Re: [PATCH] sdhci-fujitsu: add support for setting the CMD_DAT_DELAY attribute

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2017-11-03 11:29 GMT+08:00 Vincent Yang <vincent.cw.yang@xxxxxxxxx>:
> 2017-11-02 19:00 GMT+08:00 Ulf Hansson <ulf.hansson@xxxxxxxxxx>:
>> + Vincent Yang (several emails, don't know which works)
>>
>> On 2 November 2017 at 11:49, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>>> On 2 November 2017 at 10:48, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>>>> On 2 November 2017 at 01:12, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>>>>> On 2 November 2017 at 00:08, Rob Herring <robh@xxxxxxxxxx> wrote:
>>>>>> On Wed, Nov 01, 2017 at 12:21:32AM +0000, Ard Biesheuvel wrote:
>>>>>>> The Socionext SynQuacer SoC inherits this IP from Fujitsu, but
>>>>>>> requires the F_SDH30_CMD_DAT_DELAY bit to be set in the
>>>>>>> F_SDH30_ESD_CONTROL control register.
>>>>>>>
>>>>>>> So let's add an optional property to this device's binding, and
>>>>>>> set the attribute if it is present in the DT node.
>>>>>>>
>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>>>>>>> ---
>>>>>>>  Documentation/devicetree/bindings/mmc/sdhci-fujitsu.txt |  2 ++
>>>>>>>  drivers/mmc/host/sdhci_f_sdh30.c                        | 18 +++++++++++++++++-
>>>>>>>  2 files changed, 19 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-fujitsu.txt b/Documentation/devicetree/bindings/mmc/sdhci-fujitsu.txt
>>>>>>> index de2c53cff4f1..9ad02f743ad0 100644
>>>>>>> --- a/Documentation/devicetree/bindings/mmc/sdhci-fujitsu.txt
>>>>>>> +++ b/Documentation/devicetree/bindings/mmc/sdhci-fujitsu.txt
>>>>>>> @@ -15,6 +15,8 @@ Required properties:
>>>>>>>  Optional properties:
>>>>>>>  - vqmmc-supply: phandle to the regulator device tree node, mentioned
>>>>>>>    as the VCCQ/VDD_IO supply in the eMMC/SD specs.
>>>>>>> +- cmd-dat-delay-select: boolean property indicating that this host requires
>>>>>>> +  the CMD_DAT_DELAY control to be enabled.
>>>>>>
>>>>>> Needs a vendor prefix unless this is a standard SDHCI bit (in which
>>>>>> case it should be documented in a common spot).
>>>>>>
>>>>>
>>>>> I suspect this is a non-standard thing, so I'll add the fujitsu prefix. Ulf?
>>>>
>>>> This is specific to the Fujitsu variant.
>>>>
>>>> However, what puzzles me is why this bit is needed for the Socionext
>>>> SynQuacer SoC, but not for other SoCs that uses this IP. That seems
>>>> weird (probably wrong).
>>>>
>>>> Moreover, the F_SDH30_CMD_DAT_DELAY register define is already there,
>>>> so I would rather suspect that it's something that did got fully
>>>> implemented. In other words, I don't think you need a new DT binding,
>>>> but rather try to implement it generically for the sdhci-f_sdh30
>>>> driver. Do you think that will work?
>>>>
>>>
>>> Do you mean set it unconditionally? That works for me, but I have no
>>
>> Yes.
>>
>>> way of testing whether it still works on other SoCs that use this IP.
>>
>> Me neither!
>
> Hi all, I can not yet get contact with IP owner because it is a
> holiday in Japan.
> Around two years ago, F_SDH30_CMD_DAT_DELAY was a new feature of this IP.
> I will update the latest information as soon as I get it.
>
I got a response from IP owner.
He explains F_SDH30_CMD_DAT_DELAY is intended to adjust signal timing of
CMD/DAT lines, and it is necessary to change its value according to
SoC/board design.
So he advises us to make F_SDH30_CMD_DAT_DELAY adjustable by a DT binding.

Kind regards
Vincent

>>
>> Apparently there are no DTS in the kernel git that uses the
>> "fujitsu,mb86s70-sdhci-3.0".
>
> Around two years ago, sdhci_f_sdh30_driver was a portion for mb86s70 SoC
> patch series, but finally the patch series did not fully go upstream.
>
> Kind regards
> Vincent
>
>>
>> I looped in Vincent Yang, let's hope he can provide us with some more
>> information.
>>
>> Kind regards
>> Uffe
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