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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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