Re: [PATCH v5 1/5] dt-bindings: gpu: add bindings for the ARM Mali Midgard GPU

[Heiko Stübner]

Hi Brian,

Am Mittwoch, 12. Juli 2017, 10:26:39 CEST schrieb Brian Norris:
> Hi Guillaume,
> 
> I know this has already been merged, but I figured here was an OK place
> to note (inline):
> 
> On Wed, May 03, 2017 at 10:56:25AM +0100, Guillaume Tucker wrote:
> > The ARM Mali Midgard GPU family is present in a number of SoCs
> > from many different vendors such as Samsung Exynos and Rockchip.
> > 
> > Import the device tree bindings documentation from the r16p0
> > 
> > release of the Mali Midgard GPU kernel driver:
> >   https://developer.arm.com/-/media/Files/downloads/mali-drivers/kernel/ma
> >   li-midgard-gpu/TX011-SW-99002-r16p0-00rel0.tgz> 
> > Remove the copyright and GPL licence header as deemed not necessary.
> > 
> > Redesign the "compatible" property strings to list all the Mali
> > Midgard GPU types and add vendor specific ones.
> > 
> > Drop the "clock-names" property as the Mali Midgard GPU uses only one
> > clock (the driver now needs to call clk_get with NULL).
> > 
> > Convert the "interrupt-names" property values to lower-case: "job",
> > "mmu" and "gpu".
> > 
> > Replace the deprecated "operating-points" optional property with
> > "operating-points-v2".
> > 
> > Omit the following optional properties in this initial version as they
> > 
> > are only used in very specific cases:
> >   * snoop_enable_smc
> >   * snoop_disable_smc
> >   * jm_config
> >   * power_model
> >   * system-coherency
> >   * ipa-model
> > 
> > Update the example accordingly to reflect all these changes, based on
> > rk3288 mali-t760.
> > 
> > CC: John Reitan <john.reitan@xxxxxxx>
> > Tested-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> > Signed-off-by: Guillaume Tucker <guillaume.tucker@xxxxxxxxxxxxx>
> > ---
> > 
> >  .../devicetree/bindings/gpu/arm,mali-midgard.txt   | 86
> >  ++++++++++++++++++++++ 1 file changed, 86 insertions(+)
> >  create mode 100644
> >  Documentation/devicetree/bindings/gpu/arm,mali-midgard.txt> 
> > diff --git a/Documentation/devicetree/bindings/gpu/arm,mali-midgard.txt
> > b/Documentation/devicetree/bindings/gpu/arm,mali-midgard.txt new file
> > mode 100644
> > index 000000000000..d3b6e1a4713a
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/gpu/arm,mali-midgard.txt
> 
> ^^ This file name implies we're talking about a base "arm,mali-midgard"
> compatible property.

it follows the precedent of arm,mali-utgard.txt and while the file-name
is not part of the compatible list, it feels way better collecting all the 
variants in one file, compared to spawning multiple ones for each soc
vendor using a mali gpu.

Also in other places the naming of binding descriptions does not follow
any compatible at all, so the filename = main-compatible does not seem
to be the rule.


> > @@ -0,0 +1,86 @@
> > +ARM Mali Midgard GPU
> > +====================
> > +
> > +Required properties:
> > +
> > +- compatible :
> > +  * Must contain one of the following:
> > +    + "arm,mali-t604"
> > +    + "arm,mali-t624"
> > +    + "arm,mali-t628"
> > +    + "arm,mali-t720"
> > +    + "arm,mali-t760"
> > +    + "arm,mali-t820"
> > +    + "arm,mali-t830"
> > +    + "arm,mali-t860"
> > +    + "arm,mali-t880"
> > +  * which must be preceded by one of the following vendor specifics:
> > +    + "amlogic,meson-gxm-mali"
> > +    + "rockchip,rk3288-mali"
> 
> But it's not listed here.
> 
> > +
> > +- reg : Physical base address of the device and length of the register
> > area. +
> > +- interrupts : Contains the three IRQ lines required by Mali Midgard
> > devices. +
> > +- interrupt-names : Contains the names of IRQ resources in the order they
> > were +  provided in the interrupts property. Must contain: "job", "mmu",
> > "gpu". +
> > +
> > +Optional properties:
> > +
> > +- clocks : Phandle to clock for the Mali Midgard device.
> > +
> > +- mali-supply : Phandle to regulator for the Mali device. Refer to
> > +  Documentation/devicetree/bindings/regulator/regulator.txt for details.
> > +
> > +- operating-points-v2 : Refer to
> > Documentation/devicetree/bindings/power/opp.txt +  for details.
> > +
> > +
> > +Example for a Mali-T760:
> > +
> > +gpu@ffa30000 {
> > +	compatible = "rockchip,rk3288-mali", "arm,mali-t760",
> > "arm,mali-midgard";
> 
> And it *is* used here in this example.
> 
> So, should it be used/documented or not?

No I don't think it should and have patches that drop the mali-midgard from
the example + rk3288 dtsi to not confuse people:
- https://patchwork.kernel.org/patch/9832811/
- https://patchwork.kernel.org/patch/9832807/


Devicetree supposedly should not contain wildcards and without knowing
for real that all of then in fact are compatible we should not assume so
[and that's hard to check with all the secrecy :-) ] . Using the real name 
(tXXX) sounds nice enough.


Heiko

> > +	reg = <0xffa30000 0x10000>;
> > +	interrupts = <GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>,
> > +		     <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>,
> > +		     <GIC_SPI 8 IRQ_TYPE_LEVEL_HIGH>;
> > +	interrupt-names = "job", "mmu", "gpu";
> > +	clocks = <&cru ACLK_GPU>;
> > +	mali-supply = <&vdd_gpu>;
> > +	operating-points-v2 = <&gpu_opp_table>;
> > +	power-domains = <&power RK3288_PD_GPU>;
> > +};
> 
> [...]
> 
> Brian