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    SubjectRe: [PATCH v2 1/3] power: reset: read priority from device tree
    On 2014-12-01 18:42, Guenter Roeck wrote:
    > On Mon, Dec 01, 2014 at 09:38:09AM -0800, Feng Kan wrote:
    >> On Mon, Dec 1, 2014 at 9:29 AM, Stefan Agner <stefan@agner.ch> wrote:
    >> > On 2014-12-01 18:15, Feng Kan wrote:
    >> >> On Mon, Dec 1, 2014 at 9:03 AM, Stefan Agner <stefan@agner.ch> wrote:
    >> >>> This patch adds an optional property which allows to specify the
    >> >>> reset source priority. This priority is used by the kernel restart
    >> >>> handler call chain to sort out the proper reset/restart method.
    >> >>> Depending on the power design of a board or other machine/board
    >> >>> specific peculiarity, it is not possible to pick a generic priority.
    >> >>>
    >> >>> Signed-off-by: Stefan Agner <stefan@agner.ch>
    >> >>> ---
    >> >>> Documentation/devicetree/bindings/power/reset/syscon-reboot.txt | 3 +++
    >> >>> drivers/power/reset/syscon-reboot.c | 5 ++++-
    >> >>> 2 files changed, 7 insertions(+), 1 deletion(-)
    >> >>>
    >> >>> diff --git a/Documentation/devicetree/bindings/power/reset/syscon-reboot.txt b/Documentation/devicetree/bindings/power/reset/syscon-reboot.txt
    >> >>> index 1190631..ee41d9c 100644
    >> >>> --- a/Documentation/devicetree/bindings/power/reset/syscon-reboot.txt
    >> >>> +++ b/Documentation/devicetree/bindings/power/reset/syscon-reboot.txt
    >> >>> @@ -11,6 +11,9 @@ Required properties:
    >> >>> - offset: offset in the register map for the reboot register (in bytes)
    >> >>> - mask: the reset value written to the reboot register (32 bit access)
    >> >>>
    >> >>> +Optional properties:
    >> >>> +- priority: define the priority of the reset (0-255, defaults to 128)
    >> >>> +
    >> >>> Default will be little endian mode, 32 bit access only.
    >> >>>
    >> >>> Examples:
    >> >>> diff --git a/drivers/power/reset/syscon-reboot.c b/drivers/power/reset/syscon-reboot.c
    >> >>> index 815b901..3060d6b 100644
    >> >>> --- a/drivers/power/reset/syscon-reboot.c
    >> >>> +++ b/drivers/power/reset/syscon-reboot.c
    >> >>> @@ -67,8 +67,11 @@ static int syscon_reboot_probe(struct platform_device *pdev)
    >> >>> if (of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask))
    >> >>> return -EINVAL;
    >> >>>
    >> >>> - ctx->restart_handler.notifier_call = syscon_restart_handle;
    >> >>> ctx->restart_handler.priority = 128;
    >> >>> + of_property_read_u32(pdev->dev.of_node, "priority",
    >> >>> + &ctx->restart_handler.priority);
    >> >>
    >> >> What is this for?
    >> >
    >> > What do you mean? The moved line "ctx->restart_handler.notifier_call =
    >> > syscon_restart_handle;"? When one reads the diff, it looks like that
    >> > line was moved, in fact I tried to keep the of_property_read function
    >> > calls together. But I had to move the assignation of the default
    >> > priority in front of restart_handler.priority. That's what is the
    >> > outcome...
    >>
    >> I believe Guenter explained above already. Actually this help to solve one of
    >> my problem. Thanks.
    >
    > Since Mark doesn't seem to be happy with the idea of making the priority
    > dt-configurable, the alternative might be to just set a higher priority for
    > syscon triggered resets, as suggested by Stefan. Not as flexible, but it
    > should be ok for most use cases.
    >

    I read the other branch of this thread too, but IMHO, this would be the
    best solution for now. It's a one line change and does the job. After
    all, we have that priority for a reason, it doesn't makes sense having
    all of them at a common default. As mentioned in an other reply, I think
    it is especially reasonable to configure the syscon-reboot driver a bit
    higher, since this driver is more likely to be used for a dedicated
    reboot feature provided by the SoC, which usually is the preferred one.
    If it happens one day that a SoC ends up with conflicting priorities or
    other priority odds, we can add the DT support then...

    What do you think, can I go with that for now? (Guenter, Feng, Mark...?)

    --
    Stefan



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