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

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Message-ID: <8b08583c-121f-347a-700a-17b5d7784309@arm.com>
Date:   Mon, 9 Jul 2018 14:21:50 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Michal Simek <michal.simek@...inx.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        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 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.

-- 
Regards,
Sudeep