Hi > -----Original Message----- > From: Tim Harvey [mailto:tharvey@xxxxxxxxxxxxx] > Sent: Friday, June 27, 2014 8:29 AM > To: Guo Shawn-R65073; Zhu Richard-R65037 > Cc: Fabio Estevam; Bjorn Helgaas; Marek Vašut; David Müller (ELSOFT AG); > Sascha Hauer; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; > Estevam Fabio-R49496 > Subject: Re: [RFC] PCI: pci-imx6: Add delay to workaround kernel hang > > On Wed, Jun 25, 2014 at 10:49 PM, Shawn Guo <shawn.guo@xxxxxxxxxxxxx> wrote: > > On Thu, Jun 26, 2014 at 12:43:19AM -0300, Fabio Estevam wrote: > >> On Thu, Jun 26, 2014 at 12:12 AM, Shawn Guo <shawn.guo@xxxxxxxxxxxxx> wrote: > >> > On Tue, Jun 24, 2014 at 04:18:27PM -0300, Fabio Estevam wrote: > >> >> From: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> > >> >> > >> >> When the mx6 PCI conctroller is initialized in the bootloader we > >> >> see a kernel hang inside imx6_add_pcie_port(). > >> >> > >> >> Adding a 30ms delay allows the kernel to boot. > >> > > >> > We may not want to add a random delay into the driver before we > >> > understand the root cause of the issue. > >> > >> Yes, that's why I sent this as RFC and also explained it below the > >> --- line that I am actually trying to get some help with this issue. > >> > >> > > >> > Do you see this issue with FSL kernel? > >> > >> Yes, it also hangs. > >> > >> It is reproducible in 100% of the boots. Just need to use mainline > >> U-boot (which has PCI driver enabled by default). > >> I am using an Intel Wifi 7260 PCI card. This was also reported by > >> other folks in the U-boot list. > > > > Richard, > > > > Can you schedule some time to look at this issue? I think it will > > come to us sooner or later if any our customer enables PCIe before > > launching kernel? > > > > Shawn > > > [Richard] I did the tests refer to this use-case, enable imx6 pcie on both u-boot and kernel, and I encounter the system hang too. Here are the latest updates and some clues from my side: - About 200us delay is required after the ltssm_en is set to be '1' at my side. Otherwise, system would be hang when driver access the pcie_phy_debug_r1 to check the link is up or not. - After that, system hang when rc trying to access the cfg space of ep device, Although the pcie link had been setup and I don't have know the root cause yet. - The kernel can boot up successfully, when I mask the cfg read/write call-back in pcie-designware.c Driver for debug purpose. Note: The sequence of the pcie initialization should be adjusted refer to the newly discovered bug(pcie link maybe rarely random down after the system warm-reset). * Ref_ssp_en(bit16 of gpr1 register) should be set after the pcie others clks are enable. Enable pcie related clks --> delay for about ~10us waiting for the clks stable-->set ref_ssp_en(bit16 of gpr1 register). Debug is still on-going. > Shawn / Richard, > > I am also affected by this issue on IMX6 boards that I support. If I enable > PCI in the bootloader I see similar hangs. > > I have the following hardware configurations on my bench: > 1. IMX6DL + i210 (same PCI setup as Fabio's above, but DL instead of Q) > 2. IMX6Q + ath9k device > 3. IMX6DL + PLX PEX860x PCIe-to-PCIe bridge with various devices behind the > bridge, using a clock buffer from IMX6 PCIe clock > 4. IMX6Q + PLX PEX860x PCIe-to-PCIe bridge with various devices behind the > bridge, using a clock buffer from IMX6 PCIe clock > 5. IMX6Q + PLX PEX860x PCIe-to-PCIe bridge with various devices behind the > bridge using a clock generator (always on, ignoring the PCIe clock) > > For all of the above I have no PCI issues using 3.14/3.15/3.16-rc2/vendor > 3.10.17_1.0.0_ga unless I enable PCI in the bootloader. When I do so, all of > the above configurations hang somewhere around PCI init/enumeration. The same > occurs with the most recent vendor kernel 3.10.17_1.0.0_ga kernel (works when > PCI is disabled in the bootloader, hangs otherwise). > > When I apply Fabio's patch above to the 3.16-rc2 kernel I find that scenarios > #4 and #5 above then work, #3 boots but the PLX bridge fails all config cycles > (0xff's), #2 boots but with no PCIe link, and #1 above still hangs. Previously, > when I have dug into this particular 'hang' issue on 3.15 I found that the > delay needed to be between > imx6_pcie_probe() requesting and asserting reset_gpio low, and before setting > IOMUX_GPR1:18 to power down the PCIe PHY (note here, that the PHY is currently > enabled in the bootloader when PCI is enabled there). > > When I apply Fabio's patch above to the most recent vendor kernel > 3.10.17_1.0.0_ga I still hang in all cases. > > So while I agree there is something horribly wrong with IMX6 PCI still, I > don't think Fabio's patch is the right solution and I don't have anything > better at this point in time. I'm happy to share any hardware with anyone that > can work through this issue. > > Thanks, > > Tim Best Regards Richard Zhu ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
