From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753858Ab2DWGxi (ORCPT ); Mon, 23 Apr 2012 02:53:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55887 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752539Ab2DWGxh (ORCPT ); Mon, 23 Apr 2012 02:53:37 -0400 Date: Sun, 22 Apr 2012 23:55:06 -0700 From: Andrew Morton To: Wolfram Sang Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Shawn Guo , Huang Shijie Subject: Re: [PATCH V2 1/3] lib: add support for stmp-style devices Message-Id: <20120422235506.d3377f0e.akpm@linux-foundation.org> In-Reply-To: <1332368519-22660-2-git-send-email-w.sang@pengutronix.de> References: <1332368519-22660-1-git-send-email-w.sang@pengutronix.de> <1332368519-22660-2-git-send-email-w.sang@pengutronix.de> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Mar 2012 23:21:57 +0100 Wolfram Sang wrote: > MX23/28 use IP cores which follow a register layout I have first seen on > STMP3xxx SoCs. In this layout, every register actually has four u32: > > 1.) to store a value directly > 2.) a SET register where every 1-bit sets the corresponding bit, > others are unaffected > 3.) same with a CLR register > 4.) same with a TOG (toggle) register > > Also, the 2 MSBs in register 0 are always the same and can be used to reset > the IP core. > > All this is strictly speaking not mach-specific (but IP core specific) and, > thus, doesn't need to be in mach-mxs/include. At least, mx6 and mx50 also > utilize IP cores following this stmp-style. So: > > Introduce a stmp-style device, put the code and defines for that in a public > place (lib/), and let drivers for stmp-style devices select that code. > To avoid regressions and ease reviewing, the actual code is simply copied from > mach-mxs. It definately wants updates, but those need a seperate patch series. > > Voila, mach dependency gone, reusable code introduced. Note that I didn't > remove the duplicated code from mach-mxs yet, first the drivers have to be > converted. > > ... > > include/linux/stmp_device.h | 20 +++++++++++ > lib/Kconfig | 3 ++ > lib/Makefile | 2 + > lib/stmp_device.c | 80 +++++++++++++++++++++++++++++++++++++++++++ It's good that this is being presented as library code, rather than being buried in some device-specific directory then copied and pasted ten times. But ./lib/ does seem rather a strange place for it. Perhaps we need a drivers/lib/ or something. We can use ./lib/ for now - it can always be moved later on. > --- /dev/null > +++ b/lib/stmp_device.c The functions in this file look terribly racy on SMP, or even with preemption or interrupts. What happens if two CPUs or threads run stmp_reset_block() against the same device at the same time? Perhaps the caller is supposed to prevent that, and the documentation which isn't there forgot to mention it ;) From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org (Andrew Morton) Date: Sun, 22 Apr 2012 23:55:06 -0700 Subject: [PATCH V2 1/3] lib: add support for stmp-style devices In-Reply-To: <1332368519-22660-2-git-send-email-w.sang@pengutronix.de> References: <1332368519-22660-1-git-send-email-w.sang@pengutronix.de> <1332368519-22660-2-git-send-email-w.sang@pengutronix.de> Message-ID: <20120422235506.d3377f0e.akpm@linux-foundation.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 21 Mar 2012 23:21:57 +0100 Wolfram Sang wrote: > MX23/28 use IP cores which follow a register layout I have first seen on > STMP3xxx SoCs. In this layout, every register actually has four u32: > > 1.) to store a value directly > 2.) a SET register where every 1-bit sets the corresponding bit, > others are unaffected > 3.) same with a CLR register > 4.) same with a TOG (toggle) register > > Also, the 2 MSBs in register 0 are always the same and can be used to reset > the IP core. > > All this is strictly speaking not mach-specific (but IP core specific) and, > thus, doesn't need to be in mach-mxs/include. At least, mx6 and mx50 also > utilize IP cores following this stmp-style. So: > > Introduce a stmp-style device, put the code and defines for that in a public > place (lib/), and let drivers for stmp-style devices select that code. > To avoid regressions and ease reviewing, the actual code is simply copied from > mach-mxs. It definately wants updates, but those need a seperate patch series. > > Voila, mach dependency gone, reusable code introduced. Note that I didn't > remove the duplicated code from mach-mxs yet, first the drivers have to be > converted. > > ... > > include/linux/stmp_device.h | 20 +++++++++++ > lib/Kconfig | 3 ++ > lib/Makefile | 2 + > lib/stmp_device.c | 80 +++++++++++++++++++++++++++++++++++++++++++ It's good that this is being presented as library code, rather than being buried in some device-specific directory then copied and pasted ten times. But ./lib/ does seem rather a strange place for it. Perhaps we need a drivers/lib/ or something. We can use ./lib/ for now - it can always be moved later on. > --- /dev/null > +++ b/lib/stmp_device.c The functions in this file look terribly racy on SMP, or even with preemption or interrupts. What happens if two CPUs or threads run stmp_reset_block() against the same device at the same time? Perhaps the caller is supposed to prevent that, and the documentation which isn't there forgot to mention it ;)