From patchwork Tue Sep 3 09:32:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 11127509 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C1CB61398 for ; Tue, 3 Sep 2019 09:34:05 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9FADD22CF8 for ; Tue, 3 Sep 2019 09:34:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="G1zMIkWS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FADD22CF8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+patchwork-linux-riscv=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1TyGUDvzRqIe/OBKDNNrWiDwUXPsKBlKZo78tXynUhQ=; b=G1zMIkWS+BY7Mg H+OkUlomtzFS1eGuy/6rSnO1MkxMKFka4Z2JkEUhRdn+lMWrE+803u7TEDq1xCBTMp9VKS14Y+1G3 LFP1qz3xgFu1Kx5j5mqPgWhqRQk/+e+MiMBcc4zmsCKUY0TvmDxH7NBn+iftg9vsIFqdF3AP+8sSn LUAkWOxsuPGtpm5Aaje5EHZEw+ayxP/OkD2epW5UDpLEvpAuBRur4/a6tmJwotF3iTBFZGO5HAKmK qCyMl+q7EUyu6RBQzlL1zfQZf/1liQEnx2j/prFCaWNLwev5tfhhXRhS/+gRXM1pW8b4bWev6xTR8 Ri6lUqTiYUqU01PWfSvA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i55CL-0005QX-0V; Tue, 03 Sep 2019 09:34:01 +0000 Received: from clnet-p19-102.ikbnet.co.at ([83.175.77.102] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1i55Bf-0004nW-1q; Tue, 03 Sep 2019 09:33:19 +0000 From: Christoph Hellwig To: Palmer Dabbelt , Paul Walmsley Subject: [PATCH 15/20] riscv: read the hart ID from mhartid on boot Date: Tue, 3 Sep 2019 11:32:34 +0200 Message-Id: <20190903093239.21278-16-hch@lst.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190903093239.21278-1-hch@lst.de> References: <20190903093239.21278-1-hch@lst.de> MIME-Version: 1.0 X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Atish Patra , Damien Le Moal , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Sender: "linux-riscv" Errors-To: linux-riscv-bounces+patchwork-linux-riscv=patchwork.kernel.org@lists.infradead.org From: Damien Le Moal When in M-Mode, we can use the mhartid CSR to get the ID of the running HART. Doing so, direct M-Mode boot without firmware is possible. Signed-off-by: Damien Le Moal Signed-off-by: Christoph Hellwig Reviewed-by: Atish Patra --- arch/riscv/include/asm/csr.h | 1 + arch/riscv/kernel/head.S | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h index 0dae5c361f29..d0b5113e1a54 100644 --- a/arch/riscv/include/asm/csr.h +++ b/arch/riscv/include/asm/csr.h @@ -81,6 +81,7 @@ #define SIE_SEIE (_AC(0x1, UL) << IRQ_S_EXT) /* symbolic CSR names: */ +#define CSR_MHARTID 0xf14 #define CSR_MSTATUS 0x300 #define CSR_MIE 0x304 #define CSR_MTVEC 0x305 diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index bb96bb7b95d2..e0350499d7a4 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -50,6 +50,14 @@ _start_kernel: csrw CSR_XIE, zero csrw CSR_XIP, zero +#ifdef CONFIG_RISCV_M_MODE + /* + * The hartid in a0 is expected later on, and we have no firmware + * to hand it to us. + */ + csrr a0, CSR_MHARTID +#endif + /* Load the global pointer */ .option push .option norelax