From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH v2] net: smc91x: fix SMC accesses Date: Sun, 28 Aug 2016 23:46:35 -0400 (EDT) Message-ID: <20160828.234635.224236136235372450.davem@davemloft.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: arnd@arndb.de, nico@fluxnic.net, netdev@vger.kernel.org, realmz6@gmail.com, adi-buildroot-devel@lists.sourceforge.net, haojian.zhuang@gmail.com, linux-arm-kernel@lists.infradead.org, robert.jarzmik@free.fr, daniel@zonque.org To: rmk+kernel@armlinux.org.uk Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: netdev.vger.kernel.org From: Russell King Date: Sat, 27 Aug 2016 17:33:03 +0100 > Commit b70661c70830 ("net: smc91x: use run-time configuration on all ARM > machines") broke some ARM platforms through several mistakes. Firstly, > the access size must correspond to the following rule: > > (a) at least one of 16-bit or 8-bit access size must be supported > (b) 32-bit accesses are optional, and may be enabled in addition to > the above. > > Secondly, it provides no emulation of 16-bit accesses, instead blindly > making 16-bit accesses even when the platform specifies that only 8-bit > is supported. > > Reorganise smc91x.h so we can make use of the existing 16-bit access > emulation already provided - if 16-bit accesses are supported, use > 16-bit accesses directly, otherwise if 8-bit accesses are supported, > use the provided 16-bit access emulation. If neither, BUG(). This > exactly reflects the driver behaviour prior to the commit being fixed. > > Since the conversion incorrectly cut down the available access sizes on > several platforms, we also need to go through every platform and fix up > the overly-restrictive access size: Arnd assumed that if a platform can > perform 32-bit, 16-bit and 8-bit accesses, then only a 32-bit access > size needed to be specified - not so, all available access sizes must > be specified. > > This likely fixes some performance regressions in doing this: if a > platform does not support 8-bit accesses, 8-bit accesses have been > emulated by performing a 16-bit read-modify-write access. > > Tested on the Intel Assabet/Neponset platform, which supports only 8-bit > accesses, which was broken by the original commit. > > Fixes: b70661c70830 ("net: smc91x: use run-time configuration on all ARM machines") > Signed-off-by: Russell King Applied and queued up for -stable, thanks Russell.