On Tue, Sep 20, 2016 at 10:45 AM, jonsm...@gmail.com <jonsm...@gmail.com> wrote:
> On Tue, Sep 20, 2016 at 10:10 AM, TsvetanUsunov <tsvetanusu...@gmail.com> 
> wrote:
>>
>>
>> понеделник, 19 септември 2016 г., 20:06:13 UTC+3, Hans de Goede написа:
>>>
>>> Hi,
>>>
>>> On 19-09-16 18:07, TsvetanUsunov wrote:
>>> > Hi,
>>> >
>>> > We make our final touch of A64-OLinuXino PCB and there we add option
>>> > eMMC Flash to work on dual voltages 1.8V and 3.3V.
>>> > The eMMC is connected to AXP803 pin.34 GPIO1/LDO. The problem is that
>>> > when A64 boots and AXP803 is not initialized it outputs default 0.8V then
>>> > after initialization driver takes care to drive it  1.8V or 3.3V.
>>> > This makes impossible to boot from eMMC which is not good. We now think
>>> > for solution which to drive eMMC at 3.3V initially when AXP803 output is
>>> > below 1.8V but this adds unnecessary hardware complexity.
>>> > For hardware point of view it will be much more simplier if dedigated
>>> > A64 GPIO is used and initially is pulled down and after AXP803 is
>>> > initialized is pulled up.
>>>
>>> Ok, so what your suggesting is:
>>>
>>> axp803-ldo-io1  -\
>>>                    [mux]---> mmc-supply
>>> Fixed-3.3v ------/  |
>>>                      |
>>>                      |mux-control
>>> A64 gpio out--------/
>>>
>>> Note the above ascii-art requires a fixed-width font.
>>>
>>> With a pull-down (or pull-up) to fix the mux in a certain position when
>>> the gpio is in tri-state ?
>>>
>>> As long as we pin the axp803-ldo-io1 at 1.8v then the Linux regulator
>>> framework should be able to deal with, and in u-boot we can just
>>> keep things at 3.3v.
>>>
>>> > How would you suggest us to implement it? Will this additional GPIO
>>> > create troubles in eMMC driver philosophy?
>>>
>>> For the Linux mmc driver the mmc-supply is abstracted as a regulator,
>>> and the regulator framework should be able to deal with any setup
>>> you can come up with.
>>>
>>> > For the SDMMC we are still hesitating what to do as we don't know if the
>>> > card which will be inserted will support low voltage and higher speeds at
>>> > all.
>>>
>>> As long as you default to 3.3v then the kernel's sd subsystem can
>>> dynamically switch voltage (through e.g. the gpio) if the card
>>> advertises it supports low voltage. Note that you're planning
>>> the first board to implement this that I know off, so the sunxi-mmc
>>> kernel driver will need some work to support voltage switching,
>>> but in the mean time things should work fine at 3.3v.
>>>
>>> > Also eMMC Flash and SDMMC card should be driven by separate voltages, as
>>> > they may work in any combinations.
>>>
>>> Ack, right, as said both cards should come up with 3.3v and then
>>> a new voltage will be negotiated before switching, so this definitely
>>> needs to be per card.
>>>
>>> > This means we need another AXP803 LDO and another GPIO for the SDMMC
>>> > card.
>>>
>>> Right
>>
>>
>> Micron eMMC chips we use do not support higher clock at lower voltage, so
>> the way we wired the schematic right now makes no much sense.
>> I check for other vendors but also can't find such eMMC chip, if someone
>> knows please let us know to investigate more?
>>
>> So in this case makes sense to move the dual voltage supply to the SD-MMC
>> card only but this rise some more issues :)
>>
>> The card is currently wired to port F which Vcc is internally connected
>> together with port B and H where is WiFi SIDO , I2C UARTs etc which will be
>> lost if we power with 1.8V, so no go.
>>
>> We can swap the SD-MMC and eMMC ports, port F and port C, but in this case
>> we will lose the NAND Flash option i.e. the possibility to run Android.
>>
>> I still can't find SD-MMC card which to work on 1.8 and 3.3V can you point
>> me to some model so we perform test and see if this is really good to have
>> feature, or we will cut this and wire 3.3V permanently :)
>
> I have not tried low voltage SD Cards but...
>
> Here is a chart of the UHS modes
> http://panasonic.net/avc/sdcard/industrial_sd/performance.html
>
> Here are UHS SD Cards for sale:
> http://www.lexar.com/products.html
>
> I was unaware of 0.4V UHS-II, but Lexar is selling UHS-II cards. Don't
> know what supply voltage they need.
>
> -------------------------------------------------------
>
> For eMMC I believe you are looking for:
> eMMC 4.5 HS200
> eMMC 5.0 HS400

A64 only has a eMMC 4.5 controller so forget about HS400.


>
> Kingston sells these, I think Samsung does too.
> http://www.kingston.com/us/embedded/emmc
>
> They come in wide temp
> https://media.kingston.com/pdfs/emmc/i_temp_eMMC_Product_Flyer.pdf
>
> About $5 for 4GB from US distributors, so probably $3 from Chinese one.
> Random check of similar Kingston part from Chinese supplier - $3.38
>
> Support for HS200/HS400 is already in kernel so someone is using it.
>
>>
>> Tsvetan
>>
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>
>
>
> --
> Jon Smirl
> jonsm...@gmail.com



-- 
Jon Smirl
jonsm...@gmail.com

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