linux-kernel - Re: [PATCH v6 06/10] dt-bindings: memory-controllers: add Exynos5422 DMC device description

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Date:   Mon, 29 Apr 2019 14:14:33 +0200
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     Rob Herring <robh@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        b.zolnierkie@...sung.com, krzk@...nel.org, kgene@...nel.org,
        cw00.choi@...sung.com, kyungmin.park@...sung.com,
        m.szyprowski@...sung.com, s.nawrocki@...sung.com,
        myungjoo.ham@...sung.com, keescook@...omium.org, tony@...mide.com,
        jroedel@...e.de, treding@...dia.com, digetx@...il.com,
        willy.mh.wolff.ml@...il.com
Subject: Re: [PATCH v6 06/10] dt-bindings: memory-controllers: add
 Exynos5422 DMC device description

Hi Rob,

On 4/25/19 9:57 PM, Rob Herring wrote:
> On Fri, Apr 19, 2019 at 04:19:24PM +0200, Lukasz Luba wrote:
>> The patch adds description for DT binding for a new Exynos5422 Dynamic
>> Memory Controller device.
>>
>> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
>> ---
>>   .../bindings/memory-controllers/exynos5422-dmc.txt | 73 ++++++++++++++++++++++
>>   1 file changed, 73 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt
>>
>> diff --git a/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt b/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt
>> new file mode 100644
>> index 0000000..133b3cc
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt
>> @@ -0,0 +1,73 @@
>> +* Exynos5422 frequency and voltage scaling for Dynamic Memory Controller device
>> +
>> +The Samsung Exynos5422 SoC has DMC (Dynamic Memory Controller) to which the DRAM
>> +memory chips are connected. The driver is to monitor the controller in runtime
>> +and switch frequency and voltage. To monitor the usage of the controller in
>> +runtime, the driver uses the PPMU (Platform Performance Monitoring Unit), which
>> +is able to measure the current load of the memory.
>> +When 'userspace' governor is used for the driver, an application is able to
>> +switch the DMC and memory frequency.
>> +
>> +Required properties for DMC device for Exynos5422:
>> +- compatible: Should be "samsung,exynos5422-bus".
>> +- clock-names : the name of clock used by the bus, "bus".
>> +- clocks : phandles for clock specified in "clock-names" property.
>> +- devfreq-events : phandles for PPMU devices connected to this DMC.
>> +- vdd-supply : phandle for voltage regulator which is connected.
>> +- reg : registers of two CDREX controllers, chip information, clocks subsystem.
>> +- operating-points-v2 : phandle for OPPs described in v2 definition.
>> +- device-handle : phandle of the connected DRAM memory device. For more
>> +	information please refer to Documentation
> 
> The memory node(s) should be a child of the memory controller IMO.
I have followed the TI code for LPDDR2. They use 'device-handle'
probably because the memory controller can be moved into the common
.dtsi and taken by reference in .dts in a proper board file.
The board .dts files might specify different DRAM chips and timings.
In Exynos case we will also have such situation: one memory controller
and a few different DRAM chips.

> 
>> +- devfreq-events : phandles of the PPMU events used by the controller.
>> +
>> +Example:
>> +
>> +	ppmu_dmc0_0: ppmu@...00000 {
>> +		compatible = "samsung,exynos-ppmu";
>> +		reg = <0x10d00000 0x2000>;
>> +		clocks = <&clock CLK_PCLK_PPMU_DREX0_0>;
>> +		clock-names = "ppmu";
>> +		status = "okay";
> 
> Don't show 'status' in examples.
Thank you, I accidentally copied it from dt file.

Regards,
Lukasz
> 
>> +		events {
>> +			ppmu_event_dmc0_0: ppmu-event3-dmc0_0 {
>> +				event-name = "ppmu-event3-dmc0_0";
>> +			};
>> +		};
>> +	};
>> +
>> +	dmc: memory-controller@...20000 {
>> +		compatible = "samsung,exynos5422-dmc";
>> +		reg = <0x10c20000 0x10000>, <0x10c30000 0x10000>,
>> +			<0x10000000 0x1000>, <0x10030000 0x1000>;
>> +		clocks = 	<&clock CLK_FOUT_SPLL>,
>> +				<&clock CLK_MOUT_SCLK_SPLL>,
>> +				<&clock CLK_FF_DOUT_SPLL2>,
>> +				<&clock CLK_FOUT_BPLL>,
>> +				<&clock CLK_MOUT_BPLL>,
>> +				<&clock CLK_SCLK_BPLL>,
>> +				<&clock CLK_MOUT_MX_MSPLL_CCORE>,
>> +				<&clock CLK_MOUT_MX_MSPLL_CCORE_PHY>,
>> +				<&clock CLK_MOUT_MCLK_CDREX>,
>> +				<&clock CLK_DOUT_CLK2X_PHY0>,
>> +				<&clock CLK_CLKM_PHY0>,
>> +				<&clock CLK_CLKM_PHY1>;
>> +		clock-names =	"fout_spll",
>> +				"mout_sclk_spll",
>> +				"ff_dout_spll2",
>> +				"fout_bpll",
>> +				"mout_bpll",
>> +				"sclk_bpll",
>> +				"mout_mx_mspll_ccore",
>> +				"mout_mx_mspll_ccore_phy",
>> +				"mout_mclk_cdrex",
>> +				"dout_clk2x_phy0",
>> +				"clkm_phy0",
>> +			        "clkm_phy1";
>> +		status = "okay";
>> +		operating-points-v2 = <&dmc_opp_table>;
>> +		devfreq-events = <&ppmu_event3_dmc0_0>,	<&ppmu_event3_dmc0_1>,
>> +				<&ppmu_event3_dmc1_0>, <&ppmu_event3_dmc1_1>;
>> +		operating-points-v2 = <&dmc_opp_table>;
>> +		device-handle = <&samsung_K3QF2F20DB>;
>> +		vdd-supply = <&buck1_reg>;
>> +	};
>> -- 
>> 2.7.4
>>
> 
>