On Tuesday 15 December 2015 18:42:36 Thierry Reding wrote: > On Tue, Dec 15, 2015 at 05:34:00PM +0100, Arnd Bergmann wrote: > > On Tuesday 15 December 2015 17:31:22 Thierry Reding wrote: > > > On Mon, Dec 14, 2015 at 12:39:44PM +0100, Arnd Bergmann wrote: > > > > On Wednesday 18 November 2015 17:56:22 Andy Yan wrote: > > > > > rockchip platform have a protocol to pass the kernel reboot > > > > > mode to bootloader by some special registers when system reboot. > > > > > By this way the bootloader can take different action according > > > > > to the different kernel reboot mode, for example, command > > > > > "reboot loader" will reboot the board to rockusb mode, this is > > > > > a very convenient way to get the board enter download mode. > > > > > > > > > > Signed-off-by: Andy Yan <andy.yan@xxxxxxxxxxxxxx> > > > > > > > > Adding John Stultz to Cc > > > > > > > > I just saw this thread pop up again, and had to think of John's recent > > > > patch to unify this across platforms. > > > > > > > > John, can you have a look at this driver too, and see how it fits in? > > > > I think this is yet another variant, using an MMIO register rather than > > > > RAM (as HTC / NVIDIA does) or SRAM (as Qualcomm does), but otherwise > > > > it conceptually fits in with what you had. > > > > > > FWIW, Tegra typically does use an MMIO register as well. See > > > drivers/soc/tegra/pmc.c:tegra_pmc_restart_notify(). I don't know what > > > HTC does, but if it's writing somewhere in RAM it isn't using the > > > standard way of resetting the SoC. There's early boot ROM code which I > > > think evaluates the PMC_SCRATCH0 register on Tegra to determine which > > > mode to boot into. That's before even any firmware gets the chance of > > > doing anything. I just checked the android lollipop tree, and I could not find a pmc_restart_notify function, only this file https://android.googlesource.com/kernel/tegra/+/android-tegra-flounder-3.10-lollipop-release/drivers/htc_debug/stability/reboot_params.c with the device that stores into RAM. It looks like HTC ported over a driver that they were already using on some Qualcomm MSM8960 device, as in https://gitlab.com/MaC/android_kernel_htc_msm8960/blob/859977fc723f59a6b707df1d70e80826ee1dccc4/arch/arm/mach-msm/htc/htc_restart_handler.c On Android marshmallow (Flounder), that file again does not exist, and I don't see how it's done. > > HTC apparently uses a separate RAM area to pass the reboot reason, > > and they have a driver to store that, which is separate from the > > driver that they use for actually rebooting the machine. > > I wasn't very clear, but the PMC_SCRATCH0 register is used to store the > reset reason. It supports the recovery mode, which I think is really an > Android thing, "bootloader" will typically cause the bootloader not to > boot anything, and "forced-recovery" will go into a recovery mode that > is used to bootstrap the device (usually by uploading a "miniloader" > that initializes RAM, downloads a bootloader for booting or flashing an > operating system, ...). > > The write that resets the SoC is to a different register. So is this scratch register interpreted by some maskrom code, or by code that can be provided by the OEM? Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
