Re: [PATCH v2 1/4] dt-bindings: power: reset: add document for reboot-mode driver

[Andy Yan]

Hi Rob:
   thanks for your review.
On 2016å01æ21æ 02:28, Rob Herring wrote:
> On Tue, Jan 12, 2016 at 07:29:49PM +0800, Andy Yan wrote:
> > add device tree binding document for reboot-mode driver
> >
> > Signed-off-by: Andy Yan <andy.yan@xxxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v2: None
> > Changes in v1: None
> >
> >   .../bindings/power/reset/reboot-mode.txt           | 41 +++++++++++++++++
> >   .../bindings/power/reset/syscon-reboot-mode.txt    | 52 ++++++++++++++++++++++
> >   2 files changed, 93 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/power/reset/reboot-mode.txt
> >   create mode 100644 Documentation/devicetree/bindings/power/reset/syscon-reboot-mode.txt
> >
> > diff --git a/Documentation/devicetree/bindings/power/reset/reboot-mode.txt b/Documentation/devicetree/bindings/power/reset/reboot-mode.txt
> > new file mode 100644
> > index 0000000..81d9f66
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/power/reset/reboot-mode.txt
> > @@ -0,0 +1,41 @@
> > +Generic reboot mode core map driver
> > +
> > +This driver get reboot mode arguments and call the write
> > +interface to stores the magic value in special register
> > +or ram . Then the bootloader can read it and take different
> > +action according to the argument stored.
> > +
> > +Required properties:
> > +- compatible: only support "syscon-reboot-mode" now.
> > +
> > +Each mode is represented as a sub-node of reboot_mode:
> > +
> > +Subnode required properties:
> > +- linux,mode: reboot mode command,such as "loader", "recovery", "fastboot".
> > +- loader,magic: magic number for the mode, this is vendor specific.
> > +
> > +Example:
> > +	reboot_mode {
> reboot-mode instead please.

    Sorry, I have already correct it in DT file, forget it here. It 
will be changed in next version.

> > +		compatible = "syscon-reboot-mode";
> > +		offset = <0x40>;
> This doc by itself is a little confusing. For example, is a child of the
> syscon node? I would remove offset (and perhaps compatible) from this
> example.

   Yes, is a child of a syscon mapped node. For example, Rockchip 
platform use a register of PMU(rk3066/rk3288) or GRF(rk3036), PMU and 
GRF are aleady mapped by syscon.
   offset and compatible are used by write interface driver like 
syscon-reboot-mode.c. If you don't like it appear in the core map doc, I 
will move it to the syscon-reboot-mode.txt?
> > +
> > +		loader {
> > +			linux,mode = "loader";
> > +			loader,magic = <BOOT_LOADER>;
> > +		};
> Sorry, my previous suggestion was not clear. I'm suggesting get rid of
> the subnodes and just do properties like this:
>
> loader = <BOOT_LOADER>;
> maskrom = <BOOT_MASKROM>;
>
> That's the same amount of information unless node names and linux,mode
> values are going to diverge. Do they need to? I can't see a reason.

    Because the command"linux,mode" and value"loader,magic" is vendor 
specific. I don't know what commands and how many mode other platform 
will use. So as John says in his reply, this sort of flexibility help us 
adapt the driver to different hardware/system environments.
> We need to be clear what loader means. More specifically, it is boot
> into bootloader shell.
    Actually, Rockchip platform will reboot into a bootloader download 
mode with this command. This mode can download faster than maskrom 
download mode.
> > +
> > +		maskrom {
> In theory, the bootrom could have multiple modes. This typically means a
> USB download mode. So perhaps a more precise name would be
> "rom-download".
>
> In chips I'm familiar with the bootrom mode is selected via a different
> mechanism than the secondary bootloader modes, but I suppose the same
> mechanism could be used.
   Yes , they use the same mechanism.
> > +			linux,mode = "maskrom";
> > +			loader,magic = <BOOT_MASKROM>;
> > +		};
> > +
> > +		recovery {
> > +			linux,mode = "recovery";
> > +			loader,magic = <BOOT_RECOVERY>;
> > +		};
> > +
> > +		fastboot {
> > +			linux,mode = "fastboot";
> > +			loader,magic = <BOOT_FASTBOOT>;
> > +		};