linux-kernel - [PATCH v8 8/9] PCI: dwc: Small computation improvement

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <a0bb1eb13d2f2a156c3b5a99d6140c07b6b56fe4.1524829928.git.gustavo.pimentel@synopsys.com>
Date:   Fri, 27 Apr 2018 13:00:03 +0100
From:   Gustavo Pimentel <gustavo.pimentel@...opsys.com>
To:     bhelgaas@...gle.com, lorenzo.pieralisi@....com,
        Joao.Pinto@...opsys.com, jingoohan1@...il.com, kishon@...com,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, gustavo.pimentel@...opsys.com
Subject: [PATCH v8 8/9] PCI: dwc: Small computation improvement

Replace a division by 2 operation for 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 <gustavo.pimentel@...opsys.com>
Acked-by: Jingoo Han <jingoohan1@...il.com>
Acked-by: Joao Pinto <jpinto@...opsys.com>
---
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.
Changes v5->v6:
 - Nothing changed, just to follow the patch set version.
Changes v6->v7:
 - Nothing changed, just to follow the patch set version.
Changes v7->v8:
 - Patch description rework for an imperative verbal mode.

 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;
-- 
2.7.4