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

[Krzysztof Kozlowski <krzk@kernel.org>]

On Mon, Jun 29, 2020 at 10:54:27AM +0200, Marek Szyprowski wrote:
> Hi Krzysztof,
> 
> On 22.06.2020 19:19, Krzysztof Kozlowski wrote:
> > On Wed, Jun 17, 2020 at 05:26:58PM +0100, Lukasz Luba wrote:
> >> 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.
> 
> Because otherwise the Peach boards hangs during the cpuidle. I didn't 
> analyze the code that much to judge if it is really necessary in all 
> cases, I only restored what worked initially. I can add a comment about 
> that to the commit log if needed.

Yes, please mention this in commit msg.

Best regards,
Krzysztof