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Date: Fri, 23 Jan 2015 16:44:54 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc: tomasz.figa@...il.com, mturquette@...aro.org, kgene@...nel.org,
pankaj.dubey@...sung.com, inki.dae@...sung.com,
chanho61.park@...sung.com, sw0312.kim@...sung.com,
linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/12] clk: samsung: exynos5433: Add clocks using common
clock framework
Hi Sylwester,
On 01/23/2015 01:47 AM, Sylwester Nawrocki wrote:
> Hi Chanwoo,
>
> On 21/01/15 07:26, Chanwoo Choi wrote:
>> This patch adds the support for CMU (Clock Management Units) of Exynos5433
>> which is 64bit SoC and has Octa-cores. This patch supports necessary clocks
>> (PLL/MMC/UART/MCT/I2C/SPI) for kernel boot and includes binding documentation
>> for Exynos5433 clock controller.
>
>> diff --git a/Documentation/devicetree/bindings/clock/exynos5433-clock.txt b/Documentation/devicetree/bindings/clock/exynos5433-clock.txt
>> new file mode 100644
>> index 0000000..72cd0ba
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/clock/exynos5433-clock.txt
>> @@ -0,0 +1,106 @@
>> +* Samsung Exynos5433 CMU (Clock Management Units)
>> +
>> +The Exynos5433 clock controller generates and supplies clock to various
>> +controllers within the Exynos5433 SoC.
>> +
>> +Required Properties:
>> +
>> +- compatible: should be one of the following.
>> + - "samsung,exynos5433-cmu-top" - clock controller compatible for CMU_TOP
>> + which generates clocks for IMEM/FSYS/G3D/GSCL/HEVC/MSCL/G2D/MFC/PERIC/PERIS
>> + domains and bus clocks.
>> + - "samsung,exynos5433-cmu-cpif" - clock controller compatible for CMU_CPIF
>> + which generates clocks for LLI (Low Latency Interface) IP.
>> + - "samsung,exynos5433-cmu-mif" - clock controller compatible for CMU_MIF
>> + which generates clocks for DRAM Memory Controller domain.
>> + - "samsung,exynos5433-cmu-peric" - clock controller compatible for CMU_PERIC
>> + which generates clocks for UART/I2C/SPI/I2S/PCM/SPDIF/PWM/SLIMBUS IPs.
>> + - "samsung,exynos5433-cmu-peris" - clock controller compatible for CMU_PERIS
>> + which generates clocks for PMU/TMU/MCT/WDT/RTC/SECKEY/TZPC IPs.
>> + - "samsung,exynos5433-cmu-fsys" - clock controller compatible for CMU_FSYS
>> + which generates clocks for USB/UFS/SDMMC/TSI/PDMA IPs.
>> +
>> +- reg: physical base address of the controller and length of memory mapped
>> + region.
>> +
>> +- #clock-cells: should be 1.
>> +
>> +Each clock is assigned an identifier and client nodes can use this identifier
>> +to specify the clock which they consume.
>> +
>> +All available clocks are defined as preprocessor macros in
>> +dt-bindings/clock/exynos5433.h header and can be used in device
>> +tree sources.
>> +
>> +Example 1: Examples of clock controller nodes are listed below.
>> +
>> + cmu_top: clock-controller@...0030000 {
>> + compatible = "samsung,exynos5433-cmu-top";
>> + reg = <0x10030000 0x0c04>;
>> + #clock-cells = <1>;
>> + };
>> +
>> + cmu_cpif: clock-controller@...0fc0000 {
>> + compatible = "samsung,exynos5433-cmu-cpif";
>> + reg = <0x10fc0000 0x0c04>;
>> + #clock-cells = <1>;
>> + };
>> +
>> + cmu_mif: clock-controller@...05b0000 {
>> + compatible = "samsung,exynos5433-cmu-mif";
>> + reg = <0x105b0000 0x100c>;
>> + #clock-cells = <1>;
>> + };
>> +
>> + cmu_peric: clock-controller@...4c80000 {
>> + compatible = "samsung,exynos5433-cmu-peric";
>> + reg = <0x14c80000 0x0b08>;
>> + #clock-cells = <1>;
>> + };
>> +
>> + cmu_peris: clock-controller@...0040000 {
>> + compatible = "samsung,exynos5433-cmu-peris";
>> + reg = <0x10040000 0x0b20>;
>> + #clock-cells = <1>;
>> + };
>> +
>> + cmu_fsys: clock-controller@...56e0000 {
>> + compatible = "samsung,exynos5433-cmu-fsys";
>> + reg = <0x156e0000 0x0b04>;
>> + #clock-cells = <1>;
>> + };
>
> What are the reasons to split the whole clock controller into separate
> device nodes with different compatible strings like this? I doubt drivers
> associated with each of those compatible strings could be ever reused on
> different Exynos SoCs.
No special reason. I added the clock controller according to clock domain
separately. As I knew, samsung clk drivers use this way to support various
clock domains. For exmaple, drivers/clk/samsung/clk-exynos7.c.
>
> There are hardware dependencies between these clock domains, which are
> not currently modelled in DT with your binding.
Right. current samsung clock drivers cannot show the hierarchy among clock domains in DT.
IOW, there is currently
> no way to ensure proper registration order of the CMUs (clock domains).
> This may be important in some cases.
>
> To address this we could either add clocks/clock-names properties in
> respective CMU device nodes, pointing to any clocks in other CMU(s) or
> make a single device node for the whole clock controller, with an
> aggregated reg entry, e.g.
>
> cmu: clock-controller@...0030000 {
> compatible = "samsung,exynos5433-cmu";
> reg = <0x10030000 0x0c04>,
> <0x10fc0000 0x0c04>,
> <0x105b0000 0x100c>,
> <0x14c80000 0x0b08>,
> <0x10040000 0x0b20>,
> <0x156e0000 0x0b04>,
> ...
> reg-names = "top", "cpif", "mif", "peric", "peris", "fsys"...
> #clock-cells = <1>;
> };
If you make a single device node to support various clock domain,
How are you indicate the specific clock in some clock domain?
For example,
The serial dt node in exynos7.dtsi. serial_0 dt node use the uart clocks
in 'clock_peric0' clock domain and serial_1 dt node use the uart clocks
in 'clock-peric1' clock domain.
When using the clock in specific clock domain,
we need to phandle(e.g., clock_peric0, clock_peric1) of clock domain.
serial_0: serial@...30000 {
compatible = "samsung,exynos4210-uart";
reg = <0x13630000 0x100>;
interrupts = <0 440 0>;
clocks = <&clock_peric0 PCLK_UART0>,
<&clock_peric0 SCLK_UART0>;
clock-names = "uart", "clk_uart_baud0";
status = "disabled";
};
serial_1: serial@...20000 {
compatible = "samsung,exynos4210-uart";
reg = <0x14c20000 0x100>;
interrupts = <0 456 0>;
clocks = <&clock_peric1 PCLK_UART1>,
<&clock_peric1 SCLK_UART1>;
clock-names = "uart", "clk_uart_baud0";
status = "disabled";
};
>
> Then we could modify samsung_cmu_register_one() function by adding
> the reg entry index or name argument. What do you think ?
If there is more reasonable way to show the dependency between clock domains,
I will agree.
Best Regards,
Chanwoo Choi
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