Re: [PATCH 0/3] Allwinner sunxi message box support

[Samuel Holland]

Hi,

On 02/28/18 02:24, Maxime Ripard wrote:
> On Tue, Feb 27, 2018 at 08:27:11PM -0600, Samuel Holland wrote:
>> This series adds support for the "hardware message box" in recent
>> Allwinner sunxi SoCs, used for communication with the ARISC management
>> processor (the platform's equivalent of the ARM SCP). The end goal is to
>> use the arm_scpi driver as a client, communicating with firmware running
>> on the ARISC CPU.
>>
>> This driver has been tested with the base arm_scpi driver (which sends
>> the SCPI_CMD_SCPI_CAPABILITIES command at probe time) and an in-progress
>> firmware application running on the ARISC CPU. Because no firmware for
>> the other end of the mailbox is complete at the moment, I have not
>> included changes to the SoC device trees.
> 
> This is not directly related to this series, but what is your end goal
> with regard to SCPI? What features do you expect to have there?

Current plans are to support in SCPI:
- SMP bringup and CPU hotplug (via PSCI in ATF)
- System reset and poweroff (via PSCI in ATF)
- System standby and suspend (via PSCI in ATF)
- DVFS for ARM CPUs
- Clock control for clocks in R_PRCM (e.g. R_CIR_RX)
- Thermal sensor reading

Other planned features of the firmware:
- System wakeup from poweroff (via GPIO or interrupt to firmware)
- System power/suspend LED control (connected to GPIO or PMIC GPIO)
- Polling of thermal sensor in firmware for thermal throttling

> I'm asking because last time we discussed this, SCPI wasn't able to abstract
> all the features the PMIC provides, and thus Linux needed to still be able to
> access it.

This should only be an issue for devices with AXP PMICs. Other devices with GPIO
or simple IÂC regulator control, such as H3 and H5 boards, can have all
necessary features described with standard SCPI commands. SCPI provides for 127
vendor-defined "extended" commands, which could be used to build a full AXP PMIC
driver, or simply provide commands to read/write PMIC registers.

For the moment I'm not concerned with battery powered devices. So right now the
relevant boards either a) don't have a PMIC, or b) can have everything but DVFS
voltage hard-coded in the firmware.

> Thanks!
> Maxime

Regards,
Samuel