Re: [PATCH 1/2] dt-bindings: remoteproc: imx_rproc: Support i.MX8MN/P MMIO

[Marek Vasut <marex@denx.de>]

On 7/10/23 17:09, Rob Herring wrote:
> On Mon, Jul 10, 2023 at 11:10:48AM +0200, Marek Vasut wrote:
>> On 7/10/23 10:13, Krzysztof Kozlowski wrote:
>>> On 08/07/2023 01:26, Marek Vasut wrote:
>>>> The MX8M CM7 boot via SMC call is problematic, since not all versions
>>>> of ATF support this interface. Document MMIO support used to boot the
>>>> CM7 on MX8MN/MP instead and discern MMIO interface using DT compatible
>>>> string. Document GPR register syscon phandle which is required by the
>>>> MMIO interface too.
>>>>
>>>> Signed-off-by: Marek Vasut <marex@denx.de>
>>>> ---
>>>> Note that the MMIO being discerned using compatible string is similar
>>>> approach to "st,stm32mp1-rcc" vs "st,stm32mp1-rcc-secure".
>>>> ---
>>>
>>> Same hardware should not have two compatibles, depending on the bus it is.
>>
>> Yes, I know, but for whatever reason the ST does, so I picked the same
>> approach here. What else would you suggest, boolean properly like Peng wrote
>> ?
>>
>> The compatible is also easier to handle on driver level, at least in Linux,
>> see 2/2 .
> 
> IIRC, in the ST case, the programming model presented to the OS is
> different, so different compatibles. Seems like this case is similar.
> 
> However, can't you try and SMC call and if it fails, use MMIO?

They already do that to determine the CM4 CPU state, and if the SMC 
errors out, then they indicate the CPU is detached. So no, not to my 
knowledge, which indeed would be my preferred solution though.