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

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

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