Re: [PATCH v4 10/18] soc: imx: add i.MX8M blk-ctrl driver

[Lucas Stach <l.stach@pengutronix.de>]

Hi Benjamin,

Am Dienstag, dem 14.09.2021 um 17:46 +0200 schrieb Benjamin Gaignard:
> Le 10/09/2021 à 22:26, Lucas Stach a écrit :
> > This adds a driver for the blk-ctrl blocks found in the i.MX8M* line of
> > SoCs. The blk-ctrl is a top-level peripheral located in the various *MIX
> > power domains and interacts with the GPC power controller to provide the
> > peripherals in the power domain access to the NoC and ensures that those
> > peripherals are properly reset when their respective power domain is
> > brought back to life.
> > 
> > Software needs to do different things to make the bus handshake happen
> > after the GPC *MIX domain is powered up and before it is powered down.
> > As the requirements are quite different between the various blk-ctrls
> > there is a callback function provided to hook in the proper sequence.
> > 
> > The peripheral domains are quite uniform, they handle the soft clock
> > enables and resets in the blk-ctrl address space and sequencing with the
> > upstream GPC power domains.
> 
> Hi Lucas,
> 
> I have tried to use your patches for IMX8MQ but it seems that the hardware
> have different architecture.
> On IMX8MQ there is only one VPU domain for G1 and G2 and that doesn't match
> with your implementation where it is needed to have "bus" and devices power domain.
>  From what I experiment in current IMX8MQ implementation of blk-ctrl (inside VPU driver)
> enabling the 3 clocks (bus, G1, G2) is needed to reset the VPUs.
> 
> Do you think you can update your design to take care of these hardware variations ?

The clocking/reset of the blk-ctrl and ADB in the i.MX8MQ VPU power
domain is really a bit strange, as the ADB reset is tied to the VPU
resets and the clk-ctrl seem to require all 3 VPU clocks, instead of
only the bus clock as in newer designs. However I was able to make it
work with the existing blk-ctrl driver design.

My current WIP patches (only tested with the G1 core so far) on top of
the v5 of the series I just sent out can be found here:
https://git.pengutronix.de/cgit/lst/linux/log/?h=imx8mq-vpu-blk-ctrl

Hope this helps.

Regards,
Lucas