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

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Date:   Fri, 19 Oct 2018 12:30:05 +0200
From:   Jonas Danielsson <jonas@...ital-systems.com>
To:     Claudiu.Beznea@...rochip.com
Cc:     alexander.stein@...tec-electronic.com,
        linux-kernel@...r.kernel.org, Sebastian Reichel <sre@...nel.org>,
        Nicolas Ferre <Nicolas.Ferre@...rochip.com>,
        Alexandre Belloni <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 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.

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?

> Thank you,
> Claudiu Beznea
>

Regards
Jonas

> >
> >> Best regards,
> >> Alexander
> >
> > Jonas
> >
> >>
> >>
> >>
> >
> >

-- 

JONAS DANIELSSON
Software Developer

+46 72 361 5022
Malmö - Sweden

ORBITAL SYSTEMS
orbital-systems.com

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