Re: [PATCH 1/4] ARM: exynos: Apply little core workaround only under secure firmware

[Krzysztof Kozlowski <krzk@kernel.org>]

On Wed, Jun 17, 2020 at 05:26:58PM +0100, Lukasz Luba wrote:
> Hi Marek,
> 
> I've give it a try with hotplug torture tests and has only one a minor
> comment.
> 
> On 6/16/20 9:12 AM, Marek Szyprowski wrote:
> > The additional soft-reset call during little core power up was needed
> > to properly boot all cores on the Exynos5422-based boards with secure
> > firmware (like Odroid XU3/XU4 family). This however broke big.LITTLE
> > CPUidle driver, which worked only on boards without secure firmware
> > (like Peach-Pit/Pi Chromebooks).
> > 
> > Apply the workaround only when board is running under secure firmware.
> > 
> > Fixes: 833b 5794 e330 ("ARM: EXYNOS: reset Little cores when cpu is up")

Fix the Fixes tag (in case of resend, otherwise I'll do it).

> > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > ---
> >   arch/arm/mach-exynos/mcpm-exynos.c | 10 +++++++---
> >   1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
> > index 9a681b421ae1..cd861c57d5ad 100644
> > --- a/arch/arm/mach-exynos/mcpm-exynos.c
> > +++ b/arch/arm/mach-exynos/mcpm-exynos.c
> > @@ -26,6 +26,7 @@
> >   #define EXYNOS5420_USE_L2_COMMON_UP_STATE	BIT(30)
> >   static void __iomem *ns_sram_base_addr __ro_after_init;
> > +static bool secure_firmware __ro_after_init;
> >   /*
> >    * The common v7_exit_coherency_flush API could not be used because of the
> > @@ -58,15 +59,16 @@ static void __iomem *ns_sram_base_addr __ro_after_init;
> >   static int exynos_cpu_powerup(unsigned int cpu, unsigned int cluster)
> >   {
> >   	unsigned int cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
> > +	bool state;
> >   	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
> >   	if (cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
> >   		cluster >= EXYNOS5420_NR_CLUSTERS)
> >   		return -EINVAL;
> > -	if (!exynos_cpu_power_state(cpunr)) {
> > -		exynos_cpu_power_up(cpunr);
> > -
> > +	state = exynos_cpu_power_state(cpunr);
> > +	exynos_cpu_power_up(cpunr);
> 
> I can see that you have moved this call up, probably to avoid more
> 'if-else' stuff. I just wanted to notify you that this function
> 'exynos_cpu_powerup' is called twice when cpu is going up:
> 1. by the already running cpu i.e. CPU0 and the 'state' is 0 for i.e.
> CPU2
> 2. by the newly starting cpu i.e. CPU2 by running
> 'secondary_start_kernel' and the state is 3.
> 
> In this scenario the 'exynos_cpu_power_up' will be called twice.
> I have checked in hotplug that this is not causing any issues, but
> thought maybe it's worth share it with you. Maybe you can double check
> in TRM that this is not causing anything.

This brings the old code, before 833b5794e33. I wonder why? I understood
that only soft-reset should be skipped.

Best regards,
Krzysztof