[U-Boot] [PATCH] mx6: Avoid writing to read-only bits in imximage.cfg

[Marek Vasut <marex@denx.de>]

Dear Liu Hui-R64343,

[...]

> >> >> According to REV C manual, the register IOMUXC_IOMUXC_GPR4 has bits
> >> >> 4 and 5 read-only and the value is always set as zero.
> >> >> So write '0' to these bits instead of writing '1'.
> >> >
> >> >Jason, Fabio: What do you think? You should be the datasheet
> >> >'masters' ;)
> >> 
> >> Yes, according to the RM,
> >> 5
> >> Reserved
> >> This read-only field is reserved and always has the value 0.
> >> 4
> >> Reserved
> >> This read-only field is reserved and always has the value 0.
> >> 
> >> So, write 1 should have no effect.
> >
> >I really dislike how "write 1 should have no effect" sounds. Can you
> >please check with HW people?
> 
> Since this is read-only bit, if you write 1 to it, it will have no effect.

For how long do you work with hardware? Did it never occur to you that when you 
wrote 1 to an "reserved" bit, it either did something you didn't expect or you 
had to rework it later because the new CPU has that bit for something else?

> Yes, to avoid the confusion, for example to do the read-back check, I agree
> with not writing '1' to the read-only bit.

Please, ask the hardware people about this.

> >[..]
> >
> >Best regards,
> >Marek Vasut

Best regards,
Marek Vasut