Re: [PATCH] firmware: psci: handle unsupported SET_SUSPEND_MODE in PC mode

[Patrick DELAUNAY <patrick.delaunay@foss.st.com>]

Hi,

On 10/30/26 09:32, Sudeep Holla wrote:
> On Thu, Oct 29, 2026 at 07:16:25PM +0100, Patrick Delaunay wrote:
>> The PSCI specification makes PSCI_SET_SUSPEND_MODE optional. If it
>> returns NOT_SUPPORTED when Linux requests platform-coordinated (PC)
>> mode, Linux can assume that PC mode is in effect. Treat this response
>> as success so PSCI power-domain providers can initialize when firmware
>> does not support OS-initiated (OSI) mode.
>>
>> Continue to report an error when OSI mode is requested but
>> SET_SUSPEND_MODE is not supported.
>>
> So, your platform advertises the presence/support for OSI mode and yet
> opted for not implementing SET_SUSPEND_MODE ? If so, it is indeed a
> firmware bug as reported.
>

I think it is no realy a platform bug but a too strict management in 
Linux kernel,

for PSCI power domain.


The OSI mode is not yet supported by the STM32MP25 platform in Linux at

upstream but I introduce PSCI domains in device tree (but without idle power

domain) just to prepare this activation in next steps.


As the PSCI support is not activated in Firmware (TF-A BL31), the 
firmware correctly

expose its capacities (PSCI_OS_INIT_MODE =0)

=> PSCI feature indicate that OSI is not supported 
(FF_SUPPORTS_OS_INIT_MODE = 0)

=> PSCI_SET_SUSPEND_MODE function is not supported (optional when OSI is 
not supported)


in Linux side, the power domain driver 
(drivers/cpuidle/cpuidle-psci-domain.c)

correctly check the support of OSI:

     bool use_osi = psci_has_osi_support();


in STM32MP25 platform use_osi = false, so the driver request

Plafrom Cooordinated mode (PC mode) as expected

But here  the GENPD driver try to use optional function to set mode:


     /* let's try to enable OSI. */
     ret = psci_set_osi_mode(use_osi);
     if (ret)
         goto remove_pd;


And the problem occurs here because the optional function is called but 
the normal use case

is not handled (OSI mode not supported / PSCI_SET_SUSPEND_MODE not 
supported)


With the proposed patch, the Linux kernel can have PSCI domain in device 
tree even when

PSCI OSI support is deactivated in PSCI firmware (or not yet activated): 
the domain are

always ON (GENPD_FLAG_ALWAYS_ON)


NB: I hesitate between the current patch and a patch in PSCI power 
domain driver:


     /* let's try to enable OSI. */
     ret = psci_set_osi_mode(use_osi);

+ if (ret == -EOPNOTSUPP && !use_osi)

+    ret = 0;

     if (ret)
         goto remove_pd;


but I patch PSCI firmware driver because I think it is a more generic 
place to handle optional PSCI function.


Regards


Patrick