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GET /api/patches/1629764/?format=api
{ "id": 1629764, "url": "http://patchwork.ozlabs.org/api/patches/1629764/?format=api", "web_url": "http://patchwork.ozlabs.org/project/uboot/patch/20220511183727.1834-1-pali@kernel.org/", "project": { "id": 18, "url": "http://patchwork.ozlabs.org/api/projects/18/?format=api", "name": "U-Boot", "link_name": "uboot", "list_id": "u-boot.lists.denx.de", "list_email": "u-boot@lists.denx.de", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20220511183727.1834-1-pali@kernel.org>", "list_archive_url": null, "date": "2022-05-11T18:37:27", "name": "powerpc: mpc85xx: Simplify jump to _start_cont in flash code", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": false, "hash": "acf8cd1e3c8816c1efe4b129cb00b37927e31287", "submitter": { "id": 78810, "url": "http://patchwork.ozlabs.org/api/people/78810/?format=api", "name": "Pali Rohár", "email": "pali@kernel.org" }, "delegate": { "id": 55230, "url": "http://patchwork.ozlabs.org/api/users/55230/?format=api", "username": "freenix", "first_name": "Peng", "last_name": "Fan", "email": "van.freenix@gmail.com" }, "mbox": "http://patchwork.ozlabs.org/project/uboot/patch/20220511183727.1834-1-pali@kernel.org/mbox/", "series": [ { "id": 299712, "url": "http://patchwork.ozlabs.org/api/series/299712/?format=api", "web_url": "http://patchwork.ozlabs.org/project/uboot/list/?series=299712", "date": "2022-05-11T18:37:27", "name": "powerpc: mpc85xx: Simplify jump to _start_cont in flash code", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/299712/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/1629764/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/1629764/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<u-boot-bounces@lists.denx.de>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@bilbo.ozlabs.org", "Authentication-Results": [ "bilbo.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=TEUcLHOP;\n\tdkim-atps=neutral", "ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.denx.de\n (client-ip=2a01:238:438b:c500:173d:9f52:ddab:ee01; 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Wed, 11 May 2022 22:54:25 +0200 (CEST)", "from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75])\n (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))\n (No client certificate requested)\n by phobos.denx.de (Postfix) with ESMTPS id 1AE108435A\n for <u-boot@lists.denx.de>; Wed, 11 May 2022 22:54:23 +0200 (CEST)", "from smtp.kernel.org (relay.kernel.org [52.25.139.140])\n (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))\n (No client certificate requested)\n by ams.source.kernel.org (Postfix) with ESMTPS id A8AA7B825C9\n for <u-boot@lists.denx.de>; Wed, 11 May 2022 20:54:22 +0000 (UTC)", "by smtp.kernel.org (Postfix) with ESMTPSA id 33BE7C34115\n for <u-boot@lists.denx.de>; Wed, 11 May 2022 20:54:21 +0000 (UTC)", "by pali.im (Postfix)\n id 42FA721A6; Wed, 11 May 2022 22:54:18 +0200 (CEST)", "by pali.im (Postfix)\n id B9DA721A6; Wed, 11 May 2022 20:37:32 +0200 (CEST)" ], "X-Spam-Checker-Version": "SpamAssassin 3.4.2 (2018-09-13) on phobos.denx.de", "X-Spam-Level": "", "X-Spam-Status": "No, score=-2.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,\n DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,\n SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no\n version=3.4.2", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n s=k20201202; t=1652302461;\n bh=mjaPSaRBFbVGIl+q/r/HRZ/JKip7nTefl/PW/1mouZY=;\n h=Resent-From:Resent-Date:Resent-To:From:To:Cc:Subject:Date:From;\n b=TEUcLHOPDRCJOMMoVXe4aI7ITahcUPd5byr1roefWUVnMUqEqoasDIWb0Qm+OzD72\n 06XmbwjV1cReyAxynK1qD7tIIBc2dOkzTzsHV+vbG7WFo5WieqxwHYg7rVqC84xbe9\n cGahRk+Vj/mWgWFtSD0rJQPvUDYSEjsDp2K8+IfzBCOPl4qVR2MR+ZZ6JjCmsuKZ7O\n Eaq9HuxJsJPnmC3vLNqQ3WvzkLBrgpETiIyZ9SL15frjh832jC7Vp5moy0x92HgGRU\n TQJjOnwtQzUJ0Hi7RQgiruOdMo5gfxYaei9ru6rXpRKiUcEMP8Ml3ayI+G8WH5kQIC\n 3remjYpVb+f9Q==", "Resent-From": "Pali =?utf-8?b?Um9ow6Fy?= <pali@kernel.org>", "Resent-Date": "Wed, 11 May 2022 22:54:18 +0200", "Resent-Message-ID": "<20220511205418.weie4gehca7az5cr@pali>", "Resent-To": "u-boot@lists.denx.de", "From": "=?utf-8?q?Pali_Roh=C3=A1r?= <pali@kernel.org>", "To": "Priyanka Jain <priyanka.jain@nxp.com>, Wolfgang Denk <wd@denx.de>,\n Sinan Akman <sinan@writeme.com>", "Cc": "u-boot@lists.denx.de", "Subject": "[PATCH] powerpc: mpc85xx: Simplify jump to _start_cont in flash code", "Date": "Wed, 11 May 2022 20:37:27 +0200", "Message-Id": "<20220511183727.1834-1-pali@kernel.org>", "X-Mailer": "git-send-email 2.20.1", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=UTF-8", "Content-Transfer-Encoding": "8bit", "X-BeenThere": "u-boot@lists.denx.de", "X-Mailman-Version": "2.1.39", "Precedence": "list", "List-Id": "U-Boot discussion <u-boot.lists.denx.de>", "List-Unsubscribe": "<https://lists.denx.de/options/u-boot>,\n <mailto:u-boot-request@lists.denx.de?subject=unsubscribe>", "List-Archive": "<https://lists.denx.de/pipermail/u-boot/>", "List-Post": "<mailto:u-boot@lists.denx.de>", "List-Help": "<mailto:u-boot-request@lists.denx.de?subject=help>", "List-Subscribe": "<https://lists.denx.de/listinfo/u-boot>,\n <mailto:u-boot-request@lists.denx.de?subject=subscribe>", "Errors-To": "u-boot-bounces@lists.denx.de", "Sender": "\"U-Boot\" <u-boot-bounces@lists.denx.de>", "X-Virus-Scanned": "clamav-milter 0.103.5 at phobos.denx.de", "X-Virus-Status": "Clean" }, "content": "After more patches code for jumping to _start_cont symbol in flash memory\ninvolved to code with useless mathematical operations. Currently it does:\n\n r3 := CONFIG_SYS_MONITOR_BASE + ABS(_start_cont) - CONFIG_SYS_MONITOR_BASE\n jump to r3\n\nWhich is equivalent of just:\n\n r3 := ABS(_start_cont)\n jump to r3\n\nThe purpose of that code is just to jump to _start_code symbol,\nindependently of program counter. So branch must be done to absolute\naddress. Trying to write:\n\n ba _start_cont\n\njust cause linker error:\n\n LD u-boot\n powerpc-linux-gnuspe-ld.bfd: arch/powerpc/cpu/mpc85xx/start.o: in function `switch_as':\n (.bootpg+0x4b8): relocation truncated to fit: R_PPC_ADDR24 against symbol `_start_cont' defined in .text section in arch/powerpc/cpu/mpc85xx/start.o\n make: *** [Makefile:1801: u-boot] Error 1\n\nProbably by the fact that absolute address cannot be expressed by 24-bits.\nSo write the code via mtlr+blr pattern as it was before and load general\npurpose register with absolute address of the symbol:\n\n lis r3,_start_cont@h\n ori r3,r3,_start_cont@l\n mtlr r3\n blr\n\nSeems that gcc and gnu ld linker support symbol@h and symbol@l syntax like\nnumber@h and number@l without any problem. And disassembling of compiler\nu-boot binary proved that lis+ori instructions are called with numbers\nwhich represent halves of absolute address of _start_cont symbol.\n\nSigned-off-by: Pali Rohár <pali@kernel.org>\n---\n arch/powerpc/cpu/mpc85xx/start.S | 5 ++---\n 1 file changed, 2 insertions(+), 3 deletions(-)", "diff": "diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S\nindex 50b23a97662c..6e3900e7923b 100644\n--- a/arch/powerpc/cpu/mpc85xx/start.S\n+++ b/arch/powerpc/cpu/mpc85xx/start.S\n@@ -1211,9 +1211,8 @@ switch_as:\n #else\n \t/* Calculate absolute address in FLASH and jump there\t\t*/\n \t/*--------------------------------------------------------------*/\n-\tlis\tr3,CONFIG_SYS_MONITOR_BASE@h\n-\tori\tr3,r3,CONFIG_SYS_MONITOR_BASE@l\n-\taddi\tr3,r3,_start_cont - CONFIG_SYS_MONITOR_BASE\n+\tlis\tr3,_start_cont@h\n+\tori\tr3,r3,_start_cont@l\n \tmtlr\tr3\n \tblr\n #endif\n", "prefixes": [] }