Hello Wolfgang, On 14.07.2018 12:47, 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? > This has already been answered very accurately by Tom. I have also written an RFC dealing with this: "[RFC] arm: dts: am33xx: Sync DTS with Linux 4.16.11", posted May 24.
>> +config SYS_NS16550_REG_SHIFT >> + int "Number of bytes to shift register offsets" >> + default 0 >> + depends on SYS_NS16550 >> + help >> + Use this to specify the amount of bytes between discrete >> + device registers. If, for example, the device registers are >> + located at 0x00, 0x04, 0x08, 0x0C and so forth than set >> + this to 2. The default value is 0. > > This description is inconsistent or misleading. How do you define > "space between registers"? The unused gaps? In the example, the > registers are spaced at 4 bytes intervals, so a value of 2 would > only make sense of we have 16 bit registters and you count the gap > bytes. > > But this is a very strange and uncommon way to describe such a > situation, especially when you write that you "shift register > offsets". Here I think about something like a LSL operation, so > shifing by 2 bits would result in a 2^2 = 4 byte spacing. > > This needs to be rewritten. > You are right, sorry. It seems I used my brain to mix up two different explanations and that's the result - will be fixed. > > Best regards, > > Wolfgang Denk > regards, Felix _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
