Re: [RFC PATCH v5 02/10] xen/arm: scmi-smc: update to be used under sci subsystem

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 22 Jul 2025, Oleksii Moisieiev wrote:
> From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
> 
> The introduced SCI (System Control Interface) subsystem provides unified
> interface to integrate in Xen SCI drivers which adds support for ARM
> firmware (EL3, SCP) based software interfaces (like SCMI) that are used in
> system management. The SCI subsystem allows to add drivers for different FW
> interfaces or have different drivers for the same FW interface (for example,
> SCMI with different transports).
> 
> This patch updates SCMI over SMC calls handling layer, introduced by
> commit 3e322bef8bc0 ("xen/arm: firmware: Add SCMI over SMC calls handling
> layer"), to be SCI driver:
> - convert to DT device;
> - convert to SCI Xen interface.
> 
> There are no functional changes in general, the driver is just adopted
> to the SCI interface.
> 
> Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
> Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@xxxxxxxx>
> ---
> 
> 
> 
>  xen/arch/arm/firmware/Kconfig                | 13 ++-
>  xen/arch/arm/firmware/scmi-smc.c             | 93 +++++++++++---------
>  xen/arch/arm/include/asm/firmware/scmi-smc.h | 41 ---------
>  xen/arch/arm/vsmc.c                          |  5 +-
>  xen/include/public/arch-arm.h                |  1 +
>  5 files changed, 64 insertions(+), 89 deletions(-)
>  delete mode 100644 xen/arch/arm/include/asm/firmware/scmi-smc.h
> 
> diff --git a/xen/arch/arm/firmware/Kconfig b/xen/arch/arm/firmware/Kconfig
> index fc7918c7fc..bbf88fbb9a 100644
> --- a/xen/arch/arm/firmware/Kconfig
> +++ b/xen/arch/arm/firmware/Kconfig
> @@ -8,9 +8,18 @@ config ARM_SCI
>  
>  menu "Firmware Drivers"
>  
> +choice
> +     prompt "ARM SCI driver type"
> +     default SCMI_SMC
> +     help
> +     Choose which ARM SCI driver to enable.
> +
> +config ARM_SCI_NONE
> +     bool "none"
> +
>  config SCMI_SMC
>       bool "Forward SCMI over SMC calls from hwdom to EL3 firmware"
> -     default y
> +     select ARM_SCI
>       help
>         This option enables basic awareness for SCMI calls using SMC as
>         doorbell mechanism and Shared Memory for transport ("arm,scmi-smc"
> @@ -18,4 +27,6 @@ config SCMI_SMC
>         firmware node is used to trap and forward corresponding SCMI SMCs
>         to firmware running at EL3, for calls coming from the hardware domain.
>  
> +endchoice
> +
>  endmenu
> diff --git a/xen/arch/arm/firmware/scmi-smc.c 
> b/xen/arch/arm/firmware/scmi-smc.c
> index 33473c04b1..13d1137592 100644
> --- a/xen/arch/arm/firmware/scmi-smc.c
> +++ b/xen/arch/arm/firmware/scmi-smc.c
> @@ -9,6 +9,7 @@
>   * Copyright 2024 NXP
>   */
>  
> +#include <asm/device.h>
>  #include <xen/acpi.h>
>  #include <xen/device_tree.h>
>  #include <xen/errno.h>
> @@ -16,12 +17,11 @@
>  #include <xen/sched.h>
>  #include <xen/types.h>
>  
> +#include <asm/firmware/sci.h>
>  #include <asm/smccc.h>
> -#include <asm/firmware/scmi-smc.h>
>  
>  #define SCMI_SMC_ID_PROP   "arm,smc-id"
>  
> -static bool __ro_after_init scmi_enabled;
>  static uint32_t __ro_after_init scmi_smc_id;
>  
>  /*
> @@ -41,14 +41,11 @@ static bool scmi_is_valid_smc_id(uint32_t fid)
>   *
>   * Returns true if SMC was handled (regardless of response), false otherwise.
>   */
> -bool scmi_handle_smc(struct cpu_user_regs *regs)
> +static bool scmi_handle_smc(struct cpu_user_regs *regs)
>  {
>      uint32_t fid = (uint32_t)get_user_reg(regs, 0);
>      struct arm_smccc_res res;
>  
> -    if ( !scmi_enabled )
> -        return false;
> -
>      if ( !scmi_is_valid_smc_id(fid) )
>          return false;
>  
> @@ -78,49 +75,45 @@ bool scmi_handle_smc(struct cpu_user_regs *regs)
>      return true;
>  }
>  
> -static int __init scmi_check_smccc_ver(void)
> +static int scmi_smc_domain_init(struct domain *d,
> +                                struct xen_domctl_createdomain *config)
>  {
> -    if ( smccc_ver < ARM_SMCCC_VERSION_1_1 )
> -    {
> -        printk(XENLOG_WARNING
> -               "SCMI: No SMCCC 1.1 support, SCMI calls forwarding 
> disabled\n");
> -        return -ENOSYS;
> -    }
> +    if ( !is_hardware_domain(d) )
> +        return 0;

Should we also check for config->arch.sci_type ==
XEN_DOMCTL_CONFIG_ARM_SCI_SCMI_SMC ?


> +    d->arch.sci_enabled = true;
> +    printk(XENLOG_DEBUG "SCMI: %pd init\n", d);
>      return 0;
>  }