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Wysocki" Subject: Re: [PATCH RESEND v3 1/6] i3c: mipi-i3c-hci: Add MIPI0100 ACPI ID to the I3C Support List Message-ID: References: <20240807052359.290046-1-Shyam-sundar.S-k@amd.com> <20240807052359.290046-2-Shyam-sundar.S-k@amd.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240809_085755_402424_BA3A03C5 X-CRM114-Status: GOOD ( 29.87 ) X-Mailman-Approved-At: Sat, 17 Aug 2024 02:59:57 -0700 X-BeenThere: linux-i3c@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-i3c" Errors-To: linux-i3c-bounces+linux-i3c=archiver.kernel.org@lists.infradead.org On Fri, Aug 09, 2024 at 09:02:35PM +0530, Shyam Sundar S K wrote: > On 8/9/2024 19:48, Andy Shevchenko wrote: > > On Fri, Aug 09, 2024 at 04:54:18PM +0300, Jarkko Nikula wrote: > >> On 8/7/24 8:23 AM, Shyam Sundar S K wrote: ... > > When adding a new ACPI ID, always provide the following information: > > > > 1) link (in some form) to the official confirmation / documentation for > > the allocated ID by the vendor (MIPI in this case) _OR_ (very exceptional!) > > why the bad ID had been allocated; > > Member version: > https://members.mipi.org/wg/All-Members/document/previewpdf/89465 > > Public version: https://www.mipi.org/mipi-disco-for-i3c-download (this > requires a signup). > > Since there is no direct link available for preview, I did not include > them in the commit-msg. But left a note that the MIPI ID is the one as > specified in the MIPI DisCo spec. It's fine. > > 2) are there devices in the wild (on the market) that use the being added ID(s)? > > Not in the wild. But the latest platform will have this support > included. So, these device IDs are crucial for the i3c-hci to be > supported on AMD platforms. Good, let's do it right then! > > 3) excerpt from the device (independently if it's public already, see above, > > or not) DSDT ACPI table. > > > > With the given patch it looks to me that you most likely need a local, AMD > > specific ID as well. > > > > So, in my ideal world the DSDT should be like > > > > Device (I3CC) > > { > > Name (_HID, "...") // AMD specific _HID > > Name (_CID, "MIPI0100") // Compatible ID for generic I3C controller > > ... > > } > > > > Is this the case? Why not? > > Please refer to the MIPI HCI I3C DisCo specification > (https://members.mipi.org/wg/All-Members/document/previewpdf/89465) > section 5.4. The ASL looks the same in case of AMD. > > MSFT says that they want to use MIPI0100 as mentioned in the > specification. MIPI doesn't know how to assign the ACPI ID correctly. But again, what I put in the above is the correct way of approaching. > What would you advise? Since my intuition and experience tells me that the two devices even based on the same IP are not the same (see word 'quirk' or '.driver_data' or alike in the kernel sources) the generic ID may not be used for the specific vendor unless it's _the only_ vendor for the certain IP. So, please do as I suggested above. And file a error report (and correction proposal) to the MIPI, so in "5.1 I3C Host Controller ACPI Hardware ID (_HID)" they should use _CID instead of _HID and add some text like "Each vendor should dedicate it's own _HID for the platform in question. The same _HID as _CID may be used if and only if vendor guarantees that there 100% compatibility with MIPI as described in this and other related documents." I.o.w. do you 100% guarantee that MIPI HCI I3C DisCo covers all necessary properties that you need for _your_ hardware? If not, use my approach, if yes, use the same _HID *and* _CID. Microsoft should know this as well and much better than MIPI. -- With Best Regards, Andy Shevchenko -- linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c