Hi On 13:28 Fri 18 Apr , Quentin Schulz wrote: > Hi Andre, > > On 4/17/25 2:05 AM, Andre Przywara wrote: > > Some boards with Allwinner SoCs feature a "FEL" key, sometimes also > > labelled "uboot", which triggers the BootROM FEL mode, when pressed upon > > power-on or reset. This allows to access the SoC's memory via USB OTG, > > and to upload and execute code. There is a tool to upload our U-Boot image > > and immediately boot it, when the SoC is in FEL mode. > > > > To mimic this convenient behaviour on boards without such a dedicated key, > > we can query a GPIO pin very early in the SPL boot, then trigger the > > BootROM FEL routine. There has not been much of a SoC or board setup at > > this point, so we enter the BROM in a rather pristine state still. On > > 64-bit SoCs the required AArch32 reset guarantees a clean CPU state anyway. > > > > Any GPIO can be used for that, the signal is expected to be active low, > > consequently we enable the pull-up resistors for that pin. A board (or a > > user) is expected to specify the GPIO name using the > > CONFIG_SUNXI_FAKE_FEL_PIN Kconfig variable. When this variable is not set, > > the compiler will optimise away the call. > > > > Call the code first thing in board_init_f(), which is the first sunxi > > specific C routine. > > > > Signed-off-by: Andre Przywara <andre.przyw...@arm.com> > > --- > > arch/arm/mach-sunxi/Kconfig | 10 ++++++++++ > > arch/arm/mach-sunxi/board.c | 31 +++++++++++++++++++++++++++++++ > > 2 files changed, 41 insertions(+) > > > > diff --git a/arch/arm/mach-sunxi/Kconfig b/arch/arm/mach-sunxi/Kconfig > > index ab432390d3c..f1cfdb548bc 100644 > > --- a/arch/arm/mach-sunxi/Kconfig > > +++ b/arch/arm/mach-sunxi/Kconfig > > @@ -825,6 +825,16 @@ config USB3_VBUS_PIN > > ---help--- > > See USB1_VBUS_PIN help text. > > > > +config SUNXI_FAKE_FEL_PIN > > + string "fake FEL GPIO pin" > > + default "" > > + ---help--- > > + Define a GPIO that shall force entering FEL mode when a button > > + connected to this pin is pressed at boot time. This must be an > > + active low signal, the internal pull-up resistors are activated. > > + This takes a string in the format understood by sunxi_name_to_gpio, > > + e.g. PH1 for pin 1 of port H. > > + > > Why not use the DT for that? Then you wouldn't even need to assume the > polarity of the signal or whether pull-up/downs need to be activated, etc. > > You can have the property in the -u-boot.dtsi then if you want? > I've raised similar question in v1, but it's in SPL which has no DT available see Andre's commment https://lore.kernel.org/all/20250409110126.2cc59...@donnerap.manchester.arm.com/
maybe better add a SPL prefix to config? or some info in help docs to state clearly it should only work in SPL phase? > While the FEL button on the X96 is "fake", it does what it says, just in > software, maybe that is close enough to "hardware definition" which > would make it suitable for the DT (well, we also store binman nodes in > the DT, which aren't strictly speaking hardware definition either :) ). > > Cheers, > Quentin -- Yixun Lan (dlan)
