linux-kernel - Re: [PATCH] OMAP3 ROM Random Number Generator support

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Message-ID: <20130401165949.GI10155@atomide.com>
Date:	Mon, 1 Apr 2013 09:59:50 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Ивайло Димитров 
	<freemangordon@....bg>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	juha.yrjola@...idboot.com, linux@....linux.org.uk, mpm@...enic.com,
	herbert@...dor.apana.org.au, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] OMAP3 ROM Random Number Generator support

* Ивайло Димитров <freemangordon@....bg> [130331 05:10]:
>  
> Hi Pali,
> 
> Yep, the code looks almost identical, I guess with some tweaks all SMC code from that patch could be removed and instead used the one from SMC PPA API. 
> 
> What I don't get, is why one needs to disable/enable fiqs/irqs:
> 
> +static int call_sec_rom(u32 appl_id, u32 proc_id, u32 flag, ...)
> +{
> +	va_list ap;
> +	u32 ret;
> +	u32 val;
> +
> +	va_start(ap, flag);
> +	val = *(u32 *) &ap;
> +	local_irq_disable();
> +	local_fiq_disable();
> +	ret = omap3_rom_rng_call(appl_id, proc_id, flag,
> +				 (u32) virt_to_phys((void *) val));
> +	local_fiq_enable();
> +	local_irq_enable();
> +	va_end(ap);
> +
> +	return ret;
> +}
> 
> Do you have any idea why is that needed? Any other code I've ever seen to call SM, does not disable fiqs/irqs, is RNG SMC somehow special? I know this is Nokia's code, but still, if we can get some understanding...

Sounds like the fiq handling can be dropped based on what
the TI guys posted recently about FIQs only be available in
the secure mode starting with omap2.

Regards,

Tony
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