From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Masters Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver Date: Thu, 10 Sep 2015 18:45:17 -0400 Message-ID: <55F207FD.2030007@redhat.com> References: <=fu.wei@linaro.org> <1433217907-928-1-git-send-email-fu.wei@linaro.org> <1433217907-928-6-git-send-email-fu.wei@linaro.org> <556F4489.6030206@codeaurora.org> <20150603182503.GD6460@roeck-us.net> <556F4D29.1080001@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <556F4D29.1080001@codeaurora.org> Sender: linux-doc-owner@vger.kernel.org To: Timur Tabi , Guenter Roeck Cc: fu.wei@linaro.org, Suravee.Suthikulpanit@amd.com, linaro-acpi@lists.linaro.org, linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, tekkamanninja@gmail.com, graeme.gregory@linaro.org, al.stone@linaro.org, hanjun.guo@linaro.org, ashwin.chaugule@linaro.org, arnd@arndb.de, vgandhi@codeaurora.org, wim@iguana.be, leo.duran@amd.com, corbet@lwn.net, mark.rutland@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, rjw@rjwysocki.net List-Id: devicetree@vger.kernel.org On 06/03/2015 02:53 PM, Timur Tabi wrote: > On 06/03/2015 01:25 PM, Guenter Roeck wrote: >> In general the idea here would be to use a crashdump kernel, which, >> when loaded, would reset the watchdog before it fires. This kernel >> would then write a core dump to a specified location. > > What is the mechanism for resetting the watchdog? The only code that > knows about the hardware registers is this driver. Does the crashdump > kernel call the watchdog stop function? > >> If arm64 doesn't support a crashdump kernel, it might still be possible >> to log the backtrace somewhere (eg in nvram using pstore if that is >> supported via acpi or efi). Just to go back and explicitly answer this, arm64 does have support for crashdump, using the standard kexec/kdump approach, exactly as on x86. There's still some more work to be done to get the ACPI case fully upstream (e.g. on X-Gene platforms such as the HP ProLiant Moonshot m400 we need non-PSCI CPU parking protocol offlining when booting in UEFI/ACPI mode), but it's what we are doing in RHEL(SA) and the goal is to help clean up the remaining pieces upstream there. Jon.