On Mon, Dec 01, 2014 at 05:24:37PM +0000, Stefan Agner wrote: > On 2014-12-01 18:11, Mark Rutland wrote: > > On Mon, Dec 01, 2014 at 05:03:07PM +0000, Stefan Agner 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@xxxxxxxx> > >> --- > >> 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) > >> + > > > > NAK. This is a leak of Linux-internal details. > > > > What is this necessary for? > > > > Mark. > > Hi Mark, > > In my case, it is necessary to be called ahead of the watchdog, which > has a priority of 128. This syscon-reboot driver currently has a default > priority of 128 too. I could live with a higher default priority for the > syscon-reboot driver, in fact I proposed that in the discussion of v1 of > that patch: > https://lkml.org/lkml/2014/11/28/484 Thanks for the link. > IMHO, this priority might make sense for most cases, I guess that > dedicated "syscon" capabilities are usually better suited as a reboot > source than watchdog. I would think likewise. > If dt, then the question which arises: If there are different > capabilities to reset/reboot a whole system, how do we reflect which is > the best suited one in dt? I'm not sure, but I don't think that exposing a priority variable in this way is the best, because it implicitly relies on what the kernel may have selected for other devices and/or FW interfaces, which may not have been described in DT. So if we can get away with a fixed priority for now, then I would prefer that. Otherwise, I would imagine that most systems have a single preferred mechanism with some possible fallback(s), for which a single preferred-poweroff property might suffice, and has better interaction w.r.t. priority (in that it should _always_ be tried first). Even that's difficult to reconcile with FW bindings though, especially EFI (which we sometimes must use in preference for variable storage and capsule updates). Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
