From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooks Subject: pinctrl-amd: What hardware does it apply to? Date: Thu, 21 Dec 2017 08:25:03 +1000 Message-ID: <6c675643-45ec-c57f-f1b2-afb25f3e947e@opengear.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bl2nam02on0084.outbound.protection.outlook.com ([104.47.38.84]:24448 "EHLO NAM02-BL2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754428AbdLTWZZ (ORCPT ); Wed, 20 Dec 2017 17:25:25 -0500 Content-Language: en-US Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org To: Linus Walleij , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Nehal Shah , Shyam Sundar S K , Ken Xue , Tobias Diedrich , Sudheesh Mavila , platypus-sw Hi Linus I'm working on gpio for an AMD Family 16h Model 30h system[1]. The SoC is the same as the GX412-TC used in the PC Engines APU2. There is an out-of-tree gpio driver (gpio-amd) for this SoC in the meta-amd yocto layer[2]. Another driver (gpio-sb8xx) was submitted for upstream inclusion, but was knocked back with the suggestion that pinctrl is the way forward[3]. I would much prefer to use a mainline driver for the system I'm working on, so I'm looking at the pinctrl-amd driver to see whether it applies to our SoC, or whether it could be extended, or used as starting point for a new driver. The out-of-tree drivers apply to the GX412-TC SoC and uses PCI for probing: gpio-amd registers a platform driver that applies to { PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_HUDSON2_SMBUS } gpio-sb8xx applies to { PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_HUDSON2_SMBUS } and { PCI_DEVICE(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS } These IDs make it easy to cross reference with the datasheet, and keeps the coupling between ACPI and the driver low. These drivers do not provide a mechanism for firmware (ACPI or DT) to specify which gpios are safe to use or how to use them. In contrast, the pinctrl-amd driver only mentions the newer KERNCZ platform name and uses ACPI for probing without disclosing any Family or Model numbers. pinctrl-amd applies to "AMD0030" and "AMDI0030" The ACPI HID matching makes it difficult to determine what family and model the driver applies to, or rather, I have not been able to find such a mapping of HIDs to family and model numbers. It's also impossible to guess an ACPI _HID that may or may not exist for the Family 16h Model 30h platform and even if I allocate a new HID for our ACPI implementation, that HID has little hope of being accepted into the mainline driver. I would like to extend the generically named, but very specifically implemented pinctrl-amd driver to also work on Family 16h, Model 30h (specifically the FT3b package), and I propose to use the PCI_DEVICE_ID_AMD_16H_M30H_NB_F3 symbol to probe for the device. Does this seem like a sensible way forward? Thanks! Andrew 1. http://support.amd.com/TechDocs/52740_16h_Models_30h-3Fh_BKDG.pdf 2. http://git.yoctoproject.org/cgit/cgit.cgi/meta-amd/tree/meta-steppeeagle/recipes-kernel/amd-gpio/files/gpio-amd.c 3. https://lkml.org/lkml/2015/6/20/202