[PATCH 1/2] mmc: core: enable CMD19 tuning for DDR50 mode

Ulf Hansson ulf.hansson at linaro.org
Tue Aug 25 05:05:56 PDT 2015

On 20 August 2015 at 02:16, Barry Song <21cnbao at gmail.com> wrote:
> 2015-08-18 1:11 GMT+08:00 Ulf Hansson <ulf.hansson at linaro.org>:
>> On 11 August 2015 at 10:41, Barry Song <21cnbao at gmail.com> wrote:
>>> From: Weijun Yang <york.yang at csr.com>
>>> As SD Specifications Part1 Physical Layer Specification Version
>>> 3.01 says, CMD19 tuning is available for unlocked cards in transfer
>>> state of 1.8V signaling mode. The small difference between v3.00
>>> and 3.01 spec means that CMD19 tuning is also available for DDR50
>>> mode.
>> So what happens with cards following the 3.0 spec version, those
>> doesn't need to support the tuning CMD right? Perhaps that needs to be
>> addressed in this patch well!?
> from HW registers of the card, we cann't know whether the HW needs
> tuning. it is said 3.0.x need tuning, but 3.0 doesn't need.  @weijun,
> pls fix me if i am wrong.
> if so, it seems we need a static flag somewhere to indicate whether
> the tuning is needed. we can't detect to find the tuning requirement.

Another way is to always try doing the tuning for DDR50, but in case
of errors just ignore them and print a debug/info message!?

Kind regards

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