<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - [BYT LPSS backlight] Acer Aspire Switch 10 backlight control" href="https://bugs.freedesktop.org/show_bug.cgi?id=90075#c18">Comment # 18</a> on <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - [BYT LPSS backlight] Acer Aspire Switch 10 backlight control" href="https://bugs.freedesktop.org/show_bug.cgi?id=90075">bug 90075</a> from <a class="email" href="mailto:darlor@seznam.cz" title="darlor@seznam.cz">darlor@seznam.cz</a> <pre>Created <a href="attachment.cgi?id=134602" name="attach_134602" title="3 dmesg with different pci kernel parameters">attachment 134602</a> <a href="attachment.cgi?id=134602&action=edit" title="3 dmesg with different pci kernel parameters">[details]</a> 3 dmesg with different pci kernel parameters Hello everyone, I think (hope) I identified underlying problem why PCI device 8086-0F08 PWM Controller is not detected. (without it backlight will not work) But now I'm stuck because I`m not familiar with PCI Bus, e820 etc... and to be honest I don`t exactly know what I`m looking at... First let me explain my thoughts: On Windows using SIV - System Information Viewer I can see: Bus-Numb-Fun IRQ Vendor-Dev-Sub_OEM-Rev Class (0:63) Vendor and Device Description 0-00-0 8086-0F00-09281025-0F Host Bridge Intel Atom SSA-CUnit 0-02-0 8086-0F31-09281025-0F VGA Controller Intel Atom Gen7 [GPU-0] 0-20-0 8086-0F35-09281025-0F XHCI Controller Intel Atom USB xHCI Host Cntrlr 0-26-0 8086-0F18-09281025-0F Other Encryption Intel Atom SEC 0-30-1 8086-0F08-09281025-0F Other Interface Intel Atom LPIO1 PWM Controller 0-31-0 8086-0F1C-09281025-0F ISA Bridge Intel Atom Power Control Unit 0 None of these devices is mentioned in DSDT. (at least by Vendor-Device code) lspci on linux shows something like: 00:00.0 0600: 8086:0f00 Host bridge: Intel Corporation... 00:02.0 0300: 8086:0f31 VGA compatible controller... 00:14.0 0c03: 8086:0f35 USB controller... 00:1a.0 1080: 8086:0f18 Encryption controller... 00:1f.0 0601: 8086:0f1c ISA bridge... ACPI-IDs are same, but PWM controller is missing. So I think that PWM controller is connected to PCI bus. (CONFIG_PWM_LPSS_PCI must be enabled so pwm-lpss-pci.ko module can be used). But why this PCI device is not detected? Lets have a look on kernel messages in file 'dmesg_nothing_special' Lines that caught my eyes: PCI: MMCONFIG for domain 0000 [bus 00-3f] at [mem 0xe0000000-0xe3ffffff] (base 0xe0000000) PCI: not using MMCONFIG PCI: Using configuration type 1 for base access PCI: MMCONFIG for domain 0000 [bus 00-3f] at [mem 0xe0000000-0xe3ffffff] (base 0xe0000000) [Firmware Info]: PCI: MMCONFIG at [mem 0xe0000000-0xe3ffffff] not reserved in ACPI motherboard resources PCI: not using MMCONFIG PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) acpi PNP0A08:00: fail to add MMCONFIG information, can't access extended PCI configuration space under this bridge. Expanded resource Reserved due to conflict with PCI Bus 0000:00 So I googled a little bit and added kernel parameter "memmap=64M\$0xe0000000" so the extended PCI configuration space 0x00000000e0000000-0x00000000e3ffffff is reserved. (don't forget that $ needs to be escaped with '\' or '\\\' in /etc/default/grub). This dmesg is in file 'dmesg_memmap_64M_0xe0000000' [<a href="https://www.centos.org/forums/viewtopic.php?t=53903">https://www.centos.org/forums/viewtopic.php?t=53903</a>] and I got: PCI: MMCONFIG for domain 0000 [bus 00-3f] at [mem 0xe0000000-0xe3ffffff] (base 0xe0000000) PCI: MMCONFIG at [mem 0xe0000000-0xe3ffffff] reserved in E820 PCI: Using configuration type 1 for base access PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) acpi PNP0A08:00: [Firmware Info]: MMCONFIG for domain 0000 [bus 00-3f] only partially covers this bridge Expanded resource Reserved due to conflict with PCI Bus 0000:00 So, MMCONFIG only partially covers extended configuration for this bridge. I don`t exactly know what it means. Only that made sense was to add pci=nocrs, but it did not solve a thing except that line: Expanded resource Reserved due to conflict with PCI Bus 0000:00 is not in dmesg anymore. This dmesg is in file 'dmesg_memmap_64M_0xe0000000_pci_nocrs'. Could someone please confirm, that it make sense and/or provide some tips how to go forward? Thanks ('cut -d" " -f6-' < dmesg > graphical_diff makes dmesgs very easy to compare :-) )</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> </ul> </body> </html>