Re: [PATCH v2 03/19] ARM: dts: Add DMC bus node for Exynos3250

Krzysztof Kozlowski
2015-12-10T01:20:24Z

On 10.12.2015 10:09, Chanwoo Choi wrote:
> On 2015년 12월 10일 09:44, Krzysztof Kozlowski wrote:
>> On 09.12.2015 13:07, Chanwoo Choi wrote:
>>> This patch adds the DMC (Dynamic Memory Controller) bus node for Exynos3250 SoC.
>>> The DMC is an AMBA AXI-compliant slave to interface external JEDEC standard
>>> SDRAM devices. The bus includes the OPP tables and the source clock for DMC
>>> block.
>>>
>>> Following list specifies the detailed relation between the clock and DMC block:
>>> - The source clock of DMC block : div_dmc
>>>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> ---
>>> arch/arm/boot/dts/exynos3250.dtsi | 34 ++++++++++++++++++++++++++++++++++
>>> 1 file changed, 34 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/exynos3250.dtsi b/arch/arm/boot/dts/exynos3250.dtsi
>>> index 2f30d632f1cc..7214c5e42150 100644
>>> --- a/arch/arm/boot/dts/exynos3250.dtsi
>>> +++ b/arch/arm/boot/dts/exynos3250.dtsi
>>> @@ -687,6 +687,40 @@
>>> clock-names = "ppmu";
>>> status = "disabled";
>>> };
>>> +
>>> + bus_dmc: bus_dmc {
>>> + compatible = "samsung,exynos-bus";
>>> + clocks = <&cmu_dmc CLK_DIV_DMC>;
>>> + clock-names = "bus";
>>> + operating-points-v2 = <&bus_dmc_opp_table>;
>>> + status = "disabled";
>>> + };
>>> +
>>> + bus_dmc_opp_table: opp_table1 {
>>
>> This is the firsy opp_table, right? So:
>> s/opp_table1/opp_table0/
>
> Right. It is first opp_table in exynos3250.dtsi.
> But, I'm considering the OPP table of CPU freqeuncy as opp_table0.
> So, I have the plan that support the operation-points-v2 for Exynos3250 CPU.

Ok

>
>>
>>> + compatible = "operating-points-v2";
>>> + opp-shared;
>>> +
>>> + opp00 {
>>> + opp-hz = /bits/ 64 <50000000>;
>>> + opp-microvolt = <800000>;
>>> + };
>>> + opp01 {
>>> + opp-hz = /bits/ 64 <100000000>;
>>> + opp-microvolt = <800000>;
>>> + };
>>> + opp02 {
>>> + opp-hz = /bits/ 64 <134000000>;
>>> + opp-microvolt = <800000>;
>>
>> Why 134, not 133 MHz?
>
> When I used the 133000000, the source clock is changed to 100Mhz instead of 133MHz.
> I add following test result on exynos3250-rinato board.
>
> Case1.
> When I use the 134 MHz, the source clock is changed to 133MHz
> : exynos-bus soc:bus_dmc: old_freq(200000000) -> new_freq (134000000) (real: 133333334)
>
> Case2.
> When I use the 133 MHz, the source clock is changed to 100MHz
> : exynos-bus soc:bus_dmc: old_freq(200000000) -> new_freq (133000000) (real: 100000000)

Now I remember that issue. You could use here directly 133333334 but
that also would look a little bit weird... so 134 is ok for me. Could
just add a comment that desired frequency is actually "133 MHz"?

Best regards,
Krzysztof