From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 456C1C7618A for ; Mon, 20 Mar 2023 14:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229665AbjCTORk (ORCPT ); Mon, 20 Mar 2023 10:17:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231663AbjCTORg (ORCPT ); Mon, 20 Mar 2023 10:17:36 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9315927D67; Mon, 20 Mar 2023 07:17:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 774DFCE12B0; Mon, 20 Mar 2023 14:17:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49F98C433A8; Mon, 20 Mar 2023 14:17:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679321849; bh=aKMxejypqYGtstTSZaALmz6QKeR6kRQMkXNt7PN5Rqo=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=HeeQW3bmMhNgQRTD1yzFc05O7cqd4QMqRZbOzM6RVy0l/OU6l/B2M098aPIYWHFnZ w1syANmqkE/2tE2lE3GWwohKchzVNNmDRN6FHgGitTW7i8i18rT96Ttr6/03jU9qtj /EJ5tt773bkfCEYA3i0Gx4DH7J88hIVkWG4C5RNOo1XExBGt2goYmuZitboZnMxBUb FFwx9fmYla8b2S6wwMIlYqg543d/D6dC5dSh8PhbP7/IczhB3OUxgL+tZ9U1VNG0GH hYtpngaP+u8NYfB2T8V2Q3yWI5wSOI950eHFR/8lVz3CZUypC1kCafMfeS81l2tUtw Xig94ETO/6ZPg== Received: by mail-ua1-f50.google.com with SMTP id ay14so7979144uab.13; Mon, 20 Mar 2023 07:17:29 -0700 (PDT) X-Gm-Message-State: AO0yUKUR/5UXYlUpWtSAvqm36VcEyBk/6BmDI0v2OSWTe0UWGlYKgWZ7 Gid3ddDYhmr+u9UTON2s/m2B70h6uHf/R75Yfg== X-Google-Smtp-Source: AK7set/6eiFW2xFlHjvRE53ibb1vDYufRHrv7hCBpS4QB9kFF8AO/fAfVdO8LHihe5D01sI28nuWjz4W3poi8n3cClc= X-Received: by 2002:a1f:9ed3:0:b0:418:4529:a308 with SMTP id h202-20020a1f9ed3000000b004184529a308mr3939800vke.3.1679321848147; Mon, 20 Mar 2023 07:17:28 -0700 (PDT) MIME-Version: 1.0 References: <20230317030501.1811905-1-anshuman.khandual@arm.com> In-Reply-To: <20230317030501.1811905-1-anshuman.khandual@arm.com> From: Rob Herring Date: Mon, 20 Mar 2023 09:17:16 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 0/7] coresight: etm4x: Migrate AMBA devices to platform driver To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, suzuki.poulose@arm.com, scclevenger@os.amperecomputing.com, Frank Rowand , Russell King , Greg Kroah-Hartman , "Rafael J. Wysocki" , Len Brown , Sudeep Holla , Lorenzo Pieralisi , Mathieu Poirier , Mike Leach , Leo Yan , devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Thu, Mar 16, 2023 at 10:05=E2=80=AFPM Anshuman Khandual wrote: > > CoreSight ETM4x devices could be accessed either via MMIO (handled via > amba_driver) or CPU system instructions (handled via platform driver). Bu= t > this has the following issues : > > - Each new CPU comes up with its own PID and thus we need to keep on > adding the "known" PIDs to get it working with AMBA driver. While > the ETM4 architecture (and CoreSight architecture) defines way to > identify a device as ETM4. Thus older kernels won't be able to > "discover" a newer CPU, unless we add the PIDs. But v8.4 discourages MMIO access, so this problem will go away on its own. Even if not, adding IDs to stable kernels is standard practice whether it is PCI VID/PID, compatible string or AMBA PID. > - With ACPI, the ETM4x devices have the same HID to identify the device > irrespective of the mode of access. This creates a problem where two > different drivers (both AMBA based driver and platform driver) would > hook into the "HID" and could conflict. e.g., if AMBA driver gets > hold of a