Hi David,
On 26 Sep 2024, at 16:30, David Woodhouse dwmw2@infradead.org wrote:
On Thu, 2024-09-26 at 09:56 +0000, Miguel Luis wrote:
+/* PSCI v1.3 hibernate type for SYSTEM_OFF2 */ +#define PSCI_1_3_HIBERNATE_TYPE_OFF 0
Should it be 1 as hibernate type?
It is in discovery, as BIT(PSCI_1_3_HIBERNATE_TYPE_OFF) == 1<<0 == 1.
Now I see the definition for PSCI_1_3_HIBERNATE_TYPE_OFF was misleading for me when BIT(PSCI_1_3_HIBERNATE_TYPE_OFF) works for both discovery and as argument for SYSTEM_OFF2.
The common factor being the bit offset in the bitmap for SYSTEM_OFF2 discovery and argument to call SYSTEM_OFF2 as well. Would it be clearer something like:
#define PSCI_1_3_HIBERNATE_TYPE_OFF BIT(0)
Assuming future definitions would keep the same common factor can be helpful, however please let me know whether I am missing something.
Thanks, Miguel
But using a bitmask was only supposed to be for the discovery with PSCI_FEATURES, as that has to advertise all the available hibernation types.
The actual SYSTEM_OFF2 call was supposed to just take the numeric value as an argument, since obviously *that* one isn't a bitmask.
Except... I see that now the spec has finally been updated, it seems to say that 0x1 is the value to pass to the SYSTEM_OFF2 call for HIBERNATE_OFF, not 0x0. Which doesn't seem to make much sense, and I don't recall it being what we discussed. Souvik, what happened there?
My understanding was that for each supported hibernation type #n, for which HIBERERNATE_OFF is zero), the PSCI_FEATURES query would include the bit (1<<n) to indicate that it is supported, and then the actual SYSTEM_OFF2 call parameter would be (n) itself, precisely as implemented here.
But the spec now seems to say that HIBERNATE_OFF is advertised as (1<<0) in PSCI_FEATURES, but invoked with the value (1).
Is it too late to fix?
If it isn't just a thinko, what is the intent in the current spec?
If we have new hibernate types such that
#define PSCI_1_3_HIBERNATE_TYPE_OFF 0 #define PSCI_1_3_HIBERNATE_TYPE_FOO 1 #define PSCI_1_3_HIBERNATE_TYPE_BAR 2
It seems obvious that the PSCI_FEATURES response will contain (1<<0), (1<<1) and (1<<2) for them respectively, but what is supposed to be passed to the actual SYSTEM_OFF2 call? Is it always just going to be (PSCI_1_3_HIBERNATE_TYPE_xxx + 1)?
I think we should just fix ยง5.1.10 to report that 0x0 is HIBERNATE_OFF, yes?