linux-kernel - Re: [PATCH 1/3] firmware/psci: Fix cpu_resume entry points with THUMB2

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Date:   Fri, 28 Sep 2018 14:47:05 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@...linux.org.uk>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Brian Norris <computersforpeace@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Rob Herring <robh@...nel.org>, Doug Berger <opendmb@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] firmware/psci: Fix cpu_resume entry points with
 THUMB2_KERNEL

On Thu, Sep 27, 2018 at 12:27:09PM -0700, Florian Fainelli wrote:
> When THUMB2_KERNEL is enabled, we would be failing to resume from an
> idle or system suspend call where the reentry point is set to
> cpu_resume() because that function is in Thumb2. Utilize
> cpu_resume_arm() for ARM 32-bit kernels which takes care of the mode
> switching for us.

Looking at the PSCI spec, if bit[0] of the entry point address is set,
the CPU should be placed into thumb state.

So either there's a FW bug here, or perhaps we're stripping bit[0] when
we do the __pa_symbol() dance.

Which firmware have you seen this with?

Thanks,
Mark.

> Fixes: 8b6f2499ac45 ("ARM: 8511/1: ARM64: kernel: PSCI: move PSCI idle management code to drivers/firmware")
> Fixes: faf7ec4a92c0 ("drivers: firmware: psci: add system suspend support")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/firmware/psci.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index c80ec1d03274..f8b154384483 100644
> --- a/drivers/firmware/psci.c
> +++ b/drivers/firmware/psci.c
> @@ -400,9 +400,14 @@ int psci_cpu_init_idle(unsigned int cpu)
>  static int psci_suspend_finisher(unsigned long index)
>  {
>  	u32 *state = __this_cpu_read(psci_power_state);
> +	unsigned long reentry;
>  
> -	return psci_ops.cpu_suspend(state[index - 1],
> -				    __pa_symbol(cpu_resume));
> +#ifdef CONFIG_ARM
> +	reentry = __pa_symbol(cpu_resume_arm);
> +#else
> +	reentry = __pa_symbol(cpu_resume);
> +#endif
> +	return psci_ops.cpu_suspend(state[index - 1], reentry);
>  }
>  
>  int psci_cpu_suspend_enter(unsigned long index)
> @@ -437,8 +442,15 @@ CPUIDLE_METHOD_OF_DECLARE(psci, "psci", &psci_cpuidle_ops);
>  
>  static int psci_system_suspend(unsigned long unused)
>  {
> +	unsigned long reentry;
> +
> +#ifdef CONFIG_ARM
> +	reentry = __pa_symbol(cpu_resume_arm);
> +#else
> +	reentry = __pa_symbol(cpu_resume);
> +#endif
>  	return invoke_psci_fn(PSCI_FN_NATIVE(1_0, SYSTEM_SUSPEND),
> -			      __pa_symbol(cpu_resume), 0, 0);
> +			      reentry, 0, 0);
>  }
>  
>  static int psci_system_suspend_enter(suspend_state_t state)
> -- 
> 2.17.1
>