On 11/15/2016 09:48 AM, Shawn Lin wrote:
> On 2016/11/14 18:04, Jaehoon Chung wrote:
>> On 11/14/2016 07:00 PM, Jun Nie wrote:
>>> 2016-11-14 15:58 GMT+08:00 Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>:
>>>> On 2016/11/8 9:24, Jun Nie wrote:
>>>>>
>>>>> Document the device-tree binding of ZTE MMC host on
>>>>> ZX296718 SoC.
>>>>>
>>>>> Signed-off-by: Jun Nie <jun.nie@xxxxxxxxxx>
>>>>> ---
>>>>> .../devicetree/bindings/mmc/zx-dw-mshc.txt | 35
>>>>> ++++++++++++++++++++++
>>>>> 1 file changed, 35 insertions(+)
>>>>> create mode 100644 Documentation/devicetree/bindings/mmc/zx-dw-mshc.txt
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/mmc/zx-dw-mshc.txt
>>>>> b/Documentation/devicetree/bindings/mmc/zx-dw-mshc.txt
>>>>> new file mode 100644
>>>>> index 0000000..c175c4b
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/mmc/zx-dw-mshc.txt
>>>>> @@ -0,0 +1,35 @@
>>>>> +* ZTE specific extensions to the Synopsys Designware Mobile Storage
>>>>> + Host Controller
>>>>> +
>>>>> +The Synopsys designware mobile storage host controller is used to
>>>>> interface
>>>>> +a SoC with storage medium such as eMMC or SD/MMC cards. This file
>>>>> documents
>>>>> +differences between the core Synopsys dw mshc controller properties
>>>>> described
>>>>> +by synopsys-dw-mshc.txt and the properties used by the ZTE specific
>>>>> +extensions to the Synopsys Designware Mobile Storage Host Controller.
>>>>> +
>>>>> +Required Properties:
>>>>> +
>>>>> +* compatible: should be
>>>>> + - "zte,zx296718-dw-mshc": for ZX SoCs
>>>>> +
>>>>> +Example:
>>>>> +
>>>>> + mmc1: mmc@1110000 {
>>>>> + compatible = "zte,zx296718-dw-mshc";
>>>>> + #address-cells = <1>;
>>>>> + #size-cells = <0>;
>>>>> + reg = <0x01110000 0x1000>;
>>>>> + interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>;
>>>>> + fifo-depth = <32>;
>>>>> + data-addr = <0x200>;
>>>>> + fifo-watermark-aligned;
>>>>> + bus-width = <4>;
>>>>> + clock-frequency = <50000000>;
>>>>
>>>>
>>>> do you need both clock-frequency and max-frequency here?
>>>
>>> According to dts document, clock-frequency is for clock configuration
>>> when dw core probe. max-frequency is for mmc core to limit max
>>> frequency for any cards at any time. Do you have any suggestion? Thank
>>> you for your time!
>>
>> As i know, Jun's comment is right. :)
>> clock-frequency should be used with clk_set_rate().
>
> yup, I was thinking that should we reuse max-frequency instead of
> clock-frequency in the future? I saw most of the DT(I didn't check all
> of them) assign clock-frequency to the same value as max of clock-
> freq-min-max. I think it's pointless if the clock-frequency is different
> from max-frequency as both of them will be setted via dw_mmc and finally
> we only take min(clock-frequency, max-frquency). Was I missing
> something?
Well, clock-frequency is for setting CMU. but max-frequency is not really used for CMU.
For example, clock-frequency is 100MHz. Max-frequency is 50MHz.
It's possible to use. then dwmmc controller should divide to 2 for max-frequency.
There are too many cases. Source clock can be 400MHz or 200MHz..etc..
but maximum clock is decided according to busmode.
I'm not sure because i didn't have HW knowledge..
but in my experience,
1) 400MHz/2 = 200MHz,
2) 800MHz/4 = 200MHz.
1) and 2) are same value as 200MHz. but those clock phase might be a little difference.
So i want to keep the clock-frequency for setting the initial CMU value.
What your opinion? :)
Best Regards,
Jaehoon Chung
>
> What is your opinion, Jaehoon and Jun? :)
>
>>
>>>
>>>>
>>>>> + clocks = <&topcrm SD0_AHB>, <&topcrm SD0_WCLK>;
>>>>> + clock-names = "biu", "ciu";
>>>>> + num-slots = <1>;
>>>>> + max-frequency = <50000000>;
>>>>> + cap-sdio-irq;
>>>>> + cap-sd-highspeed;
>>>>> + status = "disabled";
>>>>> + };
>>>>>
>>>>
>>>>
>>>> --
>>>> Best Regards
>>>> Shawn Lin
>>>>
>>>
>>>
>>>
>>
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>
>
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