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Mon, 31 Aug 2020 21:40:52 +0000 Received: from DM6PR11MB3963.namprd11.prod.outlook.com ([fe80::5ca6:6956:d7f6:2c55]) by DM6PR11MB3963.namprd11.prod.outlook.com ([fe80::5ca6:6956:d7f6:2c55%7]) with mapi id 15.20.3283.028; Mon, 31 Aug 2020 21:40:52 +0000 From: "Mani, Rajmohan" To: Greg Kroah-Hartman CC: Heikki Krogerus , Darren Hart , Andy Shevchenko , Mika Westerberg , Dmitry Torokhov , Lee Jones , Ayman Bagabas , Masahiro Yamada , "Joseph, Jithu" , =?iso-8859-2?Q?Bla=BE_Hrastnik?= , Srinivas Pandruvada , "linux-kernel@vger.kernel.org" , "platform-driver-x86@vger.kernel.org" , "linux-usb@vger.kernel.org" , "pmalani@chromium.org" , "bleung@chromium.org" Subject: RE: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager (IOM) driver Thread-Topic: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager (IOM) driver Thread-Index: AQHWeD6ZmieVJ7ILtEmVT73DLNf2fqlNLX2AgAAXoACAAGapYIAA/qCAgAQfx0A= Date: Mon, 31 Aug 2020 21:40:52 +0000 Message-ID: References: <20200822040508.23510-1-rajmohan.mani@intel.com> <20200822040508.23510-2-rajmohan.mani@intel.com> <20200828074359.GC942935@kroah.com> <20200828090832.GB174928@kuha.fi.intel.com> <20200829062719.GA80106@kroah.com> In-Reply-To: <20200829062719.GA80106@kroah.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.5.1.3 authentication-results: linuxfoundation.org; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR11MB3963.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6079498f-1fc2-4249-c1b3-08d84df688a9 X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Aug 2020 21:40:52.1915 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: a5y0LTxOm8lg/JmkP5RshoMBG/gTjaXvVEkU/A7mjDu2W3SQSY9VK4PQHMQXYsFd1lOmWH0sw8zzOsVd0AVy9Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR11MB1499 X-OriginatorOrg: intel.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager > (IOM) driver >=20 > On Fri, Aug 28, 2020 at 03:20:22PM +0000, Mani, Rajmohan wrote: > > Hi Greg, > > > > > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output > > > Manager > > > (IOM) driver > > > > > > Hi Greg, > > > > > > On Fri, Aug 28, 2020 at 09:43:59AM +0200, Greg Kroah-Hartman wrote: > > > > I still find this crazy that a whole separate driver is created > > > > just to read a single 32bit value. > > > > > > > > Why not put this logic in the driver that wants to read that value? > > > > That would be much simpler, smaller, and more obvious. > > > > > > That would mean that we start maintaining something like DMI quirk > > > table in those drivers. Unfortunately the IOM device is not available= on > every platform. > > > Also, even on platforms that do have it, there is no guarantee that > > > the device is always going to be mapped to the same address. > > > > > > Nevertheless, I was originally hoping that we could hide the > > > handling of IOM somehow in ACPI without the need for an actual > > > device object, but it now turns out that the other features of the > > > IOM chip have created interest. At least our i915 guys probable have > > > some use for it (I don't know exactly what they are planning to use i= t for). > > > > > > So the fact that we may later need the device for something else, on > > > top of the clumsiness and most importantly risks involved with using > > > ACPI to take care of extra tasks (ASL tends to have bugs - bugs that > > > may never ever get fixed), I think the IOM device object, and the > > > driver that binds to it, do have a valid reason for existing. > > > > > > > Intel PMC USB mux device is part of the PCH, while IOM is part of the S= oC. >=20 > I have no idea what a "PCH" is, what "IOM" is, and how any of this relate= s to a > "SoC" :) >=20 I was just meaning to say IOM (Intel Output Manager) is a separate device, = that is not part of PCH (Platform Controller Hub) like PMC (Power Management Con= troller). For the sake of completeness PCH - Platform Controller Hub (usually that handles I/Os in Intel core plat= forms) IOM - Input Output Manager (IOM) is part of the Tiger Lake SoC that handles= Type-C topology, configuration and PM functions of various Type-C devices connecte= d on the platform > Don't impose arbritrary hardware "splits" to kernel