From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org ([198.145.29.96]:43753 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753604AbbGVXpE (ORCPT ); Wed, 22 Jul 2015 19:45:04 -0400 Date: Wed, 22 Jul 2015 16:45:00 -0700 From: Stephen Boyd To: Andy Shevchenko Cc: linux-kernel@vger.kernel.org, heikki.krogerus@linux.intel.com, Greg Kroah-Hartman , Heiko Stuebner , linux-clk@vger.kernel.org Subject: Re: [PATCH v4 3/6] clk: fractional-divider: keep mwidth and nwidth internally Message-ID: <20150722234500.GF15042@codeaurora.org> References: <1436886723-111895-1-git-send-email-andriy.shevchenko@linux.intel.com> <1436886723-111895-4-git-send-email-andriy.shevchenko@linux.intel.com> <20150722004124.GE15042@codeaurora.org> <1437570566.8014.37.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1437570566.8014.37.camel@linux.intel.com> Sender: linux-clk-owner@vger.kernel.org List-ID: On 07/22, Andy Shevchenko wrote: > On Tue, 2015-07-21 at 17:41 -0700, Stephen Boyd wrote: > > On 07/14, Andy Shevchenko wrote: > > > diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk > > > -fractional-divider.c > > > index 7cfcc56..16f42ae 100644 > > > --- a/drivers/clk/clk-fractional-divider.c > > > +++ b/drivers/clk/clk-fractional-divider.c > > > @@ -128,9 +128,11 @@ struct clk > > > *clk_register_fractional_divider(struct device *dev, > > > > > > fd->reg = reg; > > > fd->mshift = mshift; > > > - fd->mmask = (BIT(mwidth) - 1) << mshift; > > > + fd->mwidth = mwidth; > > > + fd->mmask = GENMASK(mwidth - 1, 0) << mshift; > > > fd->nshift = nshift; > > > - fd->nmask = (BIT(nwidth) - 1) << nshift; > > > + fd->nwidth = nwidth; > > > + fd->nmask = GENMASK(nwidth - 1, 0) << nshift; > > > > Please do the shifts in the GENMASK. > > It's not optimal. Waste of performance. > > 32-bit case on 32-bit machine (similar to other cases on x86). > > a) GENMASK(x - 1, 0) << y > > movl $32, %ecx > subb 4(%esp), %cl > movl $-1, %eax > shrl %cl, %eax > movzbl 8(%esp), %ecx > sall %cl, %eax > ret > > b) GENMASK(x + y - 1, y) > > pushl %esi > pushl %ebx > movl $1, %edx > movzbl 12(%esp), %eax > movzbl 16(%esp), %esi > movl $-1, %ebx > subl %eax, %edx > movl %ebx, %eax > subl %esi, %edx > leal 31(%edx), %ecx > shrl %cl, %eax > movl %esi, %ecx > sall %cl, %ebx > andl %ebx, %eax > popl %ebx > popl %esi > ret > This is not hotpath code, so why do we care? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project