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 22999C0015E for ; Wed, 26 Jul 2023 17:33:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232525AbjGZRdJ (ORCPT ); Wed, 26 Jul 2023 13:33:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232608AbjGZRdC (ORCPT ); Wed, 26 Jul 2023 13:33:02 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AE31E2689; Wed, 26 Jul 2023 10:33:00 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2123E2F4; Wed, 26 Jul 2023 10:33:43 -0700 (PDT) Received: from [10.57.82.133] (unknown [10.57.82.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 648593F67D; Wed, 26 Jul 2023 10:32:57 -0700 (PDT) Message-ID: <1b30a44e-519c-d4d5-ff98-f246cd70fe7c@arm.com> Date: Wed, 26 Jul 2023 18:32:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH V6 0/6] coresight: etm4x: Migrate ACPI AMBA devices to platform driver To: Steve Clevenger OS , Anshuman Khandual , "linux-arm-kernel@lists.infradead.org" , "coresight@lists.linaro.org" , "gregkh@linuxfoundation.org" , "rafael@kernel.org" Cc: Ganapatrao Kulkarni OS , Rob Herring , Frank Rowand , Russell King , 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" References: <20230710062500.45147-1-anshuman.khandual@arm.com> <9c3b4a97-bbe2-a978-b000-9562123af523@arm.com> From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/07/2023 18:03, Steve Clevenger OS wrote: > > Hi Suzuki, > > On 7/26/2023 9:59 AM, Suzuki K Poulose wrote: >> On 10/07/2023 07:24, Anshuman Khandual wrote: >>> CoreSight ETM4x devices could be accessed either via MMIO (handled via >>> amba_driver) or CPU system instructions (handled via platform driver). >>> But >>> 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. >>> >>>    - 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. >>> >>>    - 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. >>> >>> Due to all of the above, we are moving ACPI MMIO based etm4x devices >>> to be >>> supported via tha platform driver. The series makes the existing platform >>> driver generic to handle both type of the access modes. Although existing >>> AMBA driver would still continue to support DT based etm4x MMIO devices. >>> Although some problems still remain, such as manually adding PIDs for all >>> new AMBA DT based devices. >>> >>> The series applies on 6.5-rc1. >>> >>> Changes in V6: >>> >>> - Rebased on 6.5-rc1 >>> >> >> I have queued this version for v6.6, should appear on coresight/next soon. >> >> Suzuki > > Is there anyway to queue this for 6.5? Or has that ship sailed? Only fixes are allowed for v6.5 at this time. Suzuki > > Thanks, > > Steve C.