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

[Michael Nazzareno Trimarchi]

Hi

On Thu, Jan 25, 2018 at 10:48 PM, Benoît Thébaudeau
<benoit.thebaudeau.dev at gmail.com> wrote:
> Hi Michael,
>
> 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

I will repost. On my side I have tested already some of the
peripherals you mention
but I was not having the second slod for eSDHC.

We already run preliminary testing on the hardware and usb problem is right now
fixed.

Thank you for testing

Michael

> 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).
>
> If the bus-status detection example in the documentation of SION in
> the reference manual is useful, it means that SION is probably
> required for all the signals requiring simultaneous output and input
> (such as I²C for device clock stretching or multi-master bus
> arbitration, except if the IP toggles between input and output low at
> each clock edge rather than between open-drain output high and output
> low), because there are no automatic SION signals between the
> peripherals and the pads but only direction signals that can request a
> single direction at a time. For bidirectional signals that do not
> require simultaneous output and input because they work in turns (such
> as FEC MDIO), SION can be required or not depending on whether the IP
> toggles the direction signal for each turn or always expects an input
> feedback while driving an open-drain output high. Even if SION is
> required for the I²C example mentioned above (which is unlikely as
> basic I²C transfers work fine and clock stretching detection is
> automatic and would always need the input state), the need for these
> advanced I²C features can be considered board-specific, so SION would
> still not be required in iomux-mx25.h.
>
> In the end, for this patch, apart from the pending test for FEC MDIO:
> Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau.dev at gmail.com>
>
> Best regards,
> Benoît



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