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

Andy Yan
2016-01-21T06:27:57Z

Hi Rob:
thanks for your review.
On 2016?01?21? 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@rock-chips.com>
>>
>> ---
>>
>> 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>;
>> + };
>
>
>