linux-kernel - Re: [PATCH v2] firmware/psci: add support for SYSTEM

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Message-ID: <d2eaaf6d-01f9-2daa-ea1f-3396e3b93104@xilinx.com>
Date:   Thu, 19 Jul 2018 12:47:51 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        Michal Simek <michal.simek@...inx.com>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     Mark Rutland <mark.rutland@....com>, Will Wong <WILLW@...inx.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        <linux-kernel@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v2] firmware/psci: add support for SYSTEM_RESET2

On 9.7.2018 15:21, Sudeep Holla wrote:
> 
> 
> On 09/07/18 14:13, Michal Simek wrote:
>> On 9.7.2018 14:36, Sudeep Holla wrote:
>>>
>>>
>>> On 09/07/18 13:17, Michal Simek wrote:
>>>> Hi Sudeep,
>>>>
>>>> On 2.5.2018 12:30, Sudeep Holla wrote:
>>>>> PSCI v1.1 introduced SYSTEM_RESET2 to allow both architectural resets
>>>>> where the semantics are described by the PSCI specification itself as
>>>>> well as vendor-specific resets. Currently only system warm reset
>>>>> semantics is defined as part of architectural resets by the specification.
>>>>>
>>>>> This patch implements support for SYSTEM_RESET2 by making using of
>>>>> reboot_mode passed by the reboot infrastructure in the kernel.
>>>>>
>>>>> Cc: Mark Rutland <mark.rutland@....com>
>>>>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>>>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>>>>> ---
>>>>>  drivers/firmware/psci.c   | 21 +++++++++++++++++++++
>>>>>  include/uapi/linux/psci.h |  2 ++
>>>>>  2 files changed, 23 insertions(+)
>>>>>
>>>>> v1->v2:
>>>>> 	- Added mising static anotation to psci_system_reset2_supported
>>>>> 	- Added missing ')' in the comment
>>>>>
>>>>> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
>>>>> index c80ec1d03274..91748725534e 100644
>>>>> --- a/drivers/firmware/psci.c
>>>>> +++ b/drivers/firmware/psci.c
>>>>> @@ -88,6 +88,7 @@ static u32 psci_function_id[PSCI_FN_MAX];
>>>>>  				PSCI_1_0_EXT_POWER_STATE_TYPE_MASK)
>>>>>
>>>>>  static u32 psci_cpu_suspend_feature;
>>>>> +static bool psci_system_reset2_supported;
>>>>>
>>>>>  static inline bool psci_has_ext_power_state(void)
>>>>>  {
>>>>> @@ -253,6 +254,15 @@ static int get_set_conduit_method(struct device_node *np)
>>>>>
>>>>>  static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
>>>>>  {
>>>>> +	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
>>>>
>>>> I am curious about this reboot_mode setup. I have grepped the kernel and
>>>> reboot_mode is setup via kernel parameters at boot time.
>>>> Shouldn't user decide what reboot type wants to do?
>>>>
>>>
>>> I have almost forgotten how I tested this. IIRC and looking quickly @
>>> kernel/reboot.c and __setup(reboot=,...), I recall passing reboot=w
>>> while testing this.
>>
>> I would expect that too. It means static setting at boot time.
>>
>>> We can do something like what efi_reboot, but not
>>> sure if we need that yet if users need too decide after boot.
>>
>>
>> I am checking with colleague about all xilinx use cases but I would be
>> surprised if static configuration at run time is enough.
>>
>> Also not quite sure about mixing reboot_warm and reboot_soft cases
>> together. They shouldn't be the same.
>>
>> Based on psci 1.0 spec there are more options especially for bit[31]
>> which should be likely setup via DT(no experience with EFI) with names
>> and codes which should be passed to firmware but still the same issue
>> remains how to setup reboot type.
>>
> 
> I think with efi_reboot, if user execute the command "reboot warm", it
> will set REBOOT_WARM. I was thinking something similar for psci too. I
> can drop REBOOT_SOFT if that's not correct.

Have you found more details about efi_reboot and passing information in
case of reboot warm?

Thanks,
Michal