linux-kernel - Re: [PATCH v2 7/7] ARM: EXYNOS: cpuidle: add secure firmware support to AFTR mode code

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Message-id: <2929163.ygQuOcYWlC@amdc1032>
Date:	Mon, 02 Jun 2014 15:40:21 +0200
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	Kukjin Kim <kgene.kim@...sung.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH v2 7/7] ARM: EXYNOS: cpuidle: add secure firmware support
 to AFTR mode code

On Monday, June 02, 2014 03:15:07 PM Tomasz Figa wrote:
> Hi,
> 
> On 02.06.2014 14:35, Bartlomiej Zolnierkiewicz wrote:
> > * Use do_idle firmware method instead of cpu_do_idle() on boards with
> >   secure firmware enabled.
> > 
> > * Use sysram_ns_base_addr + 0x24 address for exynos_boot_vector_addr()
> >   and sysram_ns_base_addr + 0x20 one for exynos_boot_vector_flag() on
> >   boards with secure firmware enabled.
> > 
> > This patch fixes hang on an attempt to enter AFTR mode for TRATS2
> > board (which uses EXYNOS4412 SoC with secure firmware enabled).
> > 
> > This patch shouldn't cause any functionality changes on boards that
> > don't use secure firmware.
> > 
> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> > Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> > ---
> >  arch/arm/mach-exynos/pm.c        | 8 ++++++--
> >  drivers/cpuidle/cpuidle-exynos.c | 7 ++++++-
> >  2 files changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm/mach-exynos/pm.c b/arch/arm/mach-exynos/pm.c
> > index 0fb9a5a..62a0a5e 100644
> > --- a/arch/arm/mach-exynos/pm.c
> > +++ b/arch/arm/mach-exynos/pm.c
> > @@ -169,7 +169,9 @@ int exynos_cluster_power_state(int cluster)
> >  
> >  static inline void __iomem *exynos_boot_vector_addr(void)
> >  {
> > -	if (samsung_rev() == EXYNOS4210_REV_1_1)
> > +	if (firmware_run())
> > +		return sysram_ns_base_addr + 0x24;
> > +	else if (samsung_rev() == EXYNOS4210_REV_1_1)
> 
> Aha, so this is the use case for the function added by patch 1/7.
> 
> Well, I don't see the need to do it this way and complicate the API. As
> I mentioned in my comments to patches 2/7 and 5/7, more general firmware
> operations should be taking care of setting those registers to
> appropriate values and so there shouldn't be any need to use them
> directly outside the implementation of firmware ops.

More general firmware operations would handle the secure firmware case
fine but how would you like to handle a fallback case given that you
cannot use samsung_rev() etc. in drivers/cpuidle/cpuidle-exynos.c?

> [snip]
> 
> >  static int idle_finisher(unsigned long flags)
> >  {
> >  	exynos_enter_aftr();
> > -	cpu_do_idle();
> > +	if (firmware_run())
> > +		/* no need to check the return value on EXYNOS SoCs */
> > +		call_firmware_op(do_idle, FW_DO_IDLE_AFTR);
> > +	else
> > +		cpu_do_idle();
> 
> This could be done just by
> 
> 	if (call_firmware_op(do_idle, FW_DO_IDLE_AFTR) == -ENOSYS)
> 		cpu_do_idle();
> 
> which is 3 lines less than with a function that is suppose to simplify
> the code.

OK.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

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