Date: Sun, 15 Dec 2013 07:05:35 +0400 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Anton Yuzhaninov <citrin@citrin.ru> Cc: svn-src-all@freebsd.org Subject: Re: svn commit: r259150 - head/sys/dev/cxgbe Message-ID: <20131215030535.GC29088@glebius.int.ru> In-Reply-To: <52A840D4.9020407@citrin.ru> References: <201312100007.rBA074Qq055579@svn.freebsd.org> <20131210192650.GK4615@FreeBSD.org> <52A76BBE.5030903@FreeBSD.org> <52A840D4.9020407@citrin.ru>
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Anton, On Wed, Dec 11, 2013 at 02:39:16PM +0400, Anton Yuzhaninov wrote: A> On 12/10/13 23:30, Alexander Motin wrote: A> >> A> New Revision: 259150 A> >> A> URL: http://svnweb.freebsd.org/changeset/base/259150 A> >> A> A> >> A> Log: A> >> A> Print out the full PCIe link negotiation during dmesg. A> >> A> >> Shouldn't this be done with common code for all drivers A> >> on PCI bus(es)? A> >> A> >> This is definitely useful for all devices, not to cxgbe(4) only. A> > A> > Why not just read `pciconf -lc` output for that? A> A> 1. pciconf output is cryptic. At least units of measurement should be added. A> A> e. g. current output: A> A> cap 10[a0] = PCI-Express 2 endpoint max data 256(512) FLR link x4(x4) A> speed 5.0(5.0) ASPM disabled(L0s/L1) A> A> better to print like: A> A> cap 10[a0] = PCI-Express 2 endpoint max data 256(512) FLR link width x4(x4) A> speed 5.0 GT/s (5.0 GT/s) ASPM disabled(L0s/L1) A> A> 2. It is not obvious for system administrators, that pciconf should be used to A> inquire link speed. This feature is not documented in handbook or man pages. A> A> 3. I agree, that adding more noise to dmesg is not good, but if current A> bandwidth is not enough for optimal work of the device - error should be printed A> in dmesg. A> A> Example can be found in sys/dev/ixgbe/ixgbe.c A> A> if ((hw->bus.width <= ixgbe_bus_width_pcie_x4) && A> (hw->bus.speed == ixgbe_bus_speed_2500)) { A> device_printf(dev, "PCI-Express bandwidth available" A> " for this card\n is not sufficient for" A> " optimal performance.\n"); A> device_printf(dev, "For optimal performance a x8 " A> "PCIE, or x4 PCIE 2 slot is required.\n"); A> } A> A> 4. Similar speed check will be useful for many devices, not only for ixgbe or A> cxgbe and should be done in some generic way. I think, that if you submit patches, that implement above features, someone will take them and commit :) -- Totus tuus, Glebius.
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