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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 27 Aug 2025, Oleksii Moisieiev wrote:
> On 23/08/2025 03:26, Stefano Stabellini wrote:
> > 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 ?
> >
> Current changes assume that only SCMI_SMC is present. This check was 
> added in the subsequent patch when multiagent was introduced.

In theory ARM_SCI_NONE is possible?