On Fri, 18 Apr 2025 13:28:23 +0200 Quentin Schulz <quentin.sch...@cherry.de> wrote:
Hi Quentin, thanks for having a look! > 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. As Yixun Lan already pointed out, the DT is not available at this point, and doing several pull-ups to get this information from the DT into the SPL image are really over the top for this purpose. This is more a sweet hacker device: I often have devices with eMMC and SPI flash, but without a FEL button. So the idea was to just pick a GPIO and use menuconfig to set it. Then I could just connect this pin to GND during boot, to get into FEL and test-boot firmware. "Connect to GND" could really be a jumper or even the tip of a screwdriver ;-) So I don't think this qualifies to being defined in the DT, really. > You can have the property in the -u-boot.dtsi then if you want? > > 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 Yes, I have a patch to add this particular button as a GPIO button into the DT, so people can use it for whatever they want in Linux (trigger reboot, update, you name it). But this is rather orthogonal to this problem, as mentioned above. > the DT, which aren't strictly speaking hardware definition either :) ). Please don't get me started on this, we don't need to make it worse ;-) Cheers, Andre
