From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752958AbeDQTFU (ORCPT ); Tue, 17 Apr 2018 15:05:20 -0400 Received: from smtprelay2.synopsys.com ([198.182.60.111]:48352 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752733AbeDQTFR (ORCPT ); Tue, 17 Apr 2018 15:05:17 -0400 Subject: Re: [PATCH v5 09/10] PCI: dwc: Small computation improvement To: Gustavo Pimentel , , , , , , , CC: , , References: <4fc069a2b82cc7a3790bc528a6b67636654a3a35.1523973931.git.gustavo.pimentel@synopsys.com> From: Joao Pinto Message-ID: Date: Tue, 17 Apr 2018 20:05:11 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <4fc069a2b82cc7a3790bc528a6b67636654a3a35.1523973931.git.gustavo.pimentel@synopsys.com> Content-Type: text/plain; charset="utf-8" Content-Language: pt-PT Content-Transfer-Encoding: 8bit X-Originating-IP: [10.107.15.26] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Às 3:34 PM de 4/17/2018, Gustavo Pimentel escreveu: > Replaces a simple division by 2 to a right shift rotation of 1 bit. > > 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. > > Signed-off-by: Gustavo Pimentel > --- > Change v1->v2: > - Nothing changed, just to follow the patch set version. > Change v2->v3: > - Nothing changed, just to follow the patch set version. > Changes v3->v4: > - Added a small explication to the log description. > Changes v4->v5: > - 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 5a23f78..fc55fde 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; > Thanks Gustavo! Acked-by: Joao Pinto