From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Farnsworth Subject: Re: [Intel-gfx] GPU RC6 breaks PCIe to PCI bridge connected to CPU PCIe slot on SandyBridge systems Date: Fri, 19 Oct 2012 18:06:41 +0100 Message-ID: <2244094.6Dmq15viKH@f17simon> References: <1704067.2NCOGYajHN@f17simon> <3896332.1fABn9rFR8@f17simon> <2233216.7bl6QCud67@f17simon> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart4058091.mohbLKXv11"; micalg="pgp-sha1"; protocol="application/pgp-signature" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <2233216.7bl6QCud67@f17simon> Sender: linux-pci-owner@vger.kernel.org To: intel-gfx@lists.freedesktop.org Cc: Daniel Vetter , bhelgaas@google.com, linux-pci@vger.kernel.org, linux-media@vger.kernel.org, mchehab@infradead.org List-Id: intel-gfx@lists.freedesktop.org --nextPart4058091.mohbLKXv11 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Friday 19 October 2012 17:10:17 Simon Farnsworth wrote: > Mauro, Linux-Media > > I have an issue where an SAA7134-based TV capture card connected via a PCIe to > PCI bridge chip works when the GPU is kept out of RC6 state, but sometimes > "skips" updating lines of the capture when the GPU is in RC6. We've confirmed > that a CX23418 based chip doesn't have the problem, so the question is whether > the SAA7134 and the saa7134 driver are at fault, or whether it's the PCIe bus. > > This manifests as a regression, as I had no problems with kernel 3.3 (which > never enabled RC6 on the Intel GPU), but I do have problems with 3.5 and with > current Linus git master. I'm happy to try anything, > > I've attached lspci -vvxxxxx output (suitable for feeding to lspci -F) for > when the corruption is present (lspci.faulty) and when it's not > (lspci.working). The speculation is that the SAA7134 is somehow more > sensitive to the changes in timings that RC6 introduces than the CX23418, and > that someone who understands the saa7134 driver might be able to make it less > sensitive. > And timings are definitely the problem; I have a userspace provided pm_qos request asking for 0 exit latency, but I can see CPU cores entering C6. I'll take this problem to an appropriate list. There is still be a bug in the SAA7134 driver, as the card clearly wants a pm_qos request when streaming to stop the DMA latency becoming too high; this doesn't directly affect me, as my userspace always requests minimal DMA latency anyway, so consider this message as just closing down the thread for now, and as a marker for the future (if people see such corruption, the saa7134 driver needs a pm_qos request when streaming that isn't currently present). -- Simon Farnsworth Software Engineer ONELAN Ltd http://www.onelan.com --nextPart4058091.mohbLKXv11 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQEcBAABAgAGBQJQgYimAAoJEIKsye9/dtRWos4H/jaQFkVCaajyMsUJvu7Doe3/ 6XxuEdETC/4YX4SCzbTfRUQ7NaKHP/0H0YxeRQdsFnU640QLApQ8RrRKBZ5EUD2Y xG36GKSWyGxJ9MLnSEDFy6z3xL8qRkq9oTASkDkKshP/oZsZDwIooqEUy/QhX3Sb jUxumcyNsfbrcApFhNOkzDavl7n/KdjB0NuwZh7+ZUnljYHqse9dGpsrovPPoJzA KfvXzzI672IPHEGPtpkbUP3/eZrcJ71Te+JXeWf2COx39DtuWCSZHu3+IpT5dYEk bx1CuYA+kw6WxPBhOC3hk9Dptryj0JbBCtAdLvT7xrhPw1sS+dUsEvz/LRxr3m0= =QFbN -----END PGP SIGNATURE----- --nextPart4058091.mohbLKXv11--