From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v3 3/5] soc: rockchip: add reboot notifier driver Date: Tue, 15 Dec 2015 21:38:41 +0100 Message-ID: <15127971.1juVbocOjP@wuerfel> References: <1447840044-19689-1-git-send-email-andy.yan@rock-chips.com> <3759218.6sItdW65UG@wuerfel> <20151215174234.GB24031@ulmo.nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151215174234.GB24031-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-rockchip" Errors-To: linux-rockchip-bounces+glpar-linux-rockchip=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Thierry Reding Cc: mark.rutland-5wv7dgnIgG8@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, khilman-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org, heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org, pawel.moll-5wv7dgnIgG8@public.gmane.org, ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org, sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, Andy Yan , wxt-TNX95d0MmH7DzftRWevZcw@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, benchan-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org List-Id: devicetree@vger.kernel.org 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 > > > > > > > > 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