non-MMIO device, the probe fails. If we have single driver > hooked into the given "HID", we could handle them seamlessly, > irrespective of the mode of access. Why are we changing DT for ACPI? Just always use the platform driver for ACPI and leave DT systems alone. > - CoreSight is heavily dependent on the runtime power management. With > ACPI, amba_driver doesn't get us anywhere with handling the power > and thus one need to always turn the power ON to use them. Moving to > platform driver gives us the power management for free. This sounds like an issue for any amba driver. If this is an issue, solve it for everyone, not just work around it in one driver. When someone puts another primecell device into an ACPI system, are we going to go do the same one-off change in that driver too? (We kind of already did with SBSA UART...) Rob From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DA7D6C7618A for ; Mon, 20 Mar 2023 14:18:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=fGTeT6ZeGutSeQzu30GPc9mCNr7okdEpqrxkpzXJ20k=; b=r1o1utCSe5GvAi bnPNujYm1Skl5bnJP0bmGdyAbYLozyoA04LacPYGZcPOuLKSCGSzbv+i+mTVGyWLYLjU6/jyJ00wH kLEk3QAYbVyw9PRK6AeS08SW9ifDpY6wVH9M3BQkBl0aGEr1+HsgYiYVu80xwM+Av5c5JTVnURq7g mSoRbLu85Biixy1nvEbxklwwoiU56DOqytB5OfNn/XVS5M5SlX512WtmD8pJC+pw1Se0oL9rX2bik 0guqLb22UKy7x3wV70OscZVs5jw4YrWbOQS1cYB6/4nCPrrkRG2fAKzxGw9yLwQASlhaMJxhYiplQ E2PNA3b18Pev+jtFWnug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1peGKR-009Ite-2m; Mon, 20 Mar 2023 14:17:39 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1peGKO-009Ise-37 for linux-arm-kernel@lists.infradead.org; Mon, 20 Mar 2023 14:17:38 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 244EDCE128B for ; Mon, 20 Mar 2023 14:17:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40EC5C4339C for ; Mon, 20 Mar 2023 14:17:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679321849; bh=aKMxejypqYGtstTSZaALmz6QKeR6kRQMkXNt7PN5Rqo=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=HeeQW3bmMhNgQRTD1yzFc05O7cqd4QMqRZbOzM6RVy0l/OU6l/B2M098aPIYWHFnZ w1syANmqkE/2tE2lE3GWwohKchzVNNmDRN6FHgGitTW7i8i18rT96Ttr6/03jU9qtj /EJ5tt773bkfCEYA3i0Gx4DH7J88hIVkWG4C5RNOo1XExBGt2goYmuZitboZnMxBUb FFwx9fmYla8b2S6wwMIlYqg543d/D6dC5dSh8PhbP7/IczhB3OUxgL+tZ9U1VNG0GH hYtpngaP+u8NYfB2T8V2Q3yWI5wSOI950eHFR/8lVz3CZUypC1kCafMfeS81l2tUtw Xig94ETO/6ZPg== Received: by mail-ua1-f46.google.com with SMTP id n17so7985617uaj.10 for ; Mon, 20 Mar 2023 07:17:29 -0700 (PDT) X-Gm-Message-State: AO0yUKUMj40IH456DLF4WDUgXXba2utT6si00B3hHvAf77DHrW41jh37 3x3PfdNAxbdNQhD1ZIaWtmdHj+EbnENr+VQn8Q== X-Google-Smtp-Source: AK7set/6eiFW2xFlHjvRE53ibb1vDYufRHrv7hCBpS4QB9kFF8AO/fAfVdO8LHihe5D01sI28nuWjz4W3poi8n3cClc= X-Received: by 2002:a1f:9ed3:0:b0:418:4529:a308 with SMTP id h202-20020a1f9ed3000000b004184529a308mr3939800vke.3.1679321848147; Mon, 20 Mar 2023 07:17:28 -0700 (PDT) MIME-Version: 1.0 References: <20230317030501.1811905-1-anshuman.khandual@arm.com> In-Reply-To: <20230317030501.1811905-1-anshuman.khandual@arm.com> From: Rob Herring Date: Mon, 20 Mar 2023 09:17:16 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 0/7] coresight: etm4x: Migrate AMBA devices to platform driver To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, suzuki.poulose@arm.com, scclevenger@os.amperecomputing.com, Frank Rowand , Russell King , Greg