linux-kernel - Re: [PATCH v2 3/3] ARM64: dts: meson-gx: Add MALI nodes for GXBB and GXL

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Date:   Sat, 4 Mar 2017 13:38:04 +0100
From:   Andreas Färber <afaerber@...e.de>
To:     Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     devicetree@...r.kernel.org, sboyd@...eaurora.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        carlo@...one.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/3] ARM64: dts: meson-gx: Add MALI nodes for GXBB and
 GXL

Am 03.03.2017 um 20:29 schrieb Kevin Hilman:
> Neil Armstrong <narmstrong@...libre.com> writes:
>> On 03/02/2017 01:31 PM, Andreas Färber wrote:
>>> Am 01.03.2017 um 11:46 schrieb Neil Armstrong:
>>>> The same MALI-450 MP3 GPU is present in the GXBB and GXL SoCs.
[...]
>>>> The node is simply added in the meson-gxbb.dtsi file.
[...]
>>>> For GXL, since a lot is shared with the GXM that has a MALI-T820 IP, this
>>>> patch adds a new meson-gxl-mali.dtsi and is included in the SoC specific
>>>> dtsi files.
>>>
>>> This part is slightly confusing though.
>>>
>>> What exactly is the GXL vs. GXM difference that this can't be handled by
>>> overriding node properties compatible/interrupts/clocks? I am missing a
>>> GXM patch in this series as rationale for doing it this way.
>>>
>>> In particular I am wondering whether the whole GXM-inherits-from-GXL
>>> concept is flawed and should be adjusted if this leads to secondary
>>> .dtsi files like this: My proposal would be to instead create a
>>> meson-gxl-gxm.dtsi, that meson-gxl.dtsi and meson-gxm.dtsi can inherit
>>> the current common parts from, then the Mali bits can simply go into
>>> meson-gxl.dtsi without extra #includes needed in S905X and S905D. While
>>> it's slightly more work to split once again, I think it would be cleaner.
[...]
>> The only changes are :
[...]
>>  - A different Mali core, but with the same interrupts (less but they share the same lower interrupts), clocks and memory space
>>
>> This is why it was decided to have a sub-dtsi, having a secondary dtsi will simply copy 99% of the GXL dtsi,
>> but surely we could also have an intermediate dtsi but for boards I'm ok with it, but less for a SoC dtsi,
>> since it could lead to some confusion.
>>
>> Finally, yes I could have added the mali node to the GXL dtsi, but the midgard Mali dt-bindings are not upstream
>> and the family is too big and recent enough to consider having stable bindings for now.
>>
>> Nevertheless, nothing is final, this gxl-mali.dtsi could be merged into the GXL dtsi in the future when we
>> have proper dt-bindings and a real support of the T820 Mali on the S912.
>>
>> Kevin, what's your thought about this ?
> 
> I don't have a strong preference.  I'm OK with a separate Mali .dtsi due
> to the signficant overlap between GXL/GXM in terms of clocks, interrupts
> etc.
> 
> However, if the plan is to #include this from GXM .dts files, whould a
> better name be meson-gx-mali.dtsi?

I thought the purpose was specifically to not have GXM include it
because it uses a Midgard IP.

If you want to share the fragment with GXBB too (gx), we should rather
use meson-gx-mali-utgard.dtsi, which would differentiate from GXM's
Midgard while still allowing for variation on the 4xx side (e.g., 470).

Regards,
Andreas

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