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

[Oleksii Moisieiev <Oleksii_Moisieiev@xxxxxxxx>]

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