From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3126C4727E for ; Thu, 1 Oct 2020 20:49:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 820D020738 for ; Thu, 1 Oct 2020 20:49:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727794AbgJAUtv (ORCPT ); Thu, 1 Oct 2020 16:49:51 -0400 Received: from gate.crashing.org ([63.228.1.57]:58748 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726581AbgJAUtv (ORCPT ); Thu, 1 Oct 2020 16:49:51 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 091KiIqu017242; Thu, 1 Oct 2020 15:44:19 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 091KiHHX017241; Thu, 1 Oct 2020 15:44:17 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 1 Oct 2020 15:44:17 -0500 From: Segher Boessenkool To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/6] powerpc/time: Rename mftbl() to mftb() Message-ID: <20201001204417.GP28786@gate.crashing.org> References: <94dc68d3d9ef9eb549796d4b938b6ba0305a049b.1601556145.git.christophe.leroy@csgroup.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <94dc68d3d9ef9eb549796d4b938b6ba0305a049b.1601556145.git.christophe.leroy@csgroup.eu> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 01, 2020 at 12:42:39PM +0000, Christophe Leroy wrote: > On PPC64, we have mftb(). > On PPC32, we have mftbl() and an #define mftb() mftbl(). > > mftb() and mftbl() are equivalent, their purpose is to read the > content of SPRN_TRBL, as returned by 'mftb' simplified instruction. > > binutils seems to define 'mftbl' instruction as an equivalent > of 'mftb'. > > However in both 32 bits and 64 bits documentation, only 'mftb' is > defined, and when performing a disassembly with objdump, the displayed > instruction is 'mftb' > > No need to have two ways to do the same thing with different > names, rename mftbl() to have only mftb(). There are mttbl and mttbu insns (and no mttb insn); they write a 32-bit half for the time base. There is an mftb, and an mftbu. mftbu reads the upper half, while mftb reads the *whole* register. SPR 269 is the TBU register, while SPR 268 is called both TB and TBL. Yes, it is confusing :-) The "mftb" name is much clearer than "mftbl" (on 64-bit), because it reads the whole 64-bit register. On 32-bit mftbl is clearer (but not defined in the architecture, not officially an insn or even an extended mnemonic). Segher