From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757361AbeDKThz (ORCPT ); Wed, 11 Apr 2018 15:37:55 -0400 Received: from mail-qt0-f195.google.com ([209.85.216.195]:45019 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756124AbeDKThu (ORCPT ); Wed, 11 Apr 2018 15:37:50 -0400 X-Google-Smtp-Source: AIpwx49YyZse/ylcv7P+3TqP1Du9v3TNShx4mkV0+7F8/tZrkiqSzFms2+pEMTbbFgjHKcs6r1TRSg== From: "Jingoo Han" To: "'Gustavo Pimentel'" , , , , , , Cc: , , References: <5181f7ffbb9d2889974c49d84e72042251adf8b6.1523266508.git.gustavo.pimentel@synopsys.com> <003001d3d128$39f3eaa0$addbbfe0$@gmail.com> In-Reply-To: Subject: Re: [PATCH v2 8/9] PCI: dwc: Small computation improvement Date: Wed, 11 Apr 2018 15:37:46 -0400 Message-ID: <000001d3d1cc$92706790$b75136b0$@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Content-Language: en-us Thread-Index: AQEaRjwvEF5/h3QMrbPVq+Y0x5xNJwIXxkZLAdaBFooA9hP2Z6VH6TYw Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, April 11, 2018 3:40 AM, Gustavo Pimentel wrote: > > Hi Jingoo, > > On 11/04/2018 01:01, Jingoo Han wrote: > > On Monday, April 9, 2018 5:41 AM, Gustavo Pimentel wrote: > >> > >> Replaces a simple division by 2 to a right shift rotation of 1 bit. > > > > It looks good. However, would you add a simple reason to the commit > > message? > > Sure. > > Can be this one? > > Probably any recent and decent compiler does this kind of substitution > in order to improve code performance. Nevertheless it's a coding good > practice whenever there is a division / multiplication by multiple of 2 > to replace it by the equivalent operation in this case, the shift > rotation. Yes, that's what I wanted. The most platforms using 'dwc' are based on ARM CPUs. So, the shift rotation can be better. Thank you. Best regards, Jingoo Han > > > > > Best regards, > > Jingoo Han > > > >> > >> Signed-off-by: Gustavo Pimentel > >> --- > >> Change v1->v2: > >> - Nothing changed, just to follow the patch set version. > >> > >> drivers/pci/dwc/pcie-designware-host.c | 8 ++++---- > >> 1 file changed, 4 insertions(+), 4 deletions(-) > >> > >> diff --git a/drivers/pci/dwc/pcie-designware-host.c > >> b/drivers/pci/dwc/pcie-designware-host.c > >> index 03e9b82..8e6fed4 100644 > >> --- a/drivers/pci/dwc/pcie-designware-host.c > >> +++ b/drivers/pci/dwc/pcie-designware-host.c > >> @@ -332,8 +332,8 @@ int dw_pcie_host_init(struct pcie_port *pp) > >> > >> cfg_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, > >> "config"); > >> if (cfg_res) { > >> - pp->cfg0_size = resource_size(cfg_res) / 2; > >> - pp->cfg1_size = resource_size(cfg_res) / 2; > >> + pp->cfg0_size = resource_size(cfg_res) >> 1; > >> + pp->cfg1_size = resource_size(cfg_res) >> 1; > >> pp->cfg0_base = cfg_res->start; > >> pp->cfg1_base = cfg_res->start + pp->cfg0_size; > >> } else if (!pp->va_cfg0_base) { > >> @@ -377,8 +377,8 @@ int dw_pcie_host_init(struct pcie_port *pp) > >> break; > >> case 0: > >> pp->cfg = win->res; > >> - pp->cfg0_size = resource_size(pp->cfg) / 2; > >> - pp->cfg1_size = resource_size(pp->cfg) / 2; > >> + pp->cfg0_size = resource_size(pp->cfg) >> 1; > >> + pp->cfg1_size = resource_size(pp->cfg) >> 1; > >> pp->cfg0_base = pp->cfg->start; > >> pp->cfg1_base = pp->cfg->start + pp->cfg0_size; > >> break; > >> -- > >> 2.7.4 > >> > > > > > > Regards, > Gustavo