[U-Boot] [PATCH] serial: ns16550: Add register shift variable

[Alexander Graf]

On 07/14/2018 05:49 PM, Tom Rini wrote:
> On Sat, Jul 14, 2018 at 12:47:21PM +0200, Wolfgang Denk wrote:
>> Dear Felix,
>>
>> In message <1531492980-16543-1-git-send-email-fb at ltec.ch> you wrote:
>>> The motivation for writing this patch originates in the
>>> effort of synchronizing U-Boot DT to Linux DT for am33xx SOCs.
>>> The current am33xx.dtsi file from U-Boot defines the <reg-shift>
>>> property for all UART nodes. The actual (4.18+) am33xx.dtsi
>>> file from Linux does not define <reg-shift> anymore. To prevent
>>> (probably difficult) changes in many .dts and .dtsi files once
>>> the synchronization is done, one can use this new variable. For
>>> the pdu001 board, for example, SYS_NS16550_REG_SHIFT is set
>>> to 2; no need to clutter U-Boot and board specific dts files
>>> with <reg-shift> properties.
>> Does this mean that U-Boot will not be able to use the same DTB as
>> Linux?
> To be clear, it's the other way around.  We can't use the Linux dtb/dts
> files as they've dropped (and in other cases, aren't adding) these
> properties as it's handled differently.

What does "differently" mean? Linux tries quite hard to be platform 
agnostic, so a per-build-target #define surely isn't what they're doing.

Are they inferring the shift from the compatible? In that case, we 
should do the same.


Alex