From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Tue, 15 Dec 2015 17:34 +0100
Subject: [PATCH v3 3/5] soc: rockchip: add reboot notifier driver
In-Reply-To: <20151215163120.GA24031@ulmo.nvidia.com>
References: <1447840044-19689-1-git-send-email-andy.yan@rock-chips.com>
 <10162108.nOThMrrbdf@wuerfel> <20151215163120.GA24031@ulmo.nvidia.com>
Message-ID: <3759218.6sItdW65UG@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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@rock-chips.com>
> > 
> > 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.

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.

	Arnd