From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [RFC PATCH 00/14] Support timezone of ACPI TAD and EFI TIME Date: Fri, 20 Dec 2013 22:45:11 +0100 Message-ID: <2787644.ytU7M33B4r@vostro.rjw.lan> References: <1387439053-8711-1-git-send-email-jlee@suse.com> <1387517916.3539.4446.camel@linux-s257.site> <52B4B242.5010002@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <52B4B242.5010002-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "H. Peter Anvin" Cc: joeyli , Alessandro Zummo , Matt Fleming , Matthew Garrett , Elliott-VXdhtT5mjnY@public.gmane.org, samer.el-haj-mahmoud-VXdhtT5mjnY@public.gmane.org, Oliver Neukum , werner-IBi9RG/b67k@public.gmane.org, trenn-l3A5Bk7waGM@public.gmane.org, JBeulich-IBi9RG/b67k@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, "linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Borislav Petkov List-Id: linux-efi@vger.kernel.org On Friday, December 20, 2013 01:10:26 PM H. Peter Anvin wrote: > On 12/19/2013 09:38 PM, joeyli wrote: > > > > If don't use EFI time, then the first priority is using ACPI TAD if it > > present. Due to ACPI TAD is a generic acpi device that's need OS parsing > > DSDT table before set system time. > > > > Either move DSDT parser from subsystem initial stage to start_kernel or > > move timekeeping initial to after DSDT be parsed. Which one you think is > > more possible and risk less? Then I will try that way. > > > > I discussed the DSDT/SSDT parsing issue with Rafael and he claims it > would require a lot of restructuring. Unfortunately ACPI is at this > point done rather late, as I understand. All of this is a big problem. My understanding, however, is that to use the TAD, we don't actually need to create a struct acpi_device for it. We just need a handle to the ACPICA object which can be found using acpi_get_devices() as soon as the namespace has been extracted from the DSDT and friends. That in turn happens in acpi_early_init(), which is called from start_kernel() right before efi_late_init(). Is that early enough? Rafael