linux-kernel - Re: [PATCH 5/8] power: reset: at91-reset: use at91_ramc

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Message-ID: <20141022071845.GM10616@piout.net>
Date:	Wed, 22 Oct 2014 09:18:45 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-kernel@...r.kernel.org,
	David Woodhouse <dwmw2@...radead.org>,
	linux-arm-kernel@...ts.infradead.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 5/8] power: reset: at91-reset: use at91_ramc_shutdown

On 22/10/2014 at 09:08:10 +0200, Thomas Petazzoni wrote :
> Dear Alexandre Belloni,
> 
> On Tue, 21 Oct 2014 23:55:37 +0200, Alexandre Belloni wrote:
> 
> >  /*
> >  * unless the SDRAM is cleanly shutdown before we hit the
> >  * reset register it can be left driving the data bus and
> >  * killing the chance of a subsequent boot from NAND
> >  */
> > -static void at91sam9260_restart(enum reboot_mode mode, const char *cmd)
> > +static void at91_restart(enum reboot_mode mode, const char *cmd)
> >  {
> > -	asm volatile(
> > -		/* Align to cache lines */
> > -		".balign 32\n\t"
> > -
> > -		/* Disable SDRAM accesses */
> > -		"str	%2, [%0, #" __stringify(AT91_SDRAMC_TR) "]\n\t"
> > -
> > -		/* Power down SDRAM */
> > -		"str	%3, [%0, #" __stringify(AT91_SDRAMC_LPR) "]\n\t"
> > +	if (at91_ramc_shutdown)
> > +		at91_ramc_shutdown();
> >  
> > +	asm volatile(
> >  		/* Reset CPU */
> > -		"str	%4, [%1, #" __stringify(AT91_RSTC_CR) "]\n\t"
> > +		"str	%1, [%0, #" __stringify(AT91_RSTC_CR) "]\n\t"
> >  
> >  		"b	.\n\t"
> 
> Are you sure this is working properly? There was a reason to have the
> SDRAM controller shutdown right before resetting the CPU: the code was
> ensuring that all those assembly instructions fitted in one cache line,
> so that even if the SDRAM controller gets shutdown, the rest of the
> code can properly execute until resetting the CPU. Now, the SDRAM
> controller shutdown code and the code resetting the CPU are in
> completely separate places, which break this assumption.
> 

It it still working properly, I believe it is still fitting the cache
line.

> And also, you forgot to Cc: Maxime Ripard who did the initial work on
> this at91-reset controller.
> 

Yeah, I realized after sending the patches.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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