code when the kernel = has > no such "partitioning" please. >=20 Ack. > > This was another reason we had to have a separate ACPI device. >=20 > That sounds like a firmware issue you can solve in UEFI. >=20 Ack > I think this is the most TLA-laden email I have ever written, and I used = to work > at IBM :) I thought it was only Intel where TLAs are abundantly used. Thanks for the reviews and the direction on this topic. >=20 > greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mani, Rajmohan" Subject: RE: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager (IOM) driver Date: Mon, 31 Aug 2020 21:40:52 +0000 Message-ID: References: <20200822040508.23510-1-rajmohan.mani@intel.com> <20200822040508.23510-2-rajmohan.mani@intel.com> <20200828074359.GC942935@kroah.com> <20200828090832.GB174928@kuha.fi.intel.com> <20200829062719.GA80106@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20200829062719.GA80106@kroah.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman Cc: Heikki Krogerus , Darren Hart , Andy Shevchenko , Mika Westerberg , Dmitry Torokhov , Lee Jones , Ayman Bagabas , Masahiro Yamada , "Joseph, Jithu" , =?iso-8859-2?Q?Bla=BE_Hrastnik?= , Srinivas Pandruvada , "linux-kernel@vger.kernel.org" , "platform-driver-x86@vger.kernel.org" , "linux-usb@vger.kernel.org" , "pmalani@chromium.org" , "bleung@chromium.org" List-Id: platform-driver-x86.vger.kernel.org Hi Greg, > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager > (IOM) driver >=20 > On Fri, Aug 28, 2020 at 03:20:22PM +0000, Mani, Rajmohan wrote: > > Hi Greg, > > > > > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output > > > Manager > > > (IOM) driver > > > > > > Hi Greg, > > > > > > On Fri, Aug 28, 2020 at 09:43:59AM +0200, Greg Kroah-Hartman wrote: > > > > I still find this crazy that a whole separate driver is created > > > > just to read a single 32bit value. > > > > > > > > Why not put this logic in the driver that wants to read that value? > > > > That would be much simpler, smaller, and more obvious. > > > > > > That would mean that we start maintaining something like DMI quirk > > > table in those drivers. Unfortunately the IOM device is not available= on > every platform. > > > Also, even on platforms that do have it, there is no guarantee that > > > the device is always going to be mapped to the same address. > > > > > > Nevertheless, I was originally hoping that we could hide the > > > handling of IOM somehow in ACPI without the need for an actual > > > device object, but it now turns out that the other features of the > > > IOM chip have created interest. At least our i915 guys probable have > > > some use for it (I don't know exactly what they are planning to use i= t for). > > > > > > So the fact that we may later need the device for something else, on > > > top of the clumsiness and most importantly risks involved with using > > > ACPI to take care of extra tasks (ASL tends to have bugs - bugs that > > > may never ever get fixed), I think the IOM device object, and the > > > driver that binds to it, do have a valid reason for existing. > > > > > > > Intel PMC USB mux device is part of the PCH, while IOM is part of the S= oC. >=20 > I have no idea what a "PCH" is, what "IOM" is, and how any of this relate= s to a > "SoC" :) >=20 I was just meaning to say IOM (Intel Output Manager) is a separate device, = that is not part of PCH (Platform Controller Hub) like PMC (Power Management Con= troller). For the sake of completeness PCH - Platform Controller Hub (usually that handles I/Os in Intel core plat= forms) IOM - Input Output Manager (IOM) is part of the Tiger Lake SoC that handles= Type-C topology, configuration and PM functions of various Type-C devices connecte= d on the platform > Don't impose arbritrary hardware "splits" to kernel code when the kernel = has > no such "partitioning" please. >=20 Ack. > > This was another reason we had to have a separate ACPI device. >=20 > That sounds like a firmware issue you can solve in UEFI. >=20 Ack > I think this is the most TLA-laden email I have ever written, and I used = to work > at IBM :) I thought it was only Intel where TLAs are abundantly used. Thanks for the reviews and the direction on this topic. >=20 > greg k-h