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Date:   Wed, 6 Mar 2019 08:35:35 +0100
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>, kgene@...nel.org,
        Chanwoo Choi <cw00.choi@...sung.com>,
        kyungmin.park@...sung.com,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        s.nawrocki@...sung.com, myungjoo.ham@...sung.com
Subject: Re: [PATCH v5 4/8] dt-bindings: devfreq: add Exynos5422 DMC device
 description

Hi Krzysztof,

On 3/5/19 12:35 PM, Krzysztof Kozlowski wrote:
> On Tue, 5 Mar 2019 at 11:19, Lukasz Luba <l.luba@...tner.samsung.com> 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>
>> ---
>>   .../devicetree/bindings/devfreq/exynos5422-dmc.txt | 177 +++++++++++++++++++++
>>   1 file changed, 177 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/devfreq/exynos5422-dmc.txt
>>
>> diff --git a/Documentation/devicetree/bindings/devfreq/exynos5422-dmc.txt b/Documentation/devicetree/bindings/devfreq/exynos5422-dmc.txt
>> new file mode 100644
>> index 0000000..0e73e98
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/devfreq/exynos5422-dmc.txt
>> @@ -0,0 +1,177 @@
>> +* 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 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.
>> +
>> +The example definition of a DMC and PPMU devices declared in DT is shown below:
>> +
>> +       ppmu_dmc0_0: ppmu@...00000 {
>> +               compatible = "samsung,exynos-ppmu";
>> +               reg = <0x10d00000 0x2000>;
>> +               clocks = <&clock CLK_PCLK_PPMU_DREX0_0>;
>> +               clock-names = "ppmu";
>> +               status = "okay";
>> +               events {
>> +                       ppmu_event_dmc0_0: ppmu-event3-dmc0_0 {
>> +                               event-name = "ppmu-event3-dmc0_0";
>> +                       };
>> +               };
>> +       };
>> +
>> +
>> +       ppmu_dmc0_1: ppmu@...10000 {
>> +               compatible = "samsung,exynos-ppmu";
>> +               reg = <0x10d10000 0x2000>;
>> +               clocks = <&clock CLK_PCLK_PPMU_DREX0_1>;
>> +               clock-names = "ppmu";
>> +               status = "okay";
>> +               events {
>> +                       ppmu_event_dmc0_1: ppmu-event3-dmc0_1 {
>> +                               event-name = "ppmu-event3-dmc0_1";
>> +                       };
>> +               };
>> +       };
>> +
>> +       ppmu_dmc1_0: ppmu@...10000 {
>> +               compatible = "samsung,exynos-ppmu";
>> +               reg = <0x10d60000 0x2000>;
>> +               clocks = <&clock CLK_PCLK_PPMU_DREX1_0>;
>> +               clock-names = "ppmu";
>> +               status = "okay";
>> +               events {
>> +                       ppmu_event_dmc1_0: ppmu-event3-dmc1_0 {
>> +                               event-name = "ppmu-event3-dmc1_0";
>> +                       };
>> +               };
>> +       };
>> +
>> +       ppmu_dmc1_1: ppmu@...70000 {
>> +               compatible = "samsung,exynos-ppmu";
>> +               reg = <0x10d70000 0x2000>;
>> +               clocks = <&clock CLK_PCLK_PPMU_DREX1_1>;
>> +               clock-names = "ppmu";
>> +               status = "okay";
>> +               events {
>> +                       ppmu_event_dmc1_1: ppmu-event3-dmc1_1 {
>> +                               event-name = "ppmu-event3-dmc1_1";
>> +                       };
>> +               };
>> +       };
>> +
>> +       dmc: memory-controller@...20000 {
>> +               compatible = "samsung,exynos5422-dmc";
>> +               reg = <0x10c20000 0x10000>, <0x10c30000 0x10000>,
>> +                       <0x10000000 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 CLK_CDREX_PAUSE>,
>> +                               <&clock CLK_CDREX_TIMING_SET>;
>> +               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",
>> +                               "clk_cdrex_pause",
>> +                               "clk_cdrex_timing_set";
>> +               status = "okay";
>> +               operating-points-v2 = <&dmc_opp_table>;
>> +               devfreq-events = <&ppmu_dmc0_0>, <&ppmu_dmc0_1>,
>> +                               <&ppmu_dmc1_0>, <&ppmu_dmc1_1>;
>> +       };
>> +
>> +The needed timings of DRAM memory are stored in dedicated nodes.
>> +There are two nodes with regular timings and for bypass mode.
>> +
>> +       dmc_bypass_mode: bypass_mode {
>> +               compatible = "samsung,dmc-bypass-mode";
> 
> This looks like an example, not bindings.
I have not seen similar, since it is not just 'timing' but other
Exynos register specific stuff in the register.
> 
>> +
>> +               freq-hz = <400000000>;
>> +               volt-uv = <887500>;
> 
> -microvolt
> Documentation/devicetree/bindings/property-units.txt
Thanks
> 
>> +               dram-timing-row = <0x365a9713>;
>> +               dram-timing-data = <0x4740085e>;
>> +               dram-timing-power = <0x543a0446>;
>> +       };
>> +
>> +       dram_timing: timing {
>> +               compatible = "samsung,dram-timing";
> 
> Probably you should use timings from Documentation/devicetree/bindings/lpddr2/
> If not, all the fields below should be described.
It is not just 'timing'. It is a whole register specific value for the
Exynos5422. It could be named 'dram-config-regs' to avoid confusion.
The regs are called 'row', 'data' and 'power' and adding a procedure
in the driver which takes ~30 values for each speed-grade and combines
into a reg value makes no sense.
> 
> All these bindings (memory-controller, timings) look like description
> of memory controller so maybe they should go into
> Documentation/devicetree/bindings/memory-controllers ?
I don't know, maybe Chanwoo has some opinion since he requested to put
these register values into DT.

Regards,
Lukasz
> 
> Best regards,
> Krzysztof
> 
>> +
>> +               dram-timing-names = "165MHz", "206MHz", "275MHz", "413MHz",
>> +                                   "543MHz", "633MHz", "728MHz", "825MHz";
>> +               dram-timing-row = <0x11223185>, <0x112331C6>, <0x12244287>,
>> +                                 <0x1B35538A>, <0x244764CD>, <0x2A48758F>,
>> +                                 <0x30598651>, <0x365A9713>;
>> +               dram-timing-data = <0x2720085E>, <0x2720085E>, <0x2720085E>,
>> +                                  <0x2720085E>, <0x3730085E>, <0x3730085E>,
>> +                                  <0x3730085E>, <0x4740085E>;
>> +               dram-timing-power = <0x140C0225>, <0x180F0225>, <0x1C140225>,
>> +                                   <0x2C1D0225>, <0x38270335>, <0x402D0335>,
>> +                                   <0x4C330336>, <0x543A0446>;
>> +       };
>> +
>> +The frequencies supported by the DMC are stored in OPP table v2.
>> +
>> +       dmc_opp_table: opp_table2 {
>> +               compatible = "operating-points-v2";
>> +
>> +               opp00 {
>> +                       opp-hz = /bits/ 64 <165000000>;
>> +                       opp-microvolt = <875000>;
>> +               };
>> +               opp01 {
>> +                       opp-hz = /bits/ 64 <206000000>;
>> +                       opp-microvolt = <875000>;
>> +               };
>> +               opp02 {
>> +                       opp-hz = /bits/ 64 <275000000>;
>> +                       opp-microvolt = <875000>;
>> +               };
>> +               opp03 {
>> +                       opp-hz = /bits/ 64 <413000000>;
>> +                       opp-microvolt = <887500>;
>> +               };
>> +               opp04 {
>> +                       opp-hz = /bits/ 64 <543000000>;
>> +                       opp-microvolt = <937500>;
>> +               };
>> +               opp05 {
>> +                       opp-hz = /bits/ 64 <633000000>;
>> +                       opp-microvolt = <1012500>;
>> +               };
>> +               opp06 {
>> +                       opp-hz = /bits/ 64 <728000000>;
>> +                       opp-microvolt = <1037500>;
>> +               };
>> +               opp07 {
>> +                       opp-hz = /bits/ 64 <825000000>;
>> +                       opp-microvolt = <1050000>;
>> +               };
>> +       };
>> +
>> --
>> 2.7.4
>>
> 
> 

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