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

[Stefano Babic]

Hi Michael,

On 26/01/2018 23:14, Michael Nazzareno Trimarchi wrote:
> Hi Stefano
> 
> Do I need to resend with you in CC?
> 
> For some reason I forget to include you
> 

No, don't worry, I have already got it :-)

Regards,
Stefano

> Michael
> 
> On Fri, Jan 26, 2018 at 12:00 PM, Benoît Thébaudeau <benoit at wsystem.com> wrote:
>> 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
> 
> 
> 

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