On 24/01/2024 10:27, Manivannan Sadhasivam wrote: > On Wed, Jan 24, 2024 at 10:01:05AM +0100, Krzysztof Kozlowski wrote: >> On 24/01/2024 09:53, Manivannan Sadhasivam wrote: >>> On Wed, Jan 24, 2024 at 09:45:05AM +0100, Krzysztof Kozlowski wrote: >>>> On 24/01/2024 09:39, Manivannan Sadhasivam wrote: >>>>> On Wed, Jan 24, 2024 at 09:02:16AM +0100, Krzysztof Kozlowski wrote: >>>>>> On 23/01/2024 17:12, Manivannan Sadhasivam wrote: >>>>>>> On Thu, Dec 14, 2023 at 07:18:25AM -0800, Nikunj Kela wrote: >>>>>>>> >>>>>>>> On 12/13/2023 11:49 PM, Krzysztof Kozlowski wrote: >>>>>>>>> On 14/12/2023 07:17, Manivannan Sadhasivam wrote: >>>>>>>>>> On Tue, Dec 12, 2023 at 11:06:42AM -0800, Nikunj Kela wrote: >>>>>>>>>>> + Linaro team >>>>>>>>>>> >>>>>>>>>>> On 12/12/2023 11:01 AM, Krzysztof Kozlowski wrote: >>>>>>>>>>>> On 12/12/2023 18:45, Nikunj Kela wrote: >>>>>>>>>>>>> We are abstracting some resources(ex. clocks) under new firmware on an >>>>>>>>>>>>> existing platform therefore need to make changes in certain drivers to >>>>>>>>>>>>> work with that firmware. We need to make a distinction between two >>>>>>>>>>>>> different variants of the FW. In one case, some resources will be >>>>>>>>>>>>> abstracted while in other case, they won't be abstracted. My query is - >>>>>>>>>>>>> "should we define a new compatible string for the variant with >>>>>>>>>>>>> abstracted resources(in FW) or we should add a new DT property keeping >>>>>>>>>>>>> the compatible same?" >>>>>>>>>>>> Hi, >>>>>>>>>>>> >>>>>>>>>>>> Usually change in the interface or behavior warrants new compatible. >>>>>>>>>>>> Property would be suitable if the same device, e.g. same SoC component >>>>>>>>>>>> with same FW, was configured differently on different boards. >>>>>>>>>>>> >>>>>>>>>> Here, the hardware is going to be the same, but the resources (clocks, >>>>>>>>>> regulators, etc...) will be controlled by the firmware instead of OS. >>>>>>>>> Yeah, that's the problem with generic questions, instead of specific... >>>>>>>>> "Talk is cheap." >>>>>>>>> >>>>>>>>> OK, so the hardware is exactly the same? Does FW bring any >>>>>>>>> incompatibilities in the interface or is it just about the clocks? I >>>>>>>>> guess I should not have included "with same FW" in my last statement. >>>>>>>>> It's true, but way too narrow. Therefore let me rephrase it: >>>>>>>> >>>>>>>> HW is exactly the same. Let me give more insight on the setup. We have been >>>>>>>> using the HW in virtual environment but now the ownership of certain >>>>>>>> resources (e.g. clock controller etc.) is handed over to a different VM(non >>>>>>>> Linux VM). Earlier the ownership of the resources was local to the same >>>>>>>> VM(Linux VM) via passthrough mode so it could directly access them however >>>>>>>> now Linux VM talks to non-Linux VM for its operations for resources that it >>>>>>>> doesn't own anymore via some interface(shared memory/doorbell). So shall we >>>>>>>> use property like 'qcom, controlled-remotely' or do we need a new compatible >>>>>>>> for such setup? >>>>>>>> >>>>>>> >>>>>>> Krzysztof, just a ping on this thread. >>>>>>> >>>>>>> To summarise, the hardware is exactly same. We can consider the case of UFS. The >>>>>>> UFS controller is exactly same in this proposed setup but the resources of the >>>>>>> UFS controller are taken care by the VM. So instead of enabling the resources >>>>>>> one by one, Linux kernel will just ask the VM to do so using an SCMI command. >>>>>>> >>>>>>> Due to this difference, we need to make the changes in the UFS controller >>>>>>> driver. So we want to know if we can use a different compatible for the UFS >>>>>>> controller altogether in DT (this will allow Linux kernel to have a separate >>>>>>> driver and will simplify things) or just use a property like >>>>>>> "remotely-controlled" to let the driver detect this setup and take action >>>>>>> accordingly. >>>>>> >>>>>> What devices do we talk about? Are they released? For which other >>>>>> devices you want to use it? >>>>> >>>>> If you are referring to "peripherals" as "devices", then this new interface is >>>>> going to be applicable to most of the peripherals in the SoC like PCIe, UFS, USB >>>>> etc... >>>>> >>>> >>>> And what about SoCs and final products? >>>> >>> >>> Sorry, I don't understand what you mean. This interface is still under >>> development and going to be available in future SoCs. At that time, we need >>> changes to the drivers to adapt to this interface. >> >> Hm, confused... The message was saying: the same hardware. Same hardware >> means for example Qualcomm SM8550 SoC. >> > > Same hardware means all the peripherals are same as of previous gen SoCs apart > from usual improvements. Maybe I confused you by saying that this interface is > only applicable for newer SoCs, that is not accurate. > > So for instance, even if you take SM8550, Qcom can use this interface (VM) and > ship it to a customer. The VM is just part of the bootloader package. So if the > VM is shipped with an SoC, then Linux should not try to handle resources for the > peripherals and instead request VM to do so using the SCMI interface. Much like > how ACPI behaves in the x86 world. But how the OS should be made aware of the > presence of VM is the question here. Qcom likes to convey that information using > DT. So this is not an existing SoC? Then why do you need to change the meaning of compatible? You have new compatible. > >> OK, I think we are way past possible theoretical discussions. Please >> send patches and we will discuss it from there. >> > > Well, this decision (whether to use a different compatible or a property) > impacts all the peripheral teams inside Qcom as the driver update heavily > depends on this decision. So let's try to conclude the decision here itself. > If something is not clear, please say as you said above. I'll try my best to > clarify. Then again - list exact existing SoCs which will be affected. If this is for future SoCs, then why we are even discussing this? Everything started - first sentence! - with: "existing platform" Sorry guys, I am getting more and more confused. Best regards, Krzysztof
