Re: Conflict between video-lut and pmu on meson-g12

[Marc Gonzalez <marc.w.gonzalez@free.fr>]

On 28/02/2023 22:49, Martin Blumenstingl wrote:

> While thinking more about this - I think the whole .dtsi code should
> be improved. Both of the PMU IO regions are part of the &dmc region.
> So I think &pmu should be moved inside &dmc (with the offsets adjusted
> accordingly of course).
> 
> Also I think the dt-bindings are incomplete: according to the driver
> code we're using XTAL as input clock.
> But this is not described anywhere in the dt-bindings.
> dt-bindings should always describe the hardware. The driver can decide
> not to use it but the bindings must always be complete.
> And with this comes the question: is the DMC PLL specific to the PMU
> or is it shared with something else (e.g. the actual memory
> controller)? On the 32-bit SoCs (Meson8b/S805 for example) there's a
> whole DDR clock controller (used by the DDR memory controller), so I'm
> wondering if these newer SoCs are still following that approach.

FWIW, the vendor device-tree specifies the following nodes:
https://android.googlesource.com/kernel/arm64/+/f5269100977385d1fd4a5ef68e49631892cf4fe4/arch/arm64/boot/dts/amlogic/g12a_s905x2_u215.dts

	canvas {
		compatible = "amlogic, meson, canvas";
		dev_name = "amlogic-canvas";
		status = "okay";
		reg = <0x0 0xff638000 0x0 0x2000>;
		phandle = <0x111>;
	};

	codec_io {
		compatible = "amlogic, codec_io";
		status = "okay";
		#address-cells = <0x2>;
		#size-cells = <0x2>;
		ranges;
		phandle = <0x112>;
		[...]
		io_dmc_base {
			reg = <0x0 0xff638000 0x0 0x2000>;
		};
	};

	ddr_bandwidth {
		compatible = "amlogic, ddr-bandwidth";
		status = "okay";
		reg = <0x0 0xff638000 0x0 0x100 0x0 0xff638c00 0x0 0x100>;
		sec_base = <0xff639000>;
		interrupts = <0x0 0x34 0x1>;
		interrupt-names = "ddr_bandwidth";
	};


I don't understand how it's possible to have 3 overlapping ranges?
Unless the respective drivers know to map only specific ranges?


Regarding your DMC (DDR memory controller) clock question,
clock tree seems to be:
24 MHz XTAL feeds DDR_PLL block,
which outputs DDR_CLK pulse for the DMC.


Something I do not understand is that the datasheet states:
DMC unsecure register. Base address 0xFF638000.
Offset 0 = AM_DDR_PLL_CNTL0
Offset 4 = AM_DDR_PLL_CNTL1
...

And then also states:
The following registers' base address is 0xff638000.
Offset 0 = DMC_REQ_CTRL
Offset 4 = DMC_SOFT_RST
...

And these two register sets have nothing in common
(except the SAME base address...)

https://android.googlesource.com/kernel/arm64/+/f5269100977385d1fd4a5ef68e49631892cf4fe4/include/linux/amlogic/media/registers/regs/dmc_regs.h

Is there perhaps a typo in one of the base addresses?


Regards.

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