Re: [PATCH v7 07/13] dt-bindings: memory-controllers: add Exynos5422 DMC device description

From: Lukasz Luba
Date: Wed May 08 2019 - 05:46:22 EST

On 5/8/19 9:19 AM, Krzysztof Kozlowski wrote:
> On Tue, 7 May 2019 at 19:04, Rob Herring <robh@xxxxxxxxxx> wrote:
>>> +- devfreq-events : phandles of the PPMU events used by the controller.
>>> +- samsung,syscon-chipid : phandle of the ChipID used by the controller.
>>> +- samsung,syscon-clk : phandle of the clock register set used by the controller.
>> Looks like a hack. Can't you get this from the clocks property? What is
>> this for?
> Hi Rob,
> Lukasz uses these two syscon regmaps to read certain registers. For
> chipid he reads it to check the size of attached memory (only 2 GB
> version is supported). This indeed looks like a hack. However the
> second regmap (clk) is needed to get the timing data from registers
> from DMC clock driver address space. These are registers with memory
> timing so their data is not exposed anyway in common clk framework.
> Best regards,
> Krzysztof

Thank you Krzysztof for a fast response. I have also responded to Rob.
I wouldn't call accessing chipid registers as a hack, though. The DMC
registers do not contain information about the memory chip since it is
in phase of production the board not the chip. Thus, chipid regs (which
loads from e-fuses) are best place to put information about memory