From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from buildserver.ru.mvista.com (unknown [85.21.88.6]) by ozlabs.org (Postfix) with ESMTP id AED01DDED7 for ; Tue, 25 Mar 2008 03:14:30 +1100 (EST) Message-ID: <47E7D3BB.1050403@ru.mvista.com> Date: Mon, 24 Mar 2008 19:15:55 +0300 From: Sergei Shtylyov MIME-Version: 1.0 To: Grant Likely Subject: Re: [PATCH 2/3] [POWERPC] Xilinx: of_serial support for Xilinx uart 16550. References: <12060242324116-git-send-email-john.linn@xilinx.com> <20080320144402.3063517C005D@mail148-sin.bigfish.com> <18403.32257.725539.470771@cargo.ozlabs.ibm.com> <47E7B61B.70708@ru.mvista.com> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Cc: linuxppc-dev@ozlabs.org, Paul Mackerras , John Linn List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Grant Likely wrote: >> >> > Personally, I'm not fond of this approach. There is already some >> >> > traction to using the reg-shift property to specify spacing, and I >> >> > think it would be appropriate to also define a reg-offset property to >> >> > handle the +3 offset and then let the xilinx 16550 nodes use those. >> >> Why do we need a reg-offset property when we can just add the offset >> >> to the appropriate word(s) in the reg property? > >> > Primarily because the device creates 32 byte registers starting at 0; >> > but they are also big-endian byte accessible so a byte read at offset >> > 8 also works. >> Probably I misunderstood you: does it give the same result as offset 11? > er; typo; oops. A 32 bit read add offset 0 is the same as a byte read > at offset *3*. Oh, well... unfortunately, we can't use UPIO_MEM32 "register model" in 8250.c anyway since that makes use of readl()/writel() -- which treat the bus as bigendian on PPC... anyway, we would need at least a "reg-size" property, if not new "compatible"... >> > reg-offset seems to be a better description of the hardware to me. >> Have you considered using the existing "big-endian" property? > No I haven't, but that would work too. I'm happy with that if it > works for you. If the property was defined, then the byte offset to > the first reg would be adjusted by 1^(reg-shift) - 1 You don't mean "xor" by ^, do you? :-O In fact, it should be <<... > Cheers, > g. WBR, Sergei