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. Cheers, Biju
