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Message-ID: <CA+P7+xr1N+X5DyPwNpWUtfqr9U4pLL9bMoB1wkBdf2K9n6cxKw@mail.gmail.com> Date: Mon, 2 Apr 2018 17:30:54 -0700 From: Jacob Keller <jacob.keller@...il.com> To: Bjorn Helgaas <helgaas@...nel.org> Cc: Tal Gilboa <talgi@...lanox.com>, Tariq Toukan <tariqt@...lanox.com>, Jacob Keller <jacob.e.keller@...el.com>, Ariel Elior <ariel.elior@...ium.com>, Ganesh Goudar <ganeshgr@...lsio.com>, Jeff Kirsher <jeffrey.t.kirsher@...el.com>, everest-linux-l2@...ium.com, intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org Subject: Re: [PATCH v5 03/14] PCI: Add pcie_bandwidth_capable() to compute max supported link bandwidth On Mon, Apr 2, 2018 at 7:05 AM, Bjorn Helgaas <helgaas@...nel.org> wrote: > +/* PCIe speed to Mb/s reduced by encoding overhead */ > +#define PCIE_SPEED2MBS_ENC(speed) \ > + ((speed) == PCIE_SPEED_16_0GT ? (16000*(128/130)) : \ > + (speed) == PCIE_SPEED_8_0GT ? (8000*(128/130)) : \ > + (speed) == PCIE_SPEED_5_0GT ? (5000*(8/10)) : \ > + (speed) == PCIE_SPEED_2_5GT ? (2500*(8/10)) : \ > + 0) > + Should this be "(speed * x ) / y" instead? wouldn't they calculate 128/130 and truncate that to zero before multiplying by the speed? Or are compilers smart enough to do this the other way to avoid the losses? Thanks, Jake
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