Messages in this thread | | | Date | Fri, 18 Nov 2022 14:30:23 +0100 | From | neil.armstrong@linaro ... | Subject | Re: [PATCH 1/2] dt-bindings: reserved-memory: document Qualcomm MPSS DSM memory |
| |
On 18/11/2022 11:45, Krzysztof Kozlowski wrote: > On 17/11/2022 10:47, Neil Armstrong wrote: >>> >>>> + >>>> +properties: >>>> + compatible: >>>> + const: qcom,mpss-dsm-mem >>> >>> Why do we need dedicated binding and compatible for it instead of using >>> memory-region phandle in the device? >> >> So like rmtfs, this memory zone is shared between APPS and the MPSS subsystem. >> >> Like rmtfs it makes no sense to link it to the MPSS PAS, since it's only a launcher, >> it doesn't represent the MPSS subsystem. > > This also does not represent a device. Memory region is not a device, so > this is as well not correct representation of hardware.
I never used the term device so far, but a shared memory region with a platform specific process to share the region between subsystems.
> >> >> In the PAS startup process, the resources are released from APPS once the MPSS subsystem >> is running, which is not the case with the MPSS DSM where it must be shared during the whole >> lifetime of the system. > > I don't think that PAS releases the region. I checked the > qcom_q6v5_pas.c and there is only ioremap. The device stays loaded thus > the memory stays mapped. Yes PAS does release the firmware region when the firmware is started, qcom_scm_pas_metadata_release() does that.
> > We have already three of such "memory region devices" and we keep > growing it. It's not scalable.
If we want to properly describe this, we must then represent the MPSS subsystem and associate this memory region.
> > Best regards, > Krzysztof
Thanks, Neil
>
| |