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SubjectRe: [PATCH v1 01/24] psci: Accessor for configured PSCI version
On 2020-11-09 11:32, David Brazdil wrote:
> The version of PSCI that the kernel should use to communicate with
> firmware is typically obtained from probing PSCI_VERSION. However, that
> doesn't work for PSCI v0.1 where the host gets the information from
> DT/ACPI, or if PSCI is not supported / was disabled.
>
> KVM's host PSCI proxy needs to be configured with the same version
> used by the host driver. Expose the PSCI version used by the host
> with a read-only accessor.
>
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
> drivers/firmware/psci/psci.c | 11 +++++++++++
> include/linux/psci.h | 8 ++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/drivers/firmware/psci/psci.c
> b/drivers/firmware/psci/psci.c
> index 00af99b6f97c..bc1b2d60fdbf 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -49,6 +49,13 @@ static int resident_cpu = -1;
> struct psci_operations psci_ops;
> static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
>
> +static int driver_version = PSCI_VERSION(0, 0);
> +
> +int psci_driver_version(void)
> +{
> + return driver_version;
> +}
> +
> bool psci_tos_resident_on(int cpu)
> {
> return cpu == resident_cpu;
> @@ -461,6 +468,8 @@ static int __init psci_probe(void)
> return -EINVAL;
> }
>
> + driver_version = ver;
> +
> psci_0_2_set_functions();
>
> psci_init_migrate();
> @@ -514,6 +523,8 @@ static int __init psci_0_1_init(struct device_node
> *np)
>
> pr_info("Using PSCI v0.1 Function IDs from DT\n");
>
> + driver_version = PSCI_VERSION(0, 1);
> +
> if (!of_property_read_u32(np, "cpu_suspend", &id)) {
> psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
> psci_ops.cpu_suspend = psci_cpu_suspend;
> diff --git a/include/linux/psci.h b/include/linux/psci.h
> index 2a1bfb890e58..5b5dcf176aa6 100644
> --- a/include/linux/psci.h
> +++ b/include/linux/psci.h
> @@ -21,6 +21,14 @@ bool psci_power_state_is_valid(u32 state);
> int psci_set_osi_mode(bool enable);
> bool psci_has_osi_support(void);
>
> +/**
> + * The version of the PSCI specification followed by the driver.
> + * This is equivalent to calling PSCI_VERSION except:
> + * (a) it also works for PSCI v0.1, which does not support
> PSCI_VERSION, and
> + * (b) it is set to v0.0 if the PSCI driver was not initialized.
> + */
> +int psci_driver_version(void);
> +
> struct psci_operations {
> u32 (*get_version)(void);
> int (*cpu_suspend)(u32 state, unsigned long entry_point);

I still maintain that populating .get_version in all cases instead of
duplicating an existing functionality is a better outcome. PSCI not
supported would be implied by .get_version being NULL.

What breaks?

M.
--
Jazz is not dead. It just smells funny...

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