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Thu, 8 Apr 2021 19:46:56 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.5.0-alpha0-273-g8500d2492d-fm-20210323.002-g8500d249 Mime-Version: 1.0 Message-Id: <6ff29d26-543a-4790-abb4-ebaa3f8d0265@www.fastmail.com> In-Reply-To: <20210408121441.GG7166@minyard.net> References: <20210319061952.145040-1-andrew@aj.id.au> <2db77e16-3f44-4c02-a7ba-a4fac8141ae3@www.fastmail.com> <20210408121441.GG7166@minyard.net> Date: Fri, 09 Apr 2021 09:16:35 +0930 From: "Andrew Jeffery" To: "Corey Minyard" Cc: openipmi-developer@lists.sourceforge.net, openbmc@lists.ozlabs.org, "Joel Stanley" , "Ryan Chen" , devicetree@vger.kernel.org, "Tomer Maimon" , linux-aspeed@lists.ozlabs.org, linux-gpio@vger.kernel.org, "Avi Fishman" , "Patrick Venture" , "Linus Walleij" , linux-kernel@vger.kernel.org, "Tali Perry" , "Rob Herring" , "Lee Jones" , "Chia-Wei, Wang" , linux-arm-kernel@lists.infradead.org, "Benjamin Fair" Subject: Re: [PATCH v2 00/21] ipmi: Allow raw access to KCS devices Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, 8 Apr 2021, at 21:44, Corey Minyard wrote: > On Thu, Apr 08, 2021 at 10:27:46AM +0930, Andrew Jeffery wrote: > > Hi Corey, > > > > On Fri, 19 Mar 2021, at 16:49, Andrew Jeffery wrote: > > > Hello, > > > > > > This series is a bit of a mix of things, but its primary purpose is to > > > expose BMC KCS IPMI devices to userspace in a way that enables userspace > > > to talk to host firmware using protocols that are not IPMI. > > > > > > v1 can be found here: > > > > > > https://lore.kernel.org/openbmc/20210219142523.3464540-1-andrew@aj.id.au/ > > > > > > Changes in v2 include: > > > > > > * A rebase onto v5.12-rc2 > > > * Incorporation of off-list feedback on SerIRQ configuration from > > > Chiawei > > > * Further validation on hardware for ASPEED KCS devices 2, 3 and 4 > > > * Lifting the existing single-open constraint of the IPMI chardev > > > * Fixes addressing Rob's feedback on the conversion of the ASPEED KCS > > > binding to dt-schema > > > * Fixes addressing Rob's feedback on the new aspeed,lpc-interrupts > > > property definition for the ASPEED KCS binding > > > > > > A new chardev device is added whose implementation exposes the Input > > > Data Register (IDR), Output Data Register (ODR) and Status Register > > > (STR) via read() and write(), and implements poll() for event > > > monitoring. > > > > > > The existing /dev/ipmi-kcs* chardev interface exposes the KCS devices in > > > a way which encoded the IPMI protocol in its behaviour. However, as > > > LPC[0] KCS devices give us bi-directional interrupts between the host > > > and a BMC with both a data and status byte, they are useful for purposes > > > beyond IPMI. > > > > > > As a concrete example, libmctp[1] implements a vendor-defined MCTP[2] > > > binding using a combination of LPC Firmware cycles for bulk data > > > transfer and a KCS device via LPC IO cycles for out-of-band protocol > > > control messages[3]. This gives a throughput improvement over the > > > standard KCS binding[4] while continuing to exploit the ease of setup of > > > the LPC bus for early boot firmware on the host processor. > > > > > > The series takes a bit of a winding path to achieve its aim: > > > > > > 1. It begins with patches 1-5 put together by Chia-Wei, which I've > > > rebased on v5.12-rc2. These fix the ASPEED LPC bindings and other > > > non-KCS LPC-related ASPEED device drivers in a way that enables the > > > SerIRQ patches at the end of the series. With Joel's review I'm hoping > > > these 5 can go through the aspeed tree, and that the rest can go through > > > the IPMI tree. > > > > > > 2. Next, patches 6-13 fairly heavily refactor the KCS support in the > > > IPMI part of the tree, re-architecting things such that it's possible to > > > support multiple chardev implementations sitting on top of the ASPEED > > > and Nuvoton device drivers. However, the KCS code didn't really have > > > great separation of concerns as it stood, so even if we disregard the > > > multiple-chardev support I think the cleanups are worthwhile. > > > > > > 3. Patch 14 adds some interrupt management capabilities to the KCS > > > device drivers in preparation for patch 16, which introduces the new > > > "raw" KCS device interface. I'm not stoked about the device name/path, > > > so if people are looking to bikeshed something then feel free to lay > > > into that. > > > > > > 4. The remaining patches switch the ASPEED KCS devicetree binding to > > > dt-schema, add a new interrupt property to describe the SerIRQ behaviour > > > of the device and finally clean up Serial IRQ support in the ASPEED KCS > > > driver. > > > > > > Rob: The dt-binding patches still come before the relevant driver > > > changes, I tried to keep the two close together in the series, hence the > > > bindings changes not being patches 1 and 2. > > > > > > I've exercised the series under qemu with the rainier-bmc machine plus > > > additional patches for KCS support[5]. I've also substituted this series in > > > place of a hacky out-of-tree driver that we've been using for the > > > libmctp stack and successfully booted the host processor under our > > > internal full-platform simulation tools for a Rainier system. > > > > > > Note that this work touches the Nuvoton driver as well as ASPEED's, but > > > I don't have the capability to test those changes or the IPMI chardev > > > path. Tested-by tags would be much appreciated if you can exercise one > > > or both. > > > > > > Please review! > > > > Unfortunately the cover letter got detached from the rest of the series. > > > > Any chance you can take a look at the patches? > > There were some minor concerns that were unanswered, and there really > was no review by others for many of the patches. Right; I was planning to clean up the minor concerns once I'd received some more feedback. I could have done a better job of communicating that :) > > I would like this patch set, it makes some good cleanups. But I would > like some more review and testing by others, if possible. No worries. I'm trying to rope some others in to take a look. Thanks for the response. Andrew