From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988AbbJWO0w (ORCPT ); Fri, 23 Oct 2015 10:26:52 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:41498 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbbJWO0u (ORCPT ); Fri, 23 Oct 2015 10:26:50 -0400 Message-ID: <562A4372.4040008@ti.com> Date: Fri, 23 Oct 2015 10:25:54 -0400 From: Murali Karicheri Organization: Texas Instruments User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Arnd Bergmann , Loc Ho CC: Russell King - ARM Linux , KISHON VIJAY , WingMan Kwok , Rob Herring , , Mark Rutland , Ian Campbell , , , , , "devicetree@vger.kernel.org" , Linux Kernel Mailing List , , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v3 0/2] Common SerDes driver for TI's Keystone Platforms References: <1445432201-16007-1-git-send-email-w-kwok2@ti.com> <56295B9E.9030201@ti.com> <3702663.07h6YO0UjY@wuerfel> In-Reply-To: <3702663.07h6YO0UjY@wuerfel> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/23/2015 05:17 AM, Arnd Bergmann wrote: > On Thursday 22 October 2015 15:27:05 Loc Ho wrote: >>> >>> phy-xgene.c >>> ----------- >>> >>> Looking at other drivers under drivers/phy, I could find phy-xgene.c which >>> is close Keystone SerDes driver (. This is called APM X-Gene Multi-Purpose >>> PHY driver. It defines following mode per the driver code >>> >>> MODE_SATA = 0, /* List them for simple reference */ >>> MODE_SGMII = 1, >>> MODE_PCIE = 2, >>> MODE_USB = 3, >>> MODE_XFI = 4, >>> >>> But seems to support only MODE_SATA. From the code, it appears, this driver >>> is expected to be enhanced in the future to support additional modes. I have >>> copied the author to this email to participate in this discussion. >> >> Let me comment on this APM X-Gene driver. This driver is dead and >> won't be supported in near or foreseeable future. And someday, it will >> be ripped out. Based on experience, this solution (having PHY driver >> in Linux) can't be supported across boards and etc as it is just too >> much maintenance. And therefore, we followed Arnd B guidance and move >> all this into the boot loader. From Linux or OS perspective, it only >> cares about the interface in which its interface with. This is just >> your reference and may be this will help you as well. > > This depends a lot on the use case. If the chip is only used on server > parts that have a real firmware and you can deliver bug fixes for the > firmware if necessary, it's always best to do as much of the setup as > possible there, and let Linux see a simplified view of the hardware. > > However, for embedded systems that tend to ship with a minimal binary > bootloader and no way to update that as an end-user, we rely on Linux > to know about all the hardware that requires some form of setup, which > is why we have all sorts of drivers and frameworks in the kernel that > a server can easily ignore. > > While keystone can show up in servers that won't use this driver, my > impression is that its main market is actually in embedded space. It is in embedded space predominantly. From our experience, this has to be a Linux driver and moving this to boot loader doesn't make sense. Murali > > Arnd > -- Murali Karicheri Linux Kernel, Keystone