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

[Tom Rini]

On Mon, Jul 16, 2018 at 06:47:21PM +0300, Andy Shevchenko wrote:
> On Mon, Jul 16, 2018 at 6:04 PM, Alexey Brodkin
> <Alexey.Brodkin at synopsys.com> wrote:
> 
> >> > Any chance to get a reference to the commit in Linux kernel that introduces that change?
> >> >
> >> In fact I believe that the <reg-shift> property never existed in the
> >> am33xx.dtsi file from Linux. U-Boot commit 85cf0e6299 shows that the
> >> property has been added to U-Boot's am33xx.dtsi file. The commit log
> >> clearly states why this happened:
> >>
> >> "With the commit 'c7b9686d5d48 ("ns16550: unify serial_omap")' all
> >> TI platforms are broken with DM/DT boot as ns16550 driver expects
> >> reg-shift from DT which is not populated for TI platforms.
> >> Earlier it worked as it was hard coded to 2 in serial-omap
> >> driver. So adding the reg-shift to serial nodes for dra7, am4372
> >> and am33xx dtsi files. Tested this patch on am437x-sk-evm,
> >> am437x-gp-evm, am335x-boneblack, dra74x-evm and dra72x-evm."
> >
> > Ok so this has nothing to do with changes in Linux kernel I guess.
> > Why don't we go the other way around and not just submit
> > a change to .dts files in Linux kernel that are missing required properties?
> 
> You may change DTSi files in the Linux kernel sources tree, but you
> wouldn't be able to fix all DTB:s in the wild.
> In this case Linux should have a fallback to the previous value in
> case property is not found.

No, we don't allow for U-Boot to be run with an arbitrary "wild" DTB
file nor the same DTB as the kernel (the kernel could run with a subset
of our DTB however).

-- 
Tom
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