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| − | == Overview ==
| + | #REDIRECT [[CM-X270: Linux: Kernel]] |
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| − | Linux kernel for CM-X270 modules provides support for on-board peripherals. Current support coverage is specified at [http://www.compulab.co.il/x270cm/html/x270-os-support.htm O/S support coverage map] page.
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| − | CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly on CM-X270 modules.
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| − | == Building Linux kernel for CM-X270 ==
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| − | Instructions for building Linux kernel for CM-X270 can be found [[Linux_Development_for_XScale_modules#Building the Linux kernel for CM-X270 | here]].
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| − | == CM-X270 specific additions and changes to Linux kernel 2.6.16 ==
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| − | === Basic Platform Support ===
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| − | The CM-X270 platform basic support is implemented in the {{filename|linux/arch/arm/mach-pxa/cm-x270.c}}. This file includes registration of the devices integrated in the PXA270 SoC, definitions of platform-specific configuration of these devices, platfrom-specific power management code and static mapping for memory mapped IO. This file also includes several routines needed for proper operation of the PCI bridge.
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| − | === PCI support ===
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| − | The board support for CM-X270 introduces driver for ITE 8152 companion chip and platform specific drivers for proper initialization of ITE 8152 on the CM-X270. The bridge driver implementation resides in {{filename|linux/arch/arm/mach-pxa/it8152.[ch]}}, parts of the CM-X270 specific initialization code are in {{filename|linux/arch/arm/mach-pxa/cm-x270-pci.c}}. There are also changes in {{filename|linux/arch/arm/kernel/bios32.c}} that are needed to use the ITE 8152 PCI bridge.
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| − | ==== PCI Ethernet Cards ====
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| − | The CompuLab stock kernel does not include built-in support for PCI Ethernet cards. A driver for popular RealTek 8139 card is available as loadable kernel module in [http://www.compulab.co.il/x270cm/download/x270-linux-img.zip Debian Linux for CM-X270] package. The module is called {{parameter|8139too}} and can be enabled using
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| − | <pre>
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| − | modprobe 8139too
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| − | </pre>
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| − | | |
| − | === Sound and Touchsreen ===
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| − | UCB1400 AC97 codec with inetgrated touchscreen has several registers, that are not present in AC97 standard. We added initialization of some of these registers and exposure of these registers to user space. This change can be found in {{filename|linux/sound/pci/ac97/ac97_patch.[ch]}}
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| − | The touchscreen controller driver for UCB1400 is taken from patch [http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=3075/2 3075/2] in the [http://www.arm.linux.org.uk/developer/patches/ ARM Linux patch system] and slightly modified to suit CM-X270 hardware configuration.
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| − | Both audio and touchscreen drivers are modularized if you use default CM-X270 configuration. The following commands enable audio support and touchscreen support respectively:
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| − | <pre>
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| − | modprobe snd-pxa2xx-ac97
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| − | modprobe ucb1x00-ts
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| − | </pre>
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| − | Note, that enabling touchscreen driver without AC97 controller driver is meaningless, since {{parameter|ucb1x00-ts}} driver uses AC97 bus to access the touchscreen device.
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| − | More information about Linux audio subsystem can be found at [http://www.alsa-project.org http://www.alsa-project.org]
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| − | ==== AC'97 and PCI interaction ====
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| − | {{note|
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| − | The following note is relevant only for cards with 'B' option and without 'A' or 'AT' options.
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| − | }}
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| − | CM-X270 contains local bus arbitration logic needed to arbiter bus accesses between the CPU and PCI bridge. This arbitration logic and AC97 controller share the same input clock. Linux AC97 driver tests whether there's an audio codec attached to the AC97 bus. If the driver does not find a codec, it disables PXA270 AC97 controller, and its clock altogether. Disabling this clock, in turn, disables the local bus arbitration, and makes PCI bridge useless.
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| − | To avoid such unpleasant situation we'd recommend not to enable sound drivers, unless you need them.
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| − | === NAND flash ===
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| − | CompuLab provides proprietary driver for on-board NAND flash. This driver emulates block device and provides wear-leveling for the flash. The driver uses the same NAND flash layout as the ARMMon bootloader.
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| − | Starting at kernel release at October 12, 2006, we also included MTD driver for CM-X270. More information about using MTD on CM-X270 can be found at [[Linux MTD drivers on CM-X270]] page.
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| − | Recently we discovered that certain NAND flash chips are not tolerant to '''any''' activity on local bus during flash accesses. To overcome this limitation we added an option to NAND flash drivers that allows to ensure there is no bus activity at the time NAND flash is active. This option can be switched on and of with {{parameter|block_irqs}} parameter of the NAND flash driver.
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| − | === I2C and SPI ===
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| − | Standard I2C and SPI drivers can be used to access these buses on CM-X270. The I2C drivers are present in Linux kernel 2.6.16, and can be easily enabled using Linux kernel configuration.
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| − | As for the SPI drivers, they should be backported to Linux kernel 2.6.16 from 2.6.17 or more recent kernel version.
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| − | === USB device ===
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| − | USB device controller drivers for PXA270 are not available in mainline kernels, and this is the main reason we do not support USB device functionality on CM-X270. Yet, there several patches available at [http://www.rpsys.net/openzaurus/patches/ http://www.rpsys.net/openzaurus/patches/], [http://handhelds.org/cgi-bin/cvsweb.cgi/linux/kernel26/drivers/usb/gadget/ Handhelds.org], [http://raph.people.8d.com/armcore_kernel.php Raphael Assenat site] dedicated to Linux on CompuLab boards, and probably others. We never tried these patches, and we don't know which of them will work on CM-X270.
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| − | == Linux kernel 2.6.24 ==
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| − | The CM-X270 platform support was merged into mainline kernel starting from version 2.6.24. There are still some features that are not present in mainline kernel. Most of these features are available in preliminary release of [http://www.compulab.co.il/mediawiki/files/Linux/x270cm/linux-2.6.24-cm-x270.tar.gz Linux kernel 2.6.24 for CM-X270] (source code only).
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| − | === Preliminary release of Linux kernel 2.6.24 for CM-X270 ===
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| − | * Fixes to suspend/resume functionality
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| − | * Change serial port mappings to ensure consistency between CM-X270L and CM-X270W
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| − | * Support for UART device integrated into PCI bridge
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| − | * Support for Marvell 8686 wireless LAN
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| − | ==== Known problems ====
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| − | * PCI bridge does not always properly resume
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| − | === Using mainline Linux kernel 2.6.24 on CM-X270 ===
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| − | It is possible to use mainline Linux kernel 2.6.24 on CM-X270 "as is". Just keep in mind that the on-board NAND flash can be accessed only using [[Linux MTD drivers on CM-X270|MTD drivers]] and the serial ports map to different {{parameter|ttys}} on L and W variants as summarized in the below table:
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| − | {| style="border: 1px #555555 solid; border-collapse: collapse" border="1" cellpadding="3px"
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| − | |+ Serial ports mapping on CM-X270'''L'''
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| − | ! UART || SB-X270 port name || Linux tty in 2.6.16 || Linux tty in 2.6.24
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| − | |-
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| − | | BTUART || COM-A || ttySA0 || ttyS1
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| − | |-
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| − | | FFUART || COM-B || ttySA1 || ttyS0
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| − | |-
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| − | | STUART || COM-D || ttySA2 || ttyS2
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| − | |-
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| − | | ITE8152 UART || COM-B || ttyS0 || not present
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| − | |}
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| − | {| style="border: 1px #555555 solid; border-collapse: collapse" border="1" cellpadding="3px"
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| − | |+ Serial ports mapping on CM-X270'''W'''
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| − | ! UART || SB-X270 port name || Linux tty in 2.6.16 || Linux tty in 2.6.24
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| − | |-
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| − | | FFUART || COM-A || ttySA0 || ttyS0
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| − | |-
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| − | | BTUART || COM-D || ttySA1 || ttyS1
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| − | |-
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| − | | STUART || COM-C || ttySA2 || ttyS2
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| − | |-
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| − | | ITE8152 UART || COM-B || ttyS0 || not present
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| − | |}
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| − | == See also ==
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| − | * [[Getting started with Linux on CM-X270]]
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| − | * [[Linux Development for XScale modules]]
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| − | * [[Debian Linux for CM-X270]]
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| − | * [[Linux MTD drivers on CM-X270]]
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