From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH 1/6] bitops: Introduce the the for_each_set_clump macro Date: Fri, 24 Apr 2020 19:34:10 +0300 Message-ID: <20200424163410.GD185537@smile.fi.intel.com> References: <20200424122521.GA5552@syed> <20200424141037.ersebbfe7xls37be@wunner.de> <20200424150058.xadjxaga3csh3br6@wunner.de> <20200424150828.GA5034@icarus> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mga03.intel.com ([134.134.136.65]:11407 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727123AbgDXQeK (ORCPT ); Fri, 24 Apr 2020 12:34:10 -0400 Content-Disposition: inline In-Reply-To: <20200424150828.GA5034@icarus> Sender: linux-arch-owner@vger.kernel.org List-ID: To: William Breathitt Gray Cc: Lukas Wunner , Syed Nayyar Waris , akpm@linux-foundation.org, arnd@arndb.de, Linus Walleij , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org On Fri, Apr 24, 2020 at 11:09:26AM -0400, William Breathitt Gray wrote: > On Fri, Apr 24, 2020 at 05:00:58PM +0200, Lukas Wunner wrote: > > On Fri, Apr 24, 2020 at 08:22:38PM +0530, Syed Nayyar Waris wrote: > > > On Fri, Apr 24, 2020 at 7:40 PM Lukas Wunner wrote: > > > > On Fri, Apr 24, 2020 at 05:55:21PM +0530, Syed Nayyar Waris wrote: ... > > > So, this function preserves the behaviour of earlier > > > bitmap_set_value8() function and also adds extra functionality to > > > that. > > > > Please leave drivers as is which use exclusively 8-bit accesses, > > e.g. gpio-max3191x.c and gpio-74x164.c. I'm fearing a performance > > regression if your new generic variant is used. They work perfectly > > fine the way they are and I don't see any benefit this series may have > > for them. > > > > If there are other drivers which benefit from the flexibility of your > > generic variant then I'm not opposed to changing those. > We can leave of course bitmap_set_value8 alone, but for 8-bit values the > difference in latency I suspect is primarily due to the conditional test > for the word boundaries. This latency is surely overshadowed by the I/O > latency of the GPIO drivers, so I don't think there's much harm in > changing those to use the generic function when the bottleneck will not > be due to the bitmap_set_value/bitmap_get_value operations. Okay, how many new (non-8-bit) users this will target? -- With Best Regards, Andy Shevchenko