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

[Liu Hui-R64343]

Hi, Marek,

>-----Original Message-----
>From: Marek Vasut [mailto:marex at denx.de]
>Sent: Wednesday, June 13, 2012 7:18 PM
>To: u-boot at lists.denx.de
>Cc: Liu Hui-R64343; Dirk Behme; Fabio Estevam
>Subject: Re: [U-Boot] [PATCH] mx6: Avoid writing to read-only bits in
>imximage.cfg
>
>Dear Liu Hui-R64343,
>
>> >-----Original Message-----
>> >From: Dirk Behme [mailto:dirk.behme at de.bosch.com]
>> >Sent: Tuesday, June 12, 2012 11:05 PM
>> >To: Fabio Estevam; Liu Hui-R64343
>> >Cc: Vikram Narayanan; u-boot at lists.denx.de
>> >Subject: Re: [U-Boot] [PATCH] mx6: Avoid writing to read-only bits in
>> >imximage.cfg
>> >
>> >On 12.06.2012 16:50, Vikram Narayanan wrote:
>> >> If in case this is valid according to the latest datasheet, ignore
>> >> this patch.
>> >>
>> >> --
>> >> 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.

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

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