[U-Boot] [PATCH V3] imx: mx25: Remove SION bit in all pin-mux that are safe

[Benoît Thébaudeau]

On 25/01/2018 at 22:48, Benoît Thébaudeau wrote:
> On Thu, Jan 25, 2018 at 2:06 PM, Michael Trimarchi
> <michael at amarulasolutions.com> wrote:
>> SION bit should be used in the situation that we need
>> to read back the value of a pin and should not be set by
>> default macro.
>>
>> We get some malfunction as raised by following thread
>>
>> https://www.spinics.net/lists/linux-usb/msg162574.html
>>
>> As reported by this application note:
>> https://www.nxp.com/docs/en/application-note/AN5078.pdf
>>
>> The software input on (SION) bit is an option to force an input
>> path to be active regardless of the value driven by the
>> corresponding module. It is used when the nature direction
>> of a pin depending on selected alternative function is an output,
>> but it is needed to read the real logic value on a pin.
>>
>> The SION bit can be used in:
>> • Loopback: the module of a selected alternative function drives
>> the pad and also receives the pad value as an input
>> • GPIO capture: the module of a selected alternative function
>> drives the pin and the value is captured by the GPIO
>>
>> SION bit is not necessary when the pin is configured as a peripheral
>> apart specific silicon bug. If an application needs to have this
>> set, this should be done in board file or in dts file
>>
>> Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> 
> [...]
> 
> I have now tested the following peripherals on i.MX25 without any SION
> bit set: AUDMUX/SSI, eSDHC, FEC (except PHY access for which MDIO
> might have an issue without SION; Ethernet works but I have not
> checked whether this is possible at least partially without access to
> the PHY registers), GPIO, I2C, SLCDC, UART, and USB. Everything worked
> fine except the lack of SION for eSDHC CMD, which is true for all
> eSDHC instances (and not only for eSDHC1, so Linux's
> arch/arm/boot/dts/imx25-pinfunc.h should be fixed). Therefore, SION is
> mandatory for all the eSDHC CMD functions in
> arch/arm/include/asm/arch-mx25/iomux-mx25.h, but it can be removed for
> everything else (I still have to carry out one more test to confirm
> this for FEC MDIO), and moved to the board files if necessary (but I
> don't think that any mainline board code is doing something fancy
> enough to need it).

I confirm that FEC RMII register access works fine without setting SION for
MDIO.

Benoît