.g.:
>>
>> mrc     p15, 0, r0, c1, c0, 0
>> orr     r1, r1, #4096           // whatever is in r1, doesn't matter
>> mcr     p15, 0, r0, c1, c0, 0
>>
> 
> Yes, this also seems to work. I have over 100 reboots completed with this code.
> So what could be the issue here? It seem related to the powering down
> of the sdram at least.

I don't know what could be the issue here. 

> 
> This thread on the AT91SAM community deals with the same issue:
> http://www.at91.com/viewtopic.php?t=25830
> There the solution people chose was removing the SDRAM powering down.
> But that leaves one open to the cause of the errata.
> 
> Do you have any thought on how to approach this?

For now, no. I didn't dug this issue.

Thank you,
Claudiu

> 
>> Thank you,
>> Claudiu Beznea
>>
> 
> Regards
> Jonas
> 
> 
>>>
>>>> Best regards,
>>>> Alexander
>>>
>>> Jonas
>>>
>>>>
>>>>
>>>>
>>>
>>>
> 
> 
>