Hello Alexey, On 16.07.2018 17:04, Alexey Brodkin wrote: > Hi Felix, > >> -----Original Message----- >> From: Felix Brack [mailto:[email protected]] >> Sent: Sunday, July 15, 2018 5:02 PM >> To: Alexey Brodkin <[email protected]>; Tom Rini >> <[email protected]> >> Cc: [email protected]; Stefan Roese <[email protected]>; Alexander Graf >> <[email protected]>; Michal Simek <[email protected]>; >> Wolfgang Denk <[email protected]> >> Subject: Re: [U-Boot] [PATCH] serial: ns16550: Add register shift variable >> >> Hi Alexey, >> >> On 15.07.2018 10:43, Alexey Brodkin wrote: >>> Hi Tom, Felix, all >>> >>>> -----Original Message----- >>>> From: Tom Rini [mailto:[email protected]] >>>> Sent: Saturday, July 14, 2018 6:50 PM >>>> To: Wolfgang Denk <[email protected]> >>>> Cc: Felix Brack <[email protected]>; [email protected]; Stefan Roese >>>> <[email protected]>; Alexey Brodkin <[email protected]>; >>>> Alexander Graf <[email protected]>; Michal Simek <[email protected]> >>>> Subject: Re: [U-Boot] [PATCH] serial: ns16550: Add register shift variable >>>> >>>> On Sat, Jul 14, 2018 at 12:47:21PM +0200, Wolfgang Denk wrote: >>>>> Dear Felix, >>>>> >>>>> In message <[email protected]> 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. >>> >>> 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? > I think there is nothing wrong with the kernel's .dtsi files, hence nothing to be fixed in Linux. Please read the RFC I posted May 24. It (hopefully) explains the need of this patch. In short: syncing U-Boot DT files for AM33xx SoC with Linux DT files will break things. This patch would fix the problem of the "missing <reg-shift>" property.
regards Felix _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
