On 02.09.2024 13:47, Biju Das wrote: > Hi Claudiu, > >> -----Original Message----- >> From: claudiu beznea <claudiu.beznea@xxxxxxxxx> >> Sent: Monday, September 2, 2024 11:41 AM >> Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC >> >> >> >> On 02.09.2024 12:18, Biju Das wrote: >>>>>>> Do you have any plan to control this power transitions(ALL_ON to AWO and vice versa) in linux? >>>>>> As you know, the RZ/G3S USB PM code is already prepared. This is >>>>>> also configuring these signals when going to suspend/exiting from resume. >>>>>> W/o configuring properly these signals the USB is not working after a suspend/resume cycle. >>>>> One option is to handle SYSC USB PWRRDY signal in TF-A, if you plan >>>>> to handle system transitions >>>> there?? >>>> >>>> As I mentioned, the settings in these registers may be changed by intermediary booting >> applications. >>>> Depending on that, Linux need to control it also on probe for USB to >>>> work (it should be the same with PCIe, these signals seems similar from HW manual description). >>> You mean system transition settings will be override by U-boot, so Linux needs to restore it back?? >> >> It was talking about booting... > > I am also referring to boot. Boot starts with TF-A and it has a system state. > >> >> You proposed to handle SYSC signals from TF-A in a discussion about system power transitions: >> >> "One option is to handle SYSC USB PWRRDY signal in TF-A, if you plan to handle system transitions" >> >> (I was guessing the "system transition" statement there refers to power states transitions, ALL_ON <-> >> AWO/VBAT) > > That is correct. > >> >> and I gave the booting process as a counter example: if we handle it in TF-A it may not be enough as >> these signals might be changed by intermediary booting applications (e.g., U-Boot). > > Why should U-boot override, system state signals such as USB PWRREADY? Can you please give an example. I didn't say *should* but *might* and I was referring to a hypothetical situation where any used application (bootloader) might trigger this signal for whatever reason. My point was to let Linux to handle all the settings that it can do for a particular functionality. The resisters in SYSC address space controlling these signals are accessible to normal world compared to others in the SYSC address spaces. > >> >> To conclude, there are 3 scenarios I see where these signals need to be >> handled: >> 1/ booting >> 2/ suspend to RAM >> 3/ driver unbind/bind > > --> It should be OK as linux is not handling USB PWRREADY signal. > >> >> In case of booting: if we have TF-A to set signals there might be intermediary booting applications >> (e.g. U-Boot) that set these signals also. If it leaves it in improper state and Linux wants to use >> USB then the USB will not work (if Linux doesn't handle it). > > That is the problem of U-boot. U-boot should not override system state signals such as USB PWRREADY. U-Boot can also use USB as well. > >> >> In case of suspend to RAM: as TF-A is the only application in the suspend to RAM chain, it should work >> handling it in TF-A. > > That is correct, TF-A should handle based on system state. > >> >> In case of unbind/bind: currently we don't know if these signals introduces any kind of power saving >> so asserting/de-asserting them in Linux may be useful from this perspective, if any. > > These are system signals, according to me should not be used in unbind/bind. It can be done whatever way. I would just prefer to work for all scenarios. Thank you, Claudiu Beznea > > I may be wrong. > > Cheers, > Biju