Kroah-Hartman , "Rafael J. Wysocki" , Len Brown , Sudeep Holla , Lorenzo Pieralisi , Mathieu Poirier , Mike Leach , Leo Yan , devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230320_071737_473081_DA92C3CC X-CRM114-Status: GOOD ( 24.61 ) X-BeenThere: linux-arm-kernel@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="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCBNYXIgMTYsIDIwMjMgYXQgMTA6MDXigK9QTSBBbnNodW1hbiBLaGFuZHVhbAo8YW5z aHVtYW4ua2hhbmR1YWxAYXJtLmNvbT4gd3JvdGU6Cj4KPiBDb3JlU2lnaHQgRVRNNHggZGV2aWNl cyBjb3VsZCBiZSBhY2Nlc3NlZCBlaXRoZXIgdmlhIE1NSU8gKGhhbmRsZWQgdmlhCj4gYW1iYV9k cml2ZXIpIG9yIENQVSBzeXN0ZW0gaW5zdHJ1Y3Rpb25zIChoYW5kbGVkIHZpYSBwbGF0Zm9ybSBk cml2ZXIpLiBCdXQKPiB0aGlzIGhhcyB0aGUgZm9sbG93aW5nIGlzc3VlcyA6Cj4KPiAgIC0gRWFj aCBuZXcgQ1BVIGNvbWVzIHVwIHdpdGggaXRzIG93biBQSUQgYW5kIHRodXMgd2UgbmVlZCB0byBr ZWVwIG9uCj4gICAgIGFkZGluZyB0aGUgImtub3duIiBQSURzIHRvIGdldCBpdCB3b3JraW5nIHdp dGggQU1CQSBkcml2ZXIuIFdoaWxlCj4gICAgIHRoZSBFVE00IGFyY2hpdGVjdHVyZSAoYW5kIENv cmVTaWdodCBhcmNoaXRlY3R1cmUpIGRlZmluZXMgd2F5IHRvCj4gICAgIGlkZW50aWZ5IGEgZGV2 aWNlIGFzIEVUTTQuIFRodXMgb2xkZXIga2VybmVscyAgd29uJ3QgYmUgYWJsZSB0bwo+ICAgICAi ZGlzY292ZXIiIGEgbmV3ZXIgQ1BVLCB1bmxlc3Mgd2UgYWRkIHRoZSBQSURzLgoKQnV0IHY4LjQg ZGlzY291cmFnZXMgTU1JTyBhY2Nlc3MsIHNvIHRoaXMgcHJvYmxlbSB3aWxsIGdvIGF3YXkgb24g aXRzCm93bi4gRXZlbiBpZiBub3QsIGFkZGluZyBJRHMgdG8gc3RhYmxlIGtlcm5lbHMgaXMgc3Rh bmRhcmQgcHJhY3RpY2UKd2hldGhlciBpdCBpcyBQQ0kgVklEL1BJRCwgY29tcGF0aWJsZSBzdHJp bmcgb3IgQU1CQSBQSUQuCgo+ICAgLSBXaXRoIEFDUEksIHRoZSBFVE00eCBkZXZpY2VzIGhhdmUg dGhlIHNhbWUgSElEIHRvIGlkZW50aWZ5IHRoZSBkZXZpY2UKPiAgICAgaXJyZXNwZWN0aXZlIG9m IHRoZSBtb2RlIG9mIGFjY2Vzcy4gVGhpcyBjcmVhdGVzIGEgcHJvYmxlbSB3aGVyZSB0d28KPiAg ICAgZGlmZmVyZW50IGRyaXZlcnMgKGJvdGggQU1CQSBiYXNlZCBkcml2ZXIgYW5kIHBsYXRmb3Jt IGRyaXZlcikgd291bGQKPiAgICAgaG9vayBpbnRvIHRoZSAiSElEIiBhbmQgY291bGQgY29uZmxp Y3QuIGUuZy4sIGlmIEFNQkEgZHJpdmVyIGdldHMKPiAgICAgaG9sZCBvZiBhIG5vbi1NTUlPIGRl dmljZSwgdGhlIHByb2JlIGZhaWxzLiBJZiB3ZSBoYXZlIHNpbmdsZSBkcml2ZXIKPiAgICAgaG9v a2VkIGludG8gdGhlIGdpdmVuICJISUQiLCB3ZSBjb3VsZCBoYW5kbGUgdGhlbSBzZWFtbGVzc2x5 LAo+ICAgICBpcnJlc3BlY3RpdmUgb2YgdGhlIG1vZGUgb2YgYWNjZXNzLgoKV2h5IGFyZSB3ZSBj aGFuZ2luZyBEVCBmb3IgQUNQST8gSnVzdCBhbHdheXMgdXNlIHRoZSBwbGF0Zm9ybSBkcml2ZXIK Zm9yIEFDUEkgYW5kIGxlYXZlIERUIHN5c3RlbXMgYWxvbmUuCgo+ICAgLSBDb3JlU2lnaHQgaXMg aGVhdmlseSBkZXBlbmRlbnQgb24gdGhlIHJ1bnRpbWUgcG93ZXIgbWFuYWdlbWVudC4gV2l0aAo+ ICAgICBBQ1BJLCBhbWJhX2RyaXZlciBkb2Vzbid0IGdldCB1cyBhbnl3aGVyZSB3aXRoIGhhbmRs aW5nIHRoZSBwb3dlcgo+ICAgICBhbmQgdGh1cyBvbmUgbmVlZCB0byBhbHdheXMgdHVybiB0aGUg cG93ZXIgT04gdG8gdXNlIHRoZW0uIE1vdmluZyB0bwo+ICAgICBwbGF0Zm9ybSBkcml2ZXIgZ2l2 ZXMgdXMgdGhlIHBvd2VyIG1hbmFnZW1lbnQgZm9yIGZyZWUuCgpUaGlzIHNvdW5kcyBsaWtlIGFu IGlzc3VlIGZvciBhbnkgYW1iYSBkcml2ZXIuIElmIHRoaXMgaXMgYW4gaXNzdWUsCnNvbHZlIGl0 IGZvciBldmVyeW9uZSwgbm90IGp1c3Qgd29yayBhcm91bmQgaXQgaW4gb25lIGRyaXZlci4KCldo ZW4gc29tZW9uZSBwdXRzIGFub3RoZXIgcHJpbWVjZWxsIGRldmljZSBpbnRvIGFuIEFDUEkgc3lz dGVtLCBhcmUgd2UKZ29pbmcgdG8gZ28gZG8gdGhlIHNhbWUgb25lLW9mZiBjaGFuZ2UgaW4gdGhh dCBkcml2ZXIgdG9vPyAoV2Uga2luZCBvZgphbHJlYWR5IGRpZCB3aXRoIFNCU0EgVUFSVC4uLikK ClJvYgoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbGlu dXgtYXJtLWtlcm5lbCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtlcm5lbEBsaXN0cy5pbmZyYWRl YWQub3JnCmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgt YXJtLWtlcm5lbAo=