Re: [PATCH v2 13/16] firmware/psci: Expose SMCCC version through psci_ops

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Christoffer Dall <christoffer.dall@linaro.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jon Masters <jcm@redhat.com>
Subject: Re: [PATCH v2 13/16] firmware/psci: Expose SMCCC version through psci_ops
Date: Mon, 29 Jan 2018 18:39:33 +0000	[thread overview]
Message-ID: <20180129183933.GB24577@e107981-ln.cambridge.arm.com> (raw)
In-Reply-To: <20180129174559.1866-14-marc.zyngier@arm.com>

On Mon, Jan 29, 2018 at 05:45:56PM +0000, Marc Zyngier wrote:
> Since PSCI 1.0 allows the SMCCC version to be (indirectly) probed,
> let's do that at boot time, and expose the version of the calling
> convention as part of the psci_ops structure.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  drivers/firmware/psci.c | 21 +++++++++++++++++++++
>  include/linux/psci.h    |  6 ++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index e9493da2b111..dd035aaa1c33 100644
> --- a/drivers/firmware/psci.c
> +++ b/drivers/firmware/psci.c
> @@ -511,6 +511,26 @@ static void __init psci_init_migrate(void)
>  	pr_info("Trusted OS resident on physical CPU 0x%lx\n", cpuid);
>  }
>  
> +static void __init psci_init_smccc(u32 ver)
> +{
> +	int feature = PSCI_RET_NOT_SUPPORTED;
> +
> +	if (PSCI_VERSION_MAJOR(ver) >= 1)
> +		feature = psci_features(ARM_SMCCC_VERSION_FUNC_ID);
> +
> +	if (feature == PSCI_RET_NOT_SUPPORTED) {
> +		psci_ops.variant = SMCCC_VARIANT_1_0;
> +	} else {
> +		ver = invoke_psci_fn(ARM_SMCCC_VERSION_FUNC_ID, 0, 0, 0);
> +		if (ver != ARM_SMCCC_VERSION_1_1)
> +			psci_ops.variant = SMCCC_VARIANT_1_0;
> +		else
> +			psci_ops.variant = SMCCC_VARIANT_1_1;
> +	}
> +
> +	pr_info("SMC Calling Convention v1.%d\n", psci_ops.variant);
> +}
> +
>  static void __init psci_0_2_set_functions(void)
>  {
>  	pr_info("Using standard PSCI v0.2 function IDs\n");
> @@ -557,6 +577,7 @@ static int __init psci_probe(void)
>  	psci_0_2_set_functions();
>  
>  	psci_init_migrate();
> +	psci_init_smccc(ver);

Given that SMCCC_VARIANT_1_0 is already the default value (unless you do
the same we did with the conduit) we can move psci_init_smccc() call
inside the if below (that is there to detect a callable psci_features())
and remove the check in psci_init_smccc(), up to you.

>  
>  	if (PSCI_VERSION_MAJOR(ver) >= 1) {
>  		psci_init_cpu_suspend();
> diff --git a/include/linux/psci.h b/include/linux/psci.h
> index f2679e5faa4f..83fd16a37be3 100644
> --- a/include/linux/psci.h
> +++ b/include/linux/psci.h
> @@ -31,6 +31,11 @@ enum psci_conduit {
>  	PSCI_CONDUIT_HVC,
>  };
>  
> +enum smccc_variant {
> +	SMCCC_VARIANT_1_0,
> +	SMCCC_VARIANT_1_1,
> +};
> +
>  struct psci_operations {
>  	u32 (*get_version)(void);
>  	int (*cpu_suspend)(u32 state, unsigned long entry_point);
> @@ -41,6 +46,7 @@ struct psci_operations {
>  			unsigned long lowest_affinity_level);
>  	int (*migrate_info_type)(void);
>  	enum psci_conduit conduit;
> +	enum smccc_variant variant;

Nit: I would add an smccc_ prefix to the variant field (or rename it
to smccc_version).

You can add my:

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>