On 8/9/2024 10:28 PM, Elliot Berman wrote:
> On Fri, Aug 09, 2024 at 03:30:38PM +0200, Lorenzo Pieralisi wrote:
>> On Wed, Aug 07, 2024 at 11:10:50AM -0700, Elliot Berman wrote:
>>
>> [...]
>>
>>>>> +static void psci_vendor_sys_reset2(unsigned long action, void *data)
>>>>
>>>> 'action' is unused and therefore it is not really needed.
>>>>
>>>>> +{
>>>>> + const char *cmd = data;
>>>>> + unsigned long ret;
>>>>> + size_t i;
>>>>> +
>>>>> + for (i = 0; i < num_psci_reset_params; i++) {
>>>>> + if (!strcmp(psci_reset_params[i].mode, cmd)) {
>>>>> + ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
>>>>> + psci_reset_params[i].reset_type,
>>>>> + psci_reset_params[i].cookie, 0);
>>>>> + pr_err("failed to perform reset \"%s\": %ld\n",
>>>>> + cmd, (long)ret);
>>>>> + }
>>>>> + }
>>>>> +}
>>>>> +
>>>>> static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
>>>>> void *data)
>>>>> {
>>>>> + if (data && num_psci_reset_params)
>>>>
>>>> So, reboot_mode here is basically ignored; if there is a vendor defined
>>>> reset, we fire it off.
>>>>
>>>> I think Mark mentioned his concerns earlier related to REBOOT_* mode and
>>>> reset type (granted, the context was different):
>>>>
>>>> https://lore.kernel.org/all/20200320120105.GA36658@C02TD0UTHF1T.local/
>>>>
>>>> I would like to understand if this is the right thing to do before
>>>> accepting this patchset.
>>>>
>>>
>>> I don't have any concerns to move this part below checking reboot_mode.
>>> Or, I could add reboot_mode == REBOOT_COLD check.
>>
>> The question is how can we map vendor specific reboot magic to Linux
>> reboot modes sensibly in generic PSCI code - that's by definition
>> vendor specific.
>>
>
> I don't think it's a reasonable thing to do. "reboot bootloader" or
> "reboot edl" don't make sense to the Linux reboot modes.
>
> I believe the Linux reboot modes enum is oriented to perspective of
> Linux itself and the vendor resets are oriented towards behavior of the
> SoC.
>
> Thanks,
> Elliot
>
Agree.
from perspective of linux reboot modes, kernel's current implementation in reset path is like:
__
#1 If reboot_mode is WARM/SOFT and PSCI_SYSRESET2 is supported
Call PSCI - SYSTEM_RESET2 - ARCH RESET
#2 ELSE
Call PSCI - SYSTEM_RESET COLD RESET
___
ARM SPECS for PSCI SYSTEM_RESET2
This function extends SYSTEM_RESET. It provides:
• ARCH RESET: set Bit[31] to 0 = > This is already in place in condition #1.
• vendor-specific resets: set Bit[31] to 1. = > current patchset adds this part before kernel's reboot_mode reset at #0.
In current patchset, we see a condition added at #0-psci_vendor_reset2 being called before kernel’s current reboot_mode condition and it can take any action only if all below conditions are satisfied.
- PSCI SYSTEM_RESET2 is supported.
- psci dt node defines an entry "bootloader" as a reboot-modes.
- User issues reboot with a command say - (reboot bootloader).
- If vendor reset fails, default reboot mode will execute as is.
Don't see if we will skip or break the kernel reboot_mode flow with this patch.
Also if user issues reboot <cmd> and <cmd> is supported on SOC vendor reset psci node, should cmd take precedence over kernel reboot mode enum? may be yes?
