From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mx.groups.io with SMTP id smtpd.web10.38206.1639560062437862385 for ; Wed, 15 Dec 2021 01:21:02 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=HnMQi91j; spf=pass (domain: redhat.com, ip: 170.10.129.124, mailfrom: kraxel@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639560061; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=4Wwd4n/CvyV3gB5aR/k1mjjE0EbYkxzjL0CCsc+CS70=; b=HnMQi91jjgqGFF78s3fXXlCaVAaTyHXPCKRzL4RPLZbxddOeOiiiddAYQK84+nQgRaf+Ge bESChOyj79axLg/9dpmeughtf3ncGaVwPP4CdkL1JQHVYOGdQTku9cRM5mvZ6ZpW8OYESV nuEmVDPbVfh3DthZ8E8ytCHHvE4kN+g= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-407-rBZdbsMSMk6FxeONP-1QxQ-1; Wed, 15 Dec 2021 04:20:58 -0500 X-MC-Unique: rBZdbsMSMk6FxeONP-1QxQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B7CAB101796A; Wed, 15 Dec 2021 09:20:47 +0000 (UTC) Received: from sirius.home.kraxel.org (unknown [10.39.192.14]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7F9ED10927A7; Wed, 15 Dec 2021 09:20:47 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id F16AE180039F; Wed, 15 Dec 2021 10:20:45 +0100 (CET) Date: Wed, 15 Dec 2021 10:20:45 +0100 From: "Gerd Hoffmann" To: Min Xu Cc: devel@edk2.groups.io, Jiewen Yao , Anthony Perard , Julien Grall , Eric Dong , Ray Ni Subject: Re: [PATCH V4 29/31] UefiCpuPkg: Setting initial-count register as the last step Message-ID: <20211215092045.3t47szonafgfk4b2@sirius.home.kraxel.org> References: <13c45431a42352de4088e8bd1edd527b6b0a4d30.1639399598.git.min.m.xu@intel.com> MIME-Version: 1.0 In-Reply-To: <13c45431a42352de4088e8bd1edd527b6b0a4d30.1639399598.git.min.m.xu@intel.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kraxel@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Dec 13, 2021 at 08:57:00PM +0800, Min Xu wrote: > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3711 > > Per SDM, changing the mode of APIC timer (from one-shot to periodic or > vice versa) by writing to the timer LVT entry does not start the timer. > To start the timer, it is necessary to write to the initial-count > register. > > If initial-count is wrote before mode change, it's possible that timer > expired before the mode change. Thus failing the periodic mode. > > Cc: Jiewen Yao > Cc: Gerd Hoffmann > Cc: Anthony Perard > Cc: Julien Grall > Cc: Eric Dong > Cc: Ray Ni > Signed-off-by: Min Xu Acked-by: Gerd Hoffmann