Hi Claudiu, > -----Original Message----- > From: Biju Das > Sent: Monday, September 2, 2024 11:48 AM > Subject: RE: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC > > 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. > > > > > 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. > > > > > 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. > > I may be wrong. Just to add the below are the 4 system states (power mode) for this LSI. If I understand correctly, we need to configure USB PWRRDY signal only when there is a transition from ALL_ON to AWO mode and vice versa. as you see on AWO mode only CM-33 is active. • ALL_OFF mode: All CPUs and peripheral modules can not be worked. • ALL_ON mode: All CPUs and peripheral modules can be worked. • AWO mode: Cortex-M33 and peripheral modules in PD_VCC and PD_VBATT domain can be worked. • VBATT mode: Only RTC, tamper detection and backup registers can be worked. System manager which is controlling both CA-55 and CM-33, will set USB PWRRDY signal based on system state. Since we don't have system manager for controlling both CA-55 and CM-33 Probably from CA-55 perspective, TF-A should be sufficient. During boot clr USB PWR READY signal in TF-A. STR case, suspend set USB PWR READY signal in TF-A. STR case, resume clr USB PWR READY signal in TF-A. I am not expert in this area. I may be wrong. Maybe we need to get an opinion from Power experts in Linux. Cheers, Biju
