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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 05293C8300A for ; Tue, 28 Apr 2020 21:14:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC1F22072A for ; Tue, 28 Apr 2020 21:14:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="lotuZb7i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726946AbgD1VOu (ORCPT ); Tue, 28 Apr 2020 17:14:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726838AbgD1VOa (ORCPT ); Tue, 28 Apr 2020 17:14:30 -0400 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9058EC03C1AD for ; Tue, 28 Apr 2020 14:14:30 -0700 (PDT) Received: by mail-pj1-x1044.google.com with SMTP id a5so58166pjh.2 for ; Tue, 28 Apr 2020 14:14:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=zVfUJjoQXYq7Q5oA6c1LGX08NS1gs/+AFWoUELHCLf4=; b=lotuZb7ikMKen+euUq4MYRHGLpRk1lpOOhYyr+lbACpCGkuJmWMnOVrO5Bz/4UhgZA Ee+CNVT2V2NQd9mqCzWMHgT+2l7xhCxBegj/NSBq0XYvAV62beyTfh7CBzdKPDQU0lHr SOK4v6qIhEPhMhjep2PqK+3F8PIXAePU4Etdo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=zVfUJjoQXYq7Q5oA6c1LGX08NS1gs/+AFWoUELHCLf4=; b=rk9Wsid1Zkh9LgCm7M4aIzaT0aFJrNi/MDZwcgELlzvYsoe9LBfphuCXglxwzpFSQE PYFz3eyD6MPS2qnRlgXv2+duGGSCqlDbU8ZRhn/csTBLMKQdgEsGaHC+iMYAajXmnu95 FUfFeoObCV/JbFp8lkBZBQAV3hy3uRZVLKzjq2Ga+hwyibnTzofYwDqHGZZQ8DwsRo8t ohk35teMoUeg17CdEd3c6FRIy6y1YweCcxvhtW16X89eVJaSLUA8rY2syBCJPxR6rT/l bU4RyV7IaBMgHV4za+QCZwYqVTLeMGuk+lqGNj+f+tvYEBqnQiFO4mM8En4rDfGpxUX0 uIkw== X-Gm-Message-State: AGi0PuYwxzrsSqrjh4uJQi6GaYPzj1p0ZUwgILCdGq+bayWE7ZOXeAky QVEcHBBs//Ru93CXyYsW8g8axg== X-Google-Smtp-Source: APiQypJyRnxQ+Tm8c/YlbRxLWg1QPP9CCf113/B6ydU2dRpL9SRybJbsBBiVGqMWsZw/Zznm8eSiQw== X-Received: by 2002:a17:90a:1b4c:: with SMTP id q70mr7805600pjq.55.1588108470030; Tue, 28 Apr 2020 14:14:30 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id 18sm2988202pjf.30.2020.04.28.14.14.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2020 14:14:29 -0700 (PDT) From: Douglas Anderson To: jason.wessel@windriver.com, daniel.thompson@linaro.org, gregkh@linuxfoundation.org Cc: agross@kernel.org, kgdb-bugreport@lists.sourceforge.net, catalin.marinas@arm.com, linux-serial@vger.kernel.org, sumit.garg@linaro.org, corbet@lwn.net, mingo@redhat.com, will@kernel.org, hpa@zytor.com, tglx@linutronix.de, frowand.list@gmail.com, bp@alien8.de, bjorn.andersson@linaro.org, jslaby@suse.com, Douglas Anderson , Andrew Morton , Juergen Gross , Mauro Carvalho Chehab , Pawan Gupta , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 08/11] Documentation: kgdboc: Document new kgdboc_earlycon parameter Date: Tue, 28 Apr 2020 14:13:48 -0700 Message-Id: <20200428141218.v3.8.I7d5eb42c6180c831d47aef1af44d0b8be3fac559@changeid> X-Mailer: git-send-email 2.26.2.303.gf8c07b1a785-goog In-Reply-To: <20200428211351.85055-1-dianders@chromium.org> References: <20200428211351.85055-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org The recent patch ("kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles") adds a new kernel command line parameter. Document it. Note that the patch adding the feature does some comparing/contrasting of "kgdboc_earlycon" vs. the existing "ekgdboc". See that patch for more details, but briefly "ekgdboc" can be used _instead_ of "kgdboc" and just makes "kgdboc" do its normal initialization early (only works if your tty driver is already ready). The new "kgdboc_earlycon" works in combination with "kgdboc" and is backed by boot consoles. Signed-off-by: Douglas Anderson Reviewed-by: Greg Kroah-Hartman --- Changes in v3: - Added example in kgdb.rst - Removed unneeded sentence in kerenel-parameters doc. - Renamed earlycon_kgdboc to kgdboc_earlycon. - Suggest people use kgdboc_earlycon instead of ekgdboc. Changes in v2: None .../admin-guide/kernel-parameters.txt | 20 ++++++++++++++++ Documentation/dev-tools/kgdb.rst | 24 +++++++++++++++++++ 2 files changed, 44 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7bc83f3d9bdf..3b5ae06a98aa 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1190,6 +1190,11 @@ This is designed to be used in conjunction with the boot argument: earlyprintk=vga + This parameter works in place of the kgdboc parameter + but can only be used if the backing tty is available + very early in the boot process. For early debugging + via a serial port see kgdboc_earlycon instead. + edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} @@ -2105,6 +2110,21 @@ kms, kbd format: kms,kbd kms, kbd and serial format: kms,kbd,[,baud] + kgdboc_earlycon= [KGDB,HW] + If the boot console provides the ability to read + characters and can work in polling mode, you can use + this parameter to tell kgdb to use it as a backend + until the normal console is registered. Intended to + be used together with the kgdboc parameter which + specifies the normal console to transition to. + + The the name of the early console should be specified + as the value of this parameter. Note that the name of + the early console might be different than the tty + name passed to kgdboc. It's OK to leave the value + blank and the first boot console that implements + read() will be picked. + kgdbwait [KGDB] Stop kernel execution and enter the kernel debugger at the earliest opportunity. diff --git a/Documentation/dev-tools/kgdb.rst b/Documentation/dev-tools/kgdb.rst index d38be58f872a..61293f40bc6e 100644 --- a/Documentation/dev-tools/kgdb.rst +++ b/Documentation/dev-tools/kgdb.rst @@ -274,6 +274,30 @@ don't like this are to hack gdb to send the :kbd:`SysRq-G` for you as well as on the initial connect, or to use a debugger proxy that allows an unmodified gdb to do the debugging. +Kernel parameter: ``kgdboc_earlycon`` +------------------------------------- + +If you specify the kernel parameter ``kgdboc_earlycon`` and your serial +driver registers a boot console that supports polling (doesn't need +interrupts and implements a nonblocking read() function) kgdb will attempt +to work using the boot console until it can transition to the regular +tty driver specified by the ``kgdboc`` parameter. + +Normally there is only one boot console (especially that implements the +read() function) so just adding ``kgdboc_earlycon`` on its own is +sufficient to make this work. If you have more than one boot console you +can add the boot console's name to differentiate. Note that names that +are registered through the boot console layer and the tty layer are not +the same for the same port. + +For instance, on one board to be explicit you might do:: + + kgdboc_earlycon=qcom_geni kgdboc=ttyMSM0 + +If the only boot console on the device was "qcom_geni", you could simplify:: + + kgdboc_earlycon kgdboc=ttyMSM0 + Kernel parameter: ``kgdbwait`` ------------------------------ -- 2.26.2.303.gf8c07b1a785-goog