Re: [PATCH v2 2/2] ARM: sun8i: dt: Add mali node

[Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Mon, Jan 30, 2017 at 8:00 AM, Maxime Ripard
<maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> Hi Rob,
>
> On Fri, Jan 27, 2017 at 02:21:19PM -0600, Rob Herring wrote:
>> On Mon, Jan 23, 2017 at 03:00:46PM +0100, Maxime Ripard wrote:
>> > The A23 and A33 have an ARM Mali 400 GPU. Now that we have a binding, add
>> > it to our DT.
>> >
>> > Signed-off-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
>> > ---
>> >  arch/arm/boot/dts/sun8i-a23-a33.dtsi | 26 ++++++++++++++++++++++++++
>> >  1 file changed, 26 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/arch/arm/boot/dts/sun8i-a23-a33.dtsi b/arch/arm/boot/dts/sun8i-a23-a33.dtsi
>> > index e4991a78ad73..982705719ef2 100644
>> > --- a/arch/arm/boot/dts/sun8i-a23-a33.dtsi
>> > +++ b/arch/arm/boot/dts/sun8i-a23-a33.dtsi
>> > @@ -486,6 +486,32 @@
>> >                     #size-cells = <0>;
>> >             };
>> >
>> > +           mali: gpu@01c40000 {
>>
>> Drop leading 0.
>>
>> > +                   compatible = "allwinner,sun8i-a23-mali",
>> > +                                "allwinner,sun7i-a20-mali", "arm,mali-400";
>> > +                   reg = <0x01c40000 0x10000>;
>>
>> Does this really use 64K or that's just the register spacing? Set it
>> to what's used.
>
> The memory maps in our datasheet allocates 64k for that block. I
> always thought that we had to put the size of the whole memory block
> allocated to that device.
>
> For now, the driver only uses space up to 0xe000 (so we wouldn't
> "waste" a lot of space anyway), but what if at some point the driver
> needs more than what we put in the DT?

Well, it should be what the h/w is, not what the driver needs.

I only asked because 64K spacing of peripherals is becoming common,
but that wastes a bit of virtual address space on 32-bit if really the
h/w registers are only <4KB. Given that it is 0xe000 in this case, it
doesn't really matter here.

Rob